Ventricular Septal Defect with Pulmonary Stenosis or Atresia

Developmental Considerations

TF with pulmonary stenosis encompasses a wide spectrum of morphologic subsets that vary primarily in details of RV outflow obstruction, VSD, and aortic overriding. All four major components of TF—RV outflow obstruction, VSD, overriding aorta, and RV hypertrophy—are linked embryologically. Van Praagh has advanced the concept of TF being the result of a “monology.” The concept is that a small-volume subpulmonary infundibulum is the basic anomaly, resulting in pulmonary outflow tract obstruction (stenosis or atresia). There is a VSD because the small-volume infundibulum cannot fill the space above the trabecula septomarginalis (septal band; TSM) and the ventricular septum. The infundibular septum is malaligned anterosuperiorly above the RV (compared with normal) because of failure of normal expansile growth of the infundibulum. Failure of normal expansile growth of the infundibulum means that the infundibular outflow tract floor—the infundibular septum—fails to expand in a rightward, posterior, and inferior direction, thereby helping to close the interventricular foramen. Failure of this normal morphogenetic movement of the infundibular septum results in aortic overriding. Because the infundibular septum is abnormally anterosuperiorly malaligned above the RV, so too is the aortic valve, which is attached to what should be the LV outflow tract surface of the infundibular septum. RV hypertrophy is a secondary response to resulting RV afterload.

Thus, Van Praagh posits that embryologically, TF is a conotruncal malformation in which conotruncal septation is complete, but the infundibular septum is displaced. This anterior displacement is responsible for all of the morphologic characteristics of TF: crowding of the RV outflow tract and obstruction, overriding of the aorta, malalignment VSD, and RV hypertrophy.

Anderson, in contrast, argues that the “monology” concept is an oversimplification. His studies suggest two morphologic abnormalities that he considers pathognomonic for the lesion. (1) There is anterocephalad deviation of the outlet septum, but for obstruction of the RV outflow tract to occur, there must additionally be (2) an associated malformation of the septoparietal trabeculations, the muscular bars that reinforce the parietal wall of the RV. The squeeze produced between the malaligned outlet septum and the abnormally arranged septoparietal trabeculations identify the morphologic entity of tetralogy of Fallot.

Right Ventricular Outflow Tract

Infundibulum

Infundibular stenosis associated with specific alterations in position of the infundibular septum is the hallmark of TF. Specifically, the septal (leftward) end of the infundibular septum is displaced anteriorly, inserting in front of the left anterior division of the TSM (septal band) ( Fig. 38-1 ) rather than between its two divisions, as in the normal heart (see Chapter 1 , Fig. 1-5 ). In addition, the parietal (rightward) end of the infundibular septum is rotated anteriorly and passes anteriorly and inferiorly to reach the free wall of the RV ( Fig. 38-2 ), so that the infundibular septum and its parietal extension may come to lie almost in a sagittal rather than the usual coronal (frontal) plane. Parietal and septal ends of the infundibular septum give rise to prominent muscle bands that attach to the right and left sides of the anterior RV free wall. The anterior free wall may show additional trabeculations or moderate thickening.

There is frequently a localized narrowing, the os infundibulum , which in 72% of cases lies in a transverse plane at the lower infundibular septal edge (see Fig. 38-2 ). This siting means that when the infundibular septum is well developed, there is a large infundibular chamber (or “third ventricle”; see Fig. 38-2 ), which in older patients occasionally becomes aneurysmal. In older patients, however, the os infundibulum is surrounded by fibrosis, which, when the chamber is small or absent, may extend into the RV–pulmonary trunk junction (pulmonary “anulus”). Less commonly (about 15% of cases), the major stenotic zone at the lower infundibular septal edge lies almost in a coronal plane, extending inferiorly from the lower infundibular septal edge. This occurs when hypertrophied muscle bands at the parietal end of the infundibular septum pass more inferiorly to join the free wall nearer to the RV apex, while on the septal (medial or leftward) aspect, there are not only inferiorly directed additional trabeculae, but also often an undue prominence and hypertrophy of TSM. Under these circumstances the inferior boundary of the os infundibulum may be formed by a prominent superiorly displaced moderator band. (When this type of low-lying infundibular stenosis is associated with a small or moderate-sized VSD, it is not termed TF; see Section V .) Both transverse and coronal plane stenoses are occasionally present.

When an infundibular chamber is present, its walls laterally and medially consist of numerous trabeculated spaces, some of which may form prominent blind recesses that do not lead directly to the valve “anulus,” and occasionally an accessory opening is present. Endocardial fibrosis is not seen during the first 6 to 9 months of life and is seldom marked before age 2 years. Later, fibrosis seems to progress, which may lead to acquired infundibular atresia.

Generally, the infundibulum is somewhat longer, relative to total RV length, than it is in normal hearts. When the infundibular septum is short (hypoplastic), infundibular stenosis reaches the pulmonary valve “anulus” without an intervening chamber. When the infundibular septum is absent, the VSD is juxta-arterial (doubly committed), extending superiorly to reach the pulmonary valve; infundibular stenosis is absent, and the posterior aspect of the RV outflow tract is formed by the VSD ( Fig. 38-3 ). The pulmonary valve and sometimes its “anulus” are the main sites of the usually moderate stenosis in these hearts. However, once a VSD patch is in position, the hypertrophied RV walls and dextroposed aorta may combine with the patch to form severe subvalvar stenosis.

The infundibulum may be diffusely narrowed and hypoplastic. This is usually associated with severe cyanosis at birth or shortly thereafter. There is no localized os infundibulum ( Fig. 38-4 ) nor increased trabeculations, nor important muscular hypertrophy. Nevertheless, stenosis is usually severe because narrowing occurs throughout the outflow tract ( Fig. 38-5 ). Length of the stenosis in this morphologic variant is determined by length of the infundibular septum (see Fig. 38-4 ).

Pulmonary Valve

The pulmonary valve is stenotic to some degree in 75% of patients with TF. Approximately two thirds of stenotic valves are bicuspid ( Table 38-1 ). A three-cusp configuration occurs more commonly in nonstenotic valves. Even when nonstenotic, valve area is usually smaller than that of the aortic valve, which is the reverse of normal. The difference in size of these two valves is partly because the pulmonary valve is small and partly because the aortic valve is larger than normal.

Table 38-1

Pulmonary Valve Morphology in Tetralogy of Fallot ^a

Morphology	n	%
Valve Configuration
Bicuspid	93	66
Three-cusp	21	15
Vestigial	14	10
Not recorded	13	9
T otal	141	100
Valve Lesion
Tethering alone	89	63
Commissural fusion alone	20	14
Tethering + fusion	8	6
Vestigial valve	14	10
Atretic valve (acquired)	2	1
Not recorded	8	6
T otal	141	100

a Based on 141 patients undergoing repair (GLH experience, 1968-1978) of tetralogy of Fallot with pulmonary stenosis (excluding patients with subarterial ventricular septal defect, absent pulmonary valve, or congenital pulmonary atresia).

Stenotic valve cusps are usually thickened, frequently severely so, a feature that increases the amount of obstruction at the valve level ( Fig. 38-6 ). In approximately 10% of cases, cusps are replaced by sessile nubbins of fibromyxomatous tissue that offer little obstruction. Such vestigial valves are usually associated with a stenotic pulmonary “anulus.” When the “anulus” is not severely narrowed and the valve is vestigial, severe pulmonary regurgitation results, a condition called TF with absent pulmonary valve (see Section III ).

Pulmonary valve stenosis is usually caused by cusp tethering rather than by severe commissural fusion (see Table 38-1 ). The free edge of tethered cusps is considerably shorter than the diameter of the pulmonary trunk, so the valve cannot open adequately, and the pulmonary trunk is pulled inward at the point of commissural attachment. This produces a localized narrowing or corseting of the trunk at distal valve level. Thus, both the valve and trunk are tethered (see Fig. 38-6 ). In this situation the sinuses of Valsalva are frequently well formed, but entry into them between the cusp edge and pulmonary trunk wall is often also stenotic, resulting in slow filling of the sinuses with contrast medium on cineangiography. Cusps of a tethered valve may be fused for a short distance. Tethering is more common in a bicuspid valve, but can occur in a three-cusp valve.

Less commonly, the dominant morphology is thickened cusps associated with congenital commissural fusion, resulting in a concentric or eccentric stenotic orifice. An eccentric orifice can also result from a unicuspid configuration.

A fused stenotic pulmonary valve orifice may be beaded with tiny “vegetations” of fibrin. Progressive deposition of fibrin is presumably the mechanism of acquired valvar atresia.

Pulmonary Trunk

Like the pulmonary valve and “anulus,” the pulmonary trunk is nearly always smaller than normal, and smaller than the aorta. Reduction is most marked when there is diffuse RV outflow hypoplasia. Then, the pulmonary trunk is less than half the aortic diameter and is short (see Fig. 38-6 ), directed sharply posterior to its bifurcation. It is thus largely hidden from view at operation by the prominent aorta, which also displaces the origin of the trunk leftward and posteriorly.

When the pulmonary valve is markedly tethered, the pulmonary trunk is also tethered or corseted at its commissural attachments (see Fig. 38-6 ), and it may be very angulated or kinked at this point. This is the usual mechanism of supravalvar narrowing, and it is not associated with wall thickening. Rarely, however, there may be a discrete supravalvar narrowing beyond commissural level with diffuse wall thickening.

Pulmonary Trunk Bifurcation

The left pulmonary artery (LPA) is usually a direct continuation of the pulmonary trunk, with the right pulmonary artery (RPA) arising almost at right angles and close to it, but this pattern varies ( Fig. 38-7 ). Uncommonly, the distal pulmonary trunk and origin of the RPA and LPA are moderately or severely narrowed (bifurcation stenosis), and in this situation the bifurcation may have a Y shape. A Y-shaped bifurcation is more common when the ductus arteriosus is absent (see “ Aortic Arch and Ductus Arteriosus ” later in this section).

Right and Left Pulmonary Arteries

Anomalies of the RPA and LPA are common in TF with pulmonary atresia (see Section II ) but uncommon in TF with pulmonary stenosis, although any of the anomalies present in pulmonary atresia may occur in patients with pulmonary stenosis ( Table 38-2 ). Fellows and colleagues found pulmonary artery anomalies in 30% of infants having TF with pulmonary stenosis presenting in the first year of life. In particular, proximal LPA stenosis or hypoplasia, or both, can occur when certain configurations of the ductus arteriosus are present (see “ Aortic Arch and Ductus Arteriosus ” later in this section).

Distal Pulmonary Arteries and Veins

Pulmonary arteries and veins beyond the hilar positions are about normal in size in most patients. Intraacinar arteries are smaller than normal, and their media are thinner. In addition, lung volume, alveolar size, and total alveolar number tend to be reduced.

Dimensions of Right Ventricular Outflow Tract and Pulmonary Arteries

Hypoplasia of the RV outflow tract and pulmonary arteries in patients having TF with pulmonary stenosis is most marked centrally in the RV infundibulum and pulmonary trunk. On average, the RPA and LPA and their branches are not abnormally small. This does not deny the occasional existence of severe narrowing at the origin of the LPA or RPA (see Fig. 38-7 ). Elzenga and colleagues found juxtaductal proximal stenoses of the LPA in 10% of patients having TF with pulmonary stenosis. There is great variability in these dimensions, however, making their careful pre-repair study important.

Convenient Morphologic Categories of Right Ventricular Outflow Obstruction

The nearly infinitely variable spectrum of RV outflow obstruction in TF can be conveniently categorized in a way that is surgically useful because it relates to difficulty in obtaining good relief of the pulmonary stenosis and therefore to surgical techniques and mortality ( Box 38-1 ). This supplements earlier discussion of patterns of the infundibular portion of the obstruction. It might be inferred that transanular patching to relieve outflow tract obstruction would be more frequently required in those with “anulus” stenosis or diffuse hypoplasia, but a blanket rule is probably inappropriate.

Iatrogenic Pulmonary Arterial Problems

A transanular patch may later produce severe stenosis at the origin of the LPA or, less commonly, of the RPA. Important stenosis or kinking of an RPA or LPA may also be produced by an imprecise shunting operation (see “ Technique of Shunting Operations ” later in this section). The distal pulmonary artery may then become relatively hypoplastic because of poor pulmonary blood flow ( ).

Collateral Pulmonary Arterial Blood Flow

Patients virtually always have increased collateral pulmonary arterial blood flow, primarily from true bronchial arteries. Occasionally (less than 5% of patients), large aortopulmonary (AP) collateral arteries are present (see detailed discussion in “ Alternative Sources of Pulmonary Blood Flow ” in Section II ).

Ventricular Septal Defect

In classic TF, the VSD is juxta-aortic and usually lies adjacent to or involves the membranous septum (conoventricular and perimembranous). It differs from the usual isolated VSD, however, in that it is associated with malalignment of the infundibular septum (see Fig. 38-2 ) and is virtually always large. Anterior displacement (malalignment) of the infundibular septum relative to the crest of the ventricular septum creates the VSD, rather than a deficiency of tissue. The infundibular septum may or may not be deficient or hypoplastic (see next paragraph), but deficiency of tissue is not necessary for the VSD to be present

The defect is more U-shaped than circular and is bounded superiorly and anteriorly by the free edge of the infundibular septum (see Fig. 38-4 ). The septum may support part or most of the right aortic cusp, depending on the degree of aorta overriding the RV (see Fig. 38-1 ). Because of the anterior and leftward deviation of the parietal end (parietal extension) of the infundibular septum, the posterosuperior angle of the defect extends higher than that of the usual isolated conoventricular VSD (see Fig. 38-2, A ) and can be more difficult to expose surgically, particularly if the parietal band is not fully mobilized (transected). When the infundibular septum is hypoplastic, the defect is larger and extends closer to the pulmonary valve; when the infundibular septum is absent, the VSD becomes juxtapulmonary (and juxta-arterial).

Posterosuperiorly, the VSD is bounded by muscle (the ventriculoinfundibular fold) adjacent to the rightward edge of the noncoronary aortic cusp ( Fig. 38-8 ). This cusp may override considerably onto the RV ( Fig. 38-9 ); then, the LV-aortic junction adjacent to the noncoronary cusp forms this boundary.

The posterior margin is variable. It is related to the base of the tricuspid anteroseptal leaflet commissure and to the right fibrous trigone (central fibrous body) at the nadir of the noncoronary aortic cusp. There is tricuspid-aortic-mitral fibrous continuity at this margin, and the membranous septum is absent—characteristics of a true perimembranous VSD. In some hearts the VSD extends inferiorly beneath the tricuspid septal leaflet more than usual, described as “inlet extension” of the VSD. When there is marked clockwise rotation of the overriding aortic root, the right trigone may form the posteroinferior angle of the defect, and the bundle of His (which perforates at this point) is exposed along the edge of the defect ( Fig. 38-10 ). Occasionally the posterior margin may be formed by a remnant of fibrous tissue (membranous septum) projecting upward from the right trigone region. This tissue, also called the membranous flap , does not contain conduction tissue, and it can receive some of the sutures used to secure the VSD patch. Suzuki and colleagues found such a flap in about half of 158 TF hearts. Kurosawa and Imai found at least a remnant in all 68 of their surgical cases. In at least 20% of hearts, the posterior margin is formed by a muscular ridge of variable size that separates the right trigone from the base of the anterior tricuspid leaflet. This ridge is formed by the right posterior division of the TSM as it becomes continuous with the ventriculoinfundibular fold ( Fig. 38-11 ; see also Fig. 38-8 ). It displaces the right trigone and therefore the bundle of His away from the defect edge.

The inferior margin of the VSD is formed by the TSM as it cradles the VSD between its limbs. The papillary muscle of the conus (or corresponding chordae only) arises from the right posterior division of the TSM at the anteroinferior angle of the defect. Anomalous tricuspid chordal attachments to other margins of the defect are rare, in contrast to the situation in isolated perimembranous VSD.

The anterior margin of the VSD is formed by the leftward anterior division of the TSM as it becomes continuous with the inferior margin of the infundibular septum. When the TSM is poorly developed, the defect extends further anteriorly, and the VSD is described as having “anterior extension.”

When the infundibular septum is absent, the VSD is juxta-arterial and is described as having “outlet extension.” Posteriorly, this type of VSD is commonly separated from the tricuspid anulus by a 2- to 5-mm strip of muscle, but it may extend to the anulus. Aortic and pulmonary valve “anuli” are contiguous over about one third of their circumferences, being separated at this point by only a thin fibrous ridge where the infundibular septum would have been, if present (see Fig. 38-3 ). The two valves are often side by side, with the aorta more than usually dextroposed. TF with this type of VSD is morphologically similar to double outlet RV with a doubly committed (juxta-arterial) VSD (see Chapter 53 ), with the important distinction that in TF, fibrous continuity is maintained between the aortic valve and the central fibrous body, whereas in double outlet RV there is infundibular muscle beneath the aortic valve, and thus there is fibrous discontinuity between the aortic valve and central fibrous body.

In 3% to 15% of patients (see Table 38-2 ), one or more additional VSDs coexist with the typical juxta-aortic one ( Fig. 38-12 ). Usually the additional VSD is muscular, and multiple muscular defects sometimes occur. It may also be in the inlet septum, either as an inlet septal VSD or a muscular defect (see “Inlet Septal Ventricular Septal Defect” under Morphology in Section I of Chapter 35 ).

Conduction System

The sinus and atrioventricular nodes are in their normal locations (see “Conduction System” in Chapter 1 ), and the bundle of His follows the same general course as in patients with isolated perimembranous VSDs (see “Location in Septum and Relationship to Conduction System” under Morphology in Section I of Chapter 35 ). Thus, the His bundle emerges through the right fibrous trigone at the base of the noncoronary cusp of the aortic valve and courses forward toward the papillary muscle of the conus along the inferior VSD margin or slightly to the left side of the defect edge. In hearts showing marked clockwise rotation of the aortic root with RV overriding, the right trigone (and along with it the penetrating portion of the His bundle) is carried more rightward and superiorly and directly onto VSD margins (see Fig. 38-10 ).

By contrast, the bundle of His does not lie on the VSD margin when a muscle ridge is present (see Figs. 38-8 and 38-11 ), because the ridge projects superiorly above the right fibrous trigone; when the ridge is bulky, sutures can be safely placed into it.

Aorta

The aorta is biventricular in origin and more anteriorly placed than normal, often almost obscuring the smaller pulmonary trunk from view at operation. These changes are due to RV overriding, rotation, and enlargement of the aortic root. The proportion of aorta lying above the RV varies between 30% and 90%. Generally, about 50% of the aortic orifice is over the RV.

Aortic overriding is associated with a variable degree of clockwise rotation of the aortic root (as viewed from below). This rotation moves the base of the noncoronary cusp rightward and superiorly onto the posterosuperior margin of the VSD and away from the base of the anterior mitral leaflet so that in extreme cases, it may no longer be continuous with this structure. This cusp may then lie in part just beneath the extension of the infundibular septum. Rightward rotation of the left aortic cusp results in more of it becoming continuous with the anterior mitral leaflet. Simultaneously, the superiorly positioned right cusp moves to the left, and in extreme examples it may be just beneath the uppermost extension of the left anterior division of the trabecula septomarginalis at the anterosuperior VSD margin. An important point is that, despite the degree of aortic rotation, continuity of some portion of the aortic “anulus” and the anterior mitral leaflet is always maintained. As a result the VSD is always related to the aorta in TF. The VSD may also be related to the pulmonary valve when the infundibular septum is absent (see “ Ventricular Septal Defect ” in this section).

Degree of overriding and clockwise rotation of the aortic root relates to degree of underdevelopment of the RV outflow tract and to deviation (malalignment) of the infundibular septum. When these are minimal, as seen with isolated low-lying infundibular stenosis, the aorta is minimally affected; when there is diffuse RV outflow tract hypoplasia in association with a small, markedly deviated infundibular septum and posterior and leftward movement of the pulmonary trunk origin, the aorta is markedly rotated and dextroposed.

In patients with severe TF, the aortic root is larger than normal, even in infants. Occasionally in adults, it is greatly dilated. This may result in aortic valve regurgitation.

Aortic Arch and Ductus Arteriosus

The ductus arteriosus is absent in about 30% of patients born with TF. This does not mean a closed ductus (ligamentum arteriosum), but rather complete absence of any ductal structure. Absence of the ductus or ligamentum is about twice as common when there is a right, rather than left, aortic arch. The pulmonary artery bifurcation often takes on a Y-shaped configuration, also described as the “staghorn” or “seagull” configuration, in this setting. In the other 70% of patients in whom a ductal structure is present, it is patent at birth and closes over a normal time course unless pharmacologically maintained with PGE ₁ for therapeutic reasons (cyanosis). The configuration of the ductus can vary from normal (an extension of the pulmonary trunk, creating an arch that somewhat parallels the aortic arch and inserts into the distal aortic isthmus) to abnormal, approximating the ductus orientation seen in pulmonary atresia (arising from the LPA and inserting more proximally into the aortic arch, without forming an arch). When the RV outflow tract obstruction is mild or moderate, the ductal configuration is more normal, reflecting ductal flow from the pulmonary trunk to aorta during fetal life, and more like that in pulmonary atresia when the RV outflow tract obstruction is severe, reflecting ductal flow from aorta to pulmonary trunk during fetal life. When the ductus originates from the LPA, the short proximal segment of LPA between the pulmonary trunk and ductus may be hypoplastic, and the LPA at the ductus insertion may become stenotic or even occluded when the ductus closes (so-called LPA coarctation). Rarely, there is physical discontinuity between the LPA and pulmonary trunk, with the isolated LPA arising from the ductus or ligamentum ( Fig. 38-13 ).

A left aortic arch is present in about 75% of patients. In these, arch branching pattern is usually normal.

A right aortic arch is present in about 25% of patients. In 90% of these, there is mirror-image branching of the arch. Should a patent ductus arteriosus be present, it usually arises from the brachiocephalic or proximal left subclavian artery and joins the LPA. Rarely, there may be a right-sided ductus arteriosus to the RPA, usually arising from the upper descending thoracic aorta. In about 10% of patients, there is an aberrant left subclavian artery, analogous to the aberrant right subclavian artery of dysphagia lusoria in left aortic arch (see “Right Aortic Arch with Aberrant Left Subclavian Artery” in Section I of Chapter 51 ). In right aortic arch with aberrant left subclavian artery, the subclavian artery may arise directly from the descending aorta or from an aortic diverticulum. Thus, a ductus arteriosus may arise from the aortic diverticulum and pass to the left behind the esophagus to join the LPA.

Rarely, the left subclavian artery is sequestered or isolated from its aortic arch origin, but remains connected to the LPA by a patent ductus arteriosus. Often in these circumstances, there is vertebral steal, and on angiography the subclavian artery fills with contrast from the vertebral artery.

Right Ventricle

External dimensions of the sinus (inflow) portion of the RV are larger than normal due to hypertrophy, so the interventricular groove is displaced leftward and the LV lies more posteriorly than usual (clockwise rotation of ventricles). The RV sinus may be clearly separated from the infundibulum during systole by a transverse depression representing the site of maximal infundibular stenosis inferior to an infundibular chamber. RV wall thickness equals that of the LV and is therefore never excessive unless the large VSD is made restrictive by a fibrous flap valve on its right side (see Section IV ). Normal trabeculations are, however, bulky and prominent. RV end-diastolic volume may be reduced and ejection fraction mildly depressed, typically in older children without TF repair, possibly the result of chronic hypoxia. Rarely (1.5% of cases), the sinus portion of the RV and tricuspid valve are underdeveloped (see Table 38-2 ).

Left Ventricle

The LV is usually normal in wall thickness but variable in volume. In patients with severe forms of TF with severe cyanosis, LV end-diastolic volume is normal or somewhat small, but wall thickness remains normal. Uncommonly, the LV and mitral valve are truly hypoplastic, and rarely this may be so severe (end-diastolic volume < 30 mL · m ⁻² ) as to contraindicate primary repair.

The physiologic contributors to LV size are complex. The small pulmonary and thus left atrial blood flow tend to result in a small left atrium and LV. However, the RV ejects blood into the LV as well as the aorta, and this tends to increase LV size. Mild or moderate degrees of LV hypoplasia may result from these physiologic factors, but true hypoplasia is of morphologic rather than functional origin.

LV systolic function is normal at birth but may become mildly reduced in older patients who have not undergone repair, particularly in severely cyanotic patients, presumably because of chronic hypoxia.

Coronary Arteries

As in other cyanotic conditions, the coronary arteries become dilated and tortuous in children and adults. A large conal branch of the right coronary artery (RCA) usually courses obliquely across the free wall of the RV, and the presence of this vessel should be noted at the time of surgical repair.

The left anterior descending coronary artery (LAD) arises anomalously from the RCA in about 5% of patients ( Table 38-3 ). The entire LAD may originate from the RCA and cross the anterior wall of the infundibulum a variable distance from the pulmonary valve, or only the distal part of the LAD may arise anomalously, in this case usually from the large conal branch of the RCA.

Rarely, the RCA originates from the left coronary artery, and equally uncommonly, there is anomalous origin of the left coronary artery from the pulmonary trunk (see Section II of Chapter 46 ).

Major Associated Cardiac Anomalies

Major associated cardiac anomalies are relatively uncommon (see Table 38-2 ). Patent ductus arteriosus, multiple VSDs , and complete atrioventricular septal defect are most often seen.

Rarely, the RPA or LPA arises anomalously from the ascending aorta (see Chapter 45 ). This complicates the pathophysiology and repair, because the lung supplied by the pulmonary artery arising from the aorta usually has overcirculation, and the other usually has restricted flow due to the intracardiac anatomy.

Infrequently, aortic valve regurgitation coexists. This may be from typical cusp prolapse in TF with subarterial VSD (see Section II in Chapter 35 ). A bicuspid aortic valve occurs rarely in TF and may result in aortic regurgitation. Occasionally, ill patients with TF in the second decade of life or older develop aortic regurgitation from endocarditis. Massive dilatation of the aortic root from anuloaortic ectasia may result in aortic valve regurgitation, particularly in patients with large natural or surgically created systemic–pulmonary arterial shunts (see “Anastomotic” under Morphology in Chapter 26 ).

Minor Associated Cardiac Anomalies

Most infants undergoing repair of TF have a patent foramen ovale (PFO); when all ages are considered, a true atrial septal defect is found at operation in about 10%. Other minor associated cardiac anomalies are listed in Table 38-3 .

Clinical Presentation

The hallmark clinical sign of TF is cyanosis. The severity of cyanosis and its variability depend on the specific morphology of the RV outflow tract. Infants with diffuse RV outflow hypoplasia, severe infundibular plus valvar plus anular stenosis, or severe infundibular plus valvar stenosis (see Box 38-1 ) are deeply cyanotic from birth and do not develop heart failure. They are breathless on feeding or other exertion. Hypoxic spells are rare, the cyanosis being constant and gradually worsening. It is seldom lessened by propranolol.

This situation contrasts with that in infants having dominant infundibular stenosis, in which onset of cyanosis is delayed and hypoxic (cyanotic) spells due to infundibular spasm may occur. These spells are often prevented or lessened in frequency by propranolol. Characteristically, they become less frequent with age, presumably because stenosis becomes fixed as a result of acquired endocardial fibrosis and thickening.

In up to 10% of patients who require surgical relief in infancy, presentation is initially as a large VSD with pulmonary plethora and sometimes heart failure at age 2 to 3 months, followed by gradually increasing cyanosis, frequently with cyanotic spells, at about age 6 months. In this group, stenosis is purely infundibular.

A minority of patients are acyanotic at rest and only mildly cyanotic during exercise because pulmonary stenosis is mild and right-to-left shunting minimal. In some the shunt is predominantly left to right. These individuals may remain acyanotic without spells and present at any age within the first or second decades of life with gradually increasing cyanosis and breathlessness as stenosis slowly increases in severity.

In patients with severe cyanosis and polycythemia, cerebral thrombosis may precipitate hemiplegia at any age (particularly in association with dehydration), or hemiplegia may follow paradoxical embolism or a brain abscess. The latter is heralded by fever, headache, and sometimes seizures. Massive hemoptysis may occur in older patients who are severely cyanotic, presumably from rupture of bronchial collateral vessels.

Cyanosis is always accompanied by effort dyspnea that is sometimes the dominant symptom, and as the child begins to walk (frequently much later than for a healthy child), cyanosis is often accompanied by squatting, which lessens its severity. There may be increased occurrence of respiratory infection, but not to the same extent as in patients with large isolated VSD; failure to thrive is also less striking.

Physical Examination

Cyanosis of variable degree is generally evident. Deeply cyanotic infants are often obese (in contrast to infants with isolated VSD). Severe symmetric clubbing of the fingers and toes is often present in children and adults, but not in infants. Older patients may also have marked acne of the face and anterior chest. Jugular venous pressure is normal. The heart is not enlarged and is relatively quiet with an unimpressive RV lift. In those few patients with increased , the lift may be more marked than usual.

A precordial systolic thrill is rare. There is a moderate-intensity midsystolic pulmonary (ejection) murmur maximal in the second and third left intercostal spaces that becomes less prominent or even disappears when the stenosis is severe. When there is still a reasonable blood flow in the presence of moderate pulmonary stenosis, the systolic murmur is well heard posteriorly and in the axilla. In the presence of important cyanosis and low , the second heart sound is single, but in acyanotic patients it may be finely split with a low-intensity pulmonary component. Splitting is also present in moderately cyanotic patients with only a mildly reduced when there are important pulmonary artery origin stenoses.

Signs of heart failure with venous pressure elevation and liver enlargement occur in patients with a systemic-to–pulmonary arterial shunt that is too large, or in a neonate on PGE ₁ to maintain ductal patency. Heart failure may also appear in untreated severely cyanotic adults in the fourth or fifth decade of life, presumably secondary to myocardial fibrosis or in association with systemic hypertension or aortic regurgitation.

Laboratory Studies

Neonates or young infants who have severe TF with pulmonary stenosis usually present with marked reduction of arterial oxygen pressure (Pa o ₂ ) and saturation (Sa o ₂ ) and sometimes with metabolic acidosis. Polycythemia is rarely present, and, in fact, such infants are often anemic.

In older infants and children, red blood cell count and hematocrit are usually elevated, and degree of elevation is correlated with degree of arterial desaturation and thus with severity of the pulmonary stenosis. In older patients, hematocrit may reach 90%.

Most cyanotic patients have depressed platelet count and prolongation of most coagulation tests.

Chest Radiography

Chest radiographs in children usually show the typical boot-shaped heart of TF. In neonates and young infants the heart may be strikingly small, with an absent pulmonary artery segment along the left upper cardiac border and oligemic lung fields. In older patients, there may be a prominence of the left upper cardiac border caused by a large infundibular chamber. Large AP collaterals may alter the pulmonary blood flow pattern in one or both lungs. Plethora of one lung and oligemia of the other suggest anomalous origin of a pulmonary artery from the ascending aorta (see Chapter 45 ).

If there is a right aortic arch, posterior indentation of the shadow of the barium-filled esophagus results from an aberrant left or right subclavian artery.

Rib notching of the upper ipsilateral ribs may develop in the presence of a long-standing classic Blalock-Taussig (B-T) shunt, secondary to development of a rich collateral blood flow to the arm. This situation is rarely encountered in the current era because the classic B-T shunt is not commonly performed. Presumably, the same pathophysiology could develop after a modified B-T shunt if the subclavian artery were severely stenotic or occluded. Rarely, collaterals from the pleura to the lung may be sufficiently large, especially after poudrage or pleural stripping procedures, to result in bilateral rib notching in the lower half of the thorax. Patients in the second or third decade of life may show progressive kyphoscoliosis.

Electrocardiography

Electrocardiography (ECG) shows moderate RV hypertrophy consistent with RV pressure that is equal to but not greater than systematic pressure (in contrast to flap valve VSD; see Section IV ). Occasionally, there is minimal RV hypertrophy, and in these circumstances RV underdevelopment should be suspected, although it may not be present. Left precordial leads are characterized by absent Q waves and low-voltage R waves. Occasionally the frontal plane vectorcardiographic pattern characteristic of atrioventricular septal defect is found in patients with typical TF.

Echocardiography

Echocardiography is considered the definitive diagnostic procedure of choice in neonates and infants. The VSD, atrial septal status, aortic overriding, narrowing of the RV infundibulum, pulmonary valve, pulmonary trunk and bifurcation into the branch pulmonary arteries, and the ductus arteriosus, if present, can usually be seen with ECG ( Fig. 38-14 ). Also, in experienced hands, two-dimensional (2D) echocardiography with Doppler color-flow interrogation has the same sensitivity and specificity for multiple VSDs in TF as does cineangiography. However, morphologic details of distal pulmonary artery branches as they approach the hilum may not be reliably visualized. Additional imaging is indicated when important abnormalities of the branch pulmonary arteries are identified, such as hypoplasia, discontinuity, or stenosis, and when abnormal arterial signals on Doppler interrogation are identified in the central and posterior mediastinum, suggestive of major AP collaterals.

Color Doppler imaging can also provide important physiologic information. Accurate estimates of the severity of obstruction across the RV outflow tract, as well as the site of obstruction (infundibular, valvar, supravalvar), can be obtained. Flow characteristics across the VSD and LV outflow tract can be used to confirm that pressures in the RV and LV are equal. Systolic function of the ventricles and competency of the inlet valves are also easily assessed, and flow patterns across the inlet valves in diastole can provide important information about ventricular diastolic function. In most cases the coronary artery pattern can be characterized, and anomalous patterns, such as the LAD arising from the RCA, can be identified.

Newer modalities of echocardiography, such as 3D echo, tissue Doppler, and strain rate imaging, hold further promise as noninvasive tools for improved morphologic and functional evaluation. Echocardiography can effectively diagnose TF in the fetus, and can be helpful in planning early surgical intervention and in parental counseling.

In patients who have undergone operation for TF, whether palliative procedures or definitive repair, and in unoperated TF patients presenting well beyond infancy, echocardiography is an important part of the diagnostic workup; however, it is not definitive. Characterizing pulmonary vascular resistance (Rp) and imaging the distal pulmonary arteries require cardiac catheterization.

Cardiac Catheterization and Angiography

Preoperative cardiac catheterization and angiography, although not routinely required when expertly interpreted echocardiography is available, precisely portray the hemodynamic state and morphology, particularly that of the distal pulmonary arteries. Peak pressure in the RV cavity (P rv ) is similar to that in the left (P lv ), and pulmonary artery pressure (P pa ) is below normal. A systolic pressure gradient is demonstrable at infundibular and valvar levels when both zones are stenotic, but rarely at a more peripheral site. When proximal stenoses are severe, however, it may be impossible to enter the pulmonary trunk with a catheter.

There is right-to-left shunting at ventricular level and low , the severity of which reflect severity of stenosis. In acyanotic patients, there is minimal right-to-left shunting at rest or even a slight increase in , but in most patients, right-to-left shunting occurs on exercise. In severely cyanotic patients, P pa and Rp are not elevated preoperatively, even in the presence of important peripheral pulmonary artery stenosis or thrombosis, because of low . P pa may be elevated when there is a large and an increase in Rp.

Biplane cineangiography demonstrates all the morphologic features of the malformation as well as morphology and dimensions of the RV–pulmonary trunk junction, pulmonary trunk, and RPA and LPA and their branches. Oblique and angled views are used. Configuration of the RV sinus and infundibulum and degree and morphology of the RV outflow tract obstruction are studied. Morphology of the pulmonary valve and any tethering or narrowing of the pulmonary trunk at the level of the commissural attachments of the valve or beyond are noted. Bifurcation of the pulmonary trunk and origins of the LPA and RPA are studied with particular care because the surgeon cannot accurately assess presence or severity of stenoses in this area during operation. The sitting-up position (cranially tilted frontal view) generally offers the best view, although oblique views also usually demonstrate origins of both pulmonary arteries. Presence, size, and morphology of various portions of the RPA and LPA are studied with care.

With proper profiling of the ventricular septum, the typical large VSD and overlying dextroposed aorta are identified (see Fig. 38-12 ). Additional VSDs, if present, are identified as well.

Coronary arterial anatomy can usually be seen following LV injection. Particular search is made for anomalous origin of the LAD from the RCA and for the rare but surgically important associated origin of the left coronary artery from the pulmonary trunk.

Follow-through frames are examined for evidence of large AP collateral arteries, and injection is made into the thoracic aorta and/or selectively into the collateral arteries if these are present. When the true LPA or RPA is not visualized following these injections, which must include late filming and sometimes also digital subtraction techniques, a pulmonary vein wedge injection is made to fill (retrogradely) the pulmonary arterial tree ( Fig. 38-15 ). When all techniques including this one fail to outline a central or hilar portion of a pulmonary artery, it can be safely assumed to be absent.

Any major associated cardiac anomalies are identified by the study. Previous palliative shunts or transanular patches are visualized, the former by selective injections if necessary. Any iatrogenic pulmonary arterial problems are defined in detail. Particular care is taken to visualize these to help the surgeon avoid misidentifying structures during repair.

Computed Tomography

Computed tomographic angiography (CTA) is used selectively in TF, both in neonates and infants, as a preoperative diagnostic test and in patients after palliative surgery or reparative surgery. It can define the branch and peripheral pulmonary arteries accurately and has replaced conventional angiography for many clinical indications ( Fig. 38-16 ). The chief advantage is that it requires only peripheral intravenous access for contrast injection, thereby removing the risk of catheter-induced complications. Furthermore, CT images are 3D and amenable to image postprocessing ( Fig. 38-17 ), whereas images from conventional angiography are projectional and overlapping vessels can be difficult to interpret. Conventional angiography has better spatial resolution, and selective branch injections may reveal flow dynamics in collateral branches better than CTA.

At the present time, when echocardiography is not sufficient to allay concerns about peripheral pulmonary artery abnormalities, CTA may be indicated to clarify the morphology. The decision to use conventional versus CTA is partly based on institutional expertise and preference; however, if hemodynamic information is required, or if major AP collaterals are suspected, catheterization is necessary.

In neonates and infants with suspected branch pulmonary artery abnormalities on echocardiography, in whom there is usually little concern about abnormal Rp, CTA is an excellent method for defining pulmonary artery stenoses and arborization abnormalities. In patients with systemic to pulmonary artery shunts, in whom concerns about Rp abnormalities are not present, CTA can define the morphologic details of the peripheral pulmonary arteries, systemic-pulmonary collateral vessels, and their pulmonary distributions. Cardiac-gated CTA can also reveal unanticipated coronary artery anomalies associated with TF (see Fig. 38-17 ). In postrepair TF patients with residual RV outflow tract abnormalities, CT can accurately characterize the morphology from the infundibulum to the peripheral pulmonary arteries and help detect native stenosis and conduit stenosis ( Fig. 38-18 ) and aneurysm or pseudoaneurysm ( Fig. 38-19 ).

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is also used selectively in TF. Generally speaking, CTA has higher spatial resolution than MRI, and therefore CT is preferred when finely detailed peripheral pulmonary vascular morphologic information is required. MRI can accurately define the anatomy of the RV outflow tract and branch pulmonary arteries ( Figs. 38-20 and 38-21 ). MRI has the advantage that it does not use ionization radiation and is a good choice in larger patients and when repeated studies are anticipated. In neonates and infants, preoperative echocardiography is usually adequate and MRI is rarely indicated.

The major indication for MRI is in postrepair TF patients with chronic pulmonary regurgitation. RV volume, pulmonary valve regurgitant fraction, coexisting pulmonary stenosis, and tricuspid valve regurgitant fraction can all be assessed quantitatively ( Fig. 38-22 ). Serial examinations can accurately define trends in the values of these variables over time, and these trends can be helpful in determining the timing of reoperation. RV end-diastolic volume greater than 150 mL · m ⁻² in children has been identified as a threshold above which the RV is likely not to normalize its volume even after placement of a pulmonary valve prosthesis.

When pacemakers or defibrillators are present, MRI is contraindicated. Under these conditions, CTA can be an excellent alternative.

Symptoms and Survival

Twenty-five percent of surgically untreated infants die in the first year of life, but uncommonly in the first month ( Fig. 38-23, A and B ). These are the patients with the most severe obstruction to pulmonary blood flow. Forty percent are dead by age 3, 70% by age 10, and 95% by age 40. Instantaneous risk of death (hazard function) is greatest in the first year of life ( Fig. 38-23, C ). Risk then stays constant until about age 25, when it begins again to increase.

Hypoxic spells in the first few years of life are related to hyperactivity of the infundibulum. This and contraction of the infundibular septum and its parietal extension earlier in systole than in normal subjects produce variable and sometimes severe episodes of RV outflow tract obstruction and symptoms. Any sudden reduction of systemic vascular resistance also may precipitate a hypoxic spell.

About 25% of patients are acyanotic at birth and become cyanotic in the ensuing weeks, months, or years as pulmonary stenosis increases. Progression of arterial desaturation, cyanosis, and polycythemia is variable and is furthered not only by increasing pulmonary stenosis but also by widespread tendency to thrombosis of the smaller pulmonary arteries, with progressive reduction in . As part of this same tendency, death may result from cerebral thromboses or abscesses.

In those few patients surviving into the fourth and fifth decades of life, death is commonly from chronic heart failure due to secondary cardiomyopathy that results from RV pressure overload and chronic hypoxia and polycythemia.

Pulmonary Artery Thromboses

In severely cyanotic and polycythemic patients, diffuse pulmonary arterial thrombosis can occur. This is initially visible only microscopically, but rarely it progresses to occlusion of a lobar pulmonary artery or even an entire RPA or LPA. Usually, Rp is not importantly increased by this process, but rarely the thrombosis is so widespread and severe as to be a cause of immediate and sometimes fatal pulmonary hypertension and RV failure following repair.

Pulmonary Vascular Disease

Pulmonary vascular disease rarely develops in surgically untreated patients. It may develop following too large a systemic to pulmonary arterial shunt (see “ Interim Results after Classic Shunting Operations ” later in this section). When a surgical shunt appears to be the cause, it is possible that preexistent pulmonary arterial thrombosis has compounded the problem.

Genetic History

Offspring of a parent who has TF are more likely to have the anomaly than offspring of parents without congenital heart disease. It is estimated that about 0.1% of live births have TF under the latter circumstances and about 1.5% under the former.

General Plan and Details of Repair Common to All Approaches

Approach

Surgical access to the VSD and RV outflow tract through a right atriotomy, supplemented by evaluating the pulmonary valve via a pulmonary arteriotomy in most cases, is advocated by some. This approach makes sense when a well-developed infundibulum is present; however, if there is diffuse hypoplasia of the RV outflow tract, and a full-length transanular patch is anticipated, this approach makes little sense. Additionally, if a small tricuspid valve is present, exposure through the right atrium may be difficult, especially in small infants, and more damage than good may result from traction on the myocardium and tricuspid valve. Nevertheless, initial approach through the pulmonary artery and right atrium is preferred in all situations by some.

Transanular Patch

The question of whether to use a transanular patch arises in many cases, and this decision is now known to have far-reaching implications for long-term outcome. Recent publications continue to emphasize the detrimental effects of large transanular incisions. A transanular patch creates obligatory pulmonary regurgitation, and when this is long-standing and severe, important RV dysfunction will inevitably occur (see Results later in this section). Degree of narrowing of the “anulus” can be expressed quantitatively by a z value—that is, the number of standard deviations (usually smaller) from normal. When the z value has been determined from echocardiography, corrected and transformed cineangiographic measurements, or MRI or CTA to be larger than −3, the surgeon's bias should be that a transanular patch is probably unnecessary ( Fig. 38-24 ); when it is −3 or smaller, a patch is probably required. The surgeon's bias should also be that even with a transanular patch, when the z value of the “anulus” is less than −7 (<10% of cases), postrepair ratio of peak pressure in the RV to that in the LV (P _RV/LV ) may be 1 or higher, even with a properly placed transanular patch ( Fig. 38-25 ). It can be inferred from the findings outlined in Fig. 38-24 that the extremely small pulmonary valve “anulus” may in some cases be associated with diffuse hypoplasia of the distal pulmonary arteries. Thus, when a very small “anulus” is noted, preoperative evaluation of the distal pulmonary vasculature and Rp should be undertaken. If distal hypoplasia, elevated Rp, or both are observed, a reparative operation should avoided (at least temporarily) in favor of a shunt procedure. It must be emphasized that the z value is used only as a guideline. The pulmonary valve cusp configuration—number, thickness, and fusion—will influence the eventual gradient across the RV outflow tract after repair, and because of these variables, different gradients may result despite similar z values. Thus, the actual gradient should always be assessed after separation from cardiopulmonary bypass (CPB), at a minimum by intraoperative echocardiography, and preferably by direct pressure measurement.

Right Coronary Artery Branches

As a general principle, visible-to-the-eye RV coronary artery branches should be preserved whenever possible. Occasionally visible branches must be transected to achieve acceptable RV outflow obstruction relief. Before transecting a branch, its course should be fully examined. Those that traverse the body of the RV, and even those smaller branches that supply muscle farther down on the RV infundibulum than the lower margin of the infundibular incision, should be preserved. When necessary, small transverse infundibular branches, with distal perfusion that stays above the lower margin of the infundibular incision, can be sacrificed.

Anomalous Left Anterior Descending Coronary Artery

When an anomalous LAD arises from the RCA, modifying RV outflow tract management is often, but not always, necessary. Key factors are the exact course of the coronary artery and morphology of the infundibulum. In cases with a LAD that crosses high in the infundibulum near the valve anulus, and with low infundibular obstruction and a well-developed distal infundibular chamber, the obstruction can be addressed without endangering the coronary artery. On the other hand, when severe diffuse infundibular hypoplasia is present and the obstruction can be addressed only by placing a conduit from the RV to the pulmonary trunk, the RV-conduit anastomosis should be placed proximal to the coronary vessel. Occasionally the anomalous LAD is intramyocardial. This should be suspected when the left aortic sinus gives rise to an isolated circumflex coronary artery.

Pulmonary Valve

The pulmonary valve cusps should be assessed carefully, especially when a transanular patch is necessary. There is a high likelihood of bicuspid valve when a transanular patch is needed (small anulus). Orientation of the two commissures may be directly anterior and posterior, directly left and right, or any position in between. With the exception of the direct lateral orientation, the transanular incision can be designed to cross the anulus precisely through the most anterior commissure, thereby preserving the function of both cusps. This maneuver minimizes the severity of pulmonary regurgitation that results from the transanular patching.

Atrial Septal Communications

Managing the atrial septum can be essential to repair, particularly in neonates and infants. The combination of a transanular patch and high Rp can lead to postoperative RV failure. If the foramen ovale is patent under these conditions, it should be left patent. If the PFO has naturally closed, it can be reopened using a blunt instrument in most young infants. If a true atrial septal defect is present, it should be subtotally closed using a patch, leaving a small open flap that overlaps the edge of the limbus, to function like a PFO. The resulting cyanosis of atrial right to left shunting is well tolerated postoperatively, because chronic cyanosis is typically present preoperatively. In patients who do not receive a transanular patch, the atrial septum can typically be completely closed.

Tricuspid Valve

Careful attention to the tricuspid valve during VSD closure is essential, particularly in small infants. Tethering of the septal leaflet and distortion of chordal structures during VSD closure is sometimes inevitable. Valve competency should be tested routinely after VSD closure. If regurgitation is present, tricuspid valve repair should be performed. Partial closure of the anterior septal leaflet commissure is effective in restoring tricuspid valve competency when septal leaflet tethering is present. A competent tricuspid valve is critical to achieving excellent outcome, especially if a transanular patch is used.

Right Ventricular Muscle Bundles

Surgical myotomy or myectomy to manage obstructing septal, parietal, and free-wall muscle bundles in the infundibulum can have both short- and long-term implications for RV function. Despite its necessity, it remains one of the most destructive procedures in all of pediatric cardiac surgery. A minimalist approach is recommended in most cases. In neonates and infants, in whom fibrosis and excessive hypertrophy are not yet present, incision of obstructing septal and/or parietal bands without excision is all that is necessary. In many cases, if these muscle bundles are not obstructive, patching of the longitudinal infundibular incision is all that is needed to relieve infundibular obstruction. In older patients, when important fibrosis, hypertrophy, or both are present, simple incision may not relieve the obstruction, and excision may be required.

Technical Details of Repair

Immediately after CPB is established, all surgically created shunts are ligated or divided, and the ductus (if present) ligated and divided if this has not been accomplished prior to establishing CPB. Thereafter, once the heart is arrested, the right ventriculotomy or right atriotomy is made and the internal anatomy further visualized and conceptualized. The plan is to:

• ▪

  Dissect and resect the infundibular stenosis (recalling that this may be at several levels).

• ▪

  Visualize the pulmonary valve and open it if necessary.

• ▪

  Estimate dimensions of the outflow tract, valve, and anulus with a Hegar dilator, and decide whether a transanular patch is needed.

• ▪

  Repair the VSD.

• ▪

  Evaluate the atrial septum and make a decision about closing any defects or leaving a PFO.

• ▪

  Evaluate residual RV outflow tract obstruction following separation from CPB.

Repair is similar whether an RV or right atrial approach is chosen and is represented in Figs. 38-26 through 38-29 , which should be studied in parallel with this text to obtain the most complete understanding of the pathologic anatomy and its repair.

Infundibular Dissection

In patients presenting for surgery beyond early infancy, considerable RV infundibular muscle hypertrophy and fibrosis are typical, requiring a number of maneuvers during the infundibular dissection. The parietal extension of the infundibular septum is dissected away from the RV free wall and ventriculoinfundibular fold and is divided transversely 5 mm or so to the right of the attachment of the right coronary cusp of the aortic valve to the undersurface of the infundibular septum. This increases diameter of the infundibulum at its rightward end and improves exposure of the VSD from the RV approach. Any obstructive trabeculae along the left side of the outflow tract are also incised and partially removed. The aim is to increase the circumference of the infundibulum by enlarging each lateral recess in front of the infundibular septum. An obstruction at a low level (coronal plane) is relieved by dividing anomalous trabeculae above the moderator band while protecting adjacent papillary muscles; the moderator band is divided only when necessary to relieve the obstruction. When an os infundibulum is present at the level of the inferior edge of the infundibular septum, the fibrous thickening all around the ostial orifice is excised, as is any fibrous obstruction extending upstream toward the pulmonary valve. If the infundibular resection is performed using an RV infundibular incision, the incision is closed with a patch of glutaraldehyde-treated autologous pericardium or other material (see “ Decision and Technique for Transanular Patching ” later in this section). Direct closure could narrow the outflow tract. When a transanular patch is needed, a glutaraldehyde-treated or untreated pericardial patch is inserted after extending the infundibular incision across the pulmonary “anulus.”

This type of anatomic dissection is not possible in the presence of diffuse RV outflow hypoplasia and is often not possible when there is combined infundibular, valvar, and anular stenosis. These structures are all hypoplastic, a situation frequently encountered in patients who have become importantly symptomatic, as neonates or infants, and patch graft enlargement is often all that can be accomplished. In any event, particularly in infants, resection or even transection of RV muscle bundles that are not obstructive must be avoided because this unnecessarily impairs RV function.

Pulmonary Valvotomy

If pulmonary valvotomy is needed, a vertical incision is made in the pulmonary trunk, taking care to avoid damaging the valve commissures ( Fig. 38-30 ). The pulmonary arteriotomy is not made through a commissure between the cusps, because placing a patch in such an incision renders the valve regurgitant. Rarely can an adequate valvotomy be performed by simply dividing one or more sites of commissural fusion, because fusion is present in only 20% of stenotic valves and is almost always associated with important cusp thickening, particularly at the cusp free edge (see Morphology earlier in this section). After valvotomy, therefore, the surgeon may elect to excise the thickened cusp edge to relieve the stenosis, although some pulmonary valve regurgitation results. When there is cusp tethering only, the most common situation, the cusp edge may be cut from its attachment to the pulmonary artery wall over about 3 mm. This is done to one cusp at each commissure. Here, too, excising thickened cusp tissue may be required. Regurgitation from minor detachment of a cusp may be less than that from a transanular patch. If considerable cusp incision and detachment are required, regurgitation results; if there is also important residual narrowing, it is preferable to excise the cusps and place a transanular patch after completing the intraventricular part of the repair. If a transanular patch is not needed (see “ Decision and Technique for Transanular Patching ” later in this section), the pulmonary arteriotomy is closed, usually with a pericardial patch.

VSD Closure

In children and adults, the VSD is closed with a filamentous polyester or polytetrafluoroethylene (PTFE) patch; in neonates and infants, glutaraldehyde-treated pericardium works well. The patch is trimmed to be slightly larger than the VSD. Exposure may be obtained entirely with stay sutures; alternatively, the VSD is exposed through the right ventriculotomy by the assistant using two small curved retractors, one beneath both ends of the infundibular septum, which are pulled upward and apart. A third retractor is positioned in the lower margin of the ventriculotomy for gentle inferior traction. Sequencing of the suturing depends on whether the repair is from the right atrium or RV and is similar to that used for isolated VSD (see Figs. 38-26 through 38-29 ; see also Chapter 35 and Fig. 35-24, Fig. 35-25 ). For example, through the RV it is usual to begin the continuous suture at the base of the tricuspid septal leaflet at the posterior-inferior aspect of the VSD. Via the right atrial approach, the suture is often begun anterior to the insertion of the medial papillary muscle (muscle of Lancisi).

Decision and Technique for Transanular Patching

Preoperative imaging, usually by echocardiography and occasionally by cineangiography, is used to estimate the diameter of the pulmonary “anulus,” and this information is used to assess the likelihood of whether a transanular patch will be necessary. In extreme cases (of both large and small “anuli”), this measurement can be highly predictive of whether or not a transanular patch will be needed. In many less extreme cases ( z values between −2 and −4), intraoperative information will be used to decide when to place a transanular patch. The surgeon's bias regarding transanular patching is that it generally should not be necessary when the pulmonary “anulus” z value is larger than −3 as measured on the preoperative echocardiogram or cineangiogram. This is based on the high probability under these circumstances that the postrepair P _RV/LV will be less than about 0.7, and on the anticipated increased need for insertion of a pulmonary valve very late postoperatively when a transanular patch has been placed. When the patient has TF with subarterial VSD, the “Asian” variant of TF, the surgeon's bias is that there is a three in four chance a transanular patch will be necessary.

Reassessment after closing the VSD is accomplished by estimating the diameter of the “anulus” with a Hegar dilator that passes snugly but not tightly through it. This provides one more precise estimate in borderline situations. This diameter is transformed to a z value as described in Chapter 1 , Appendix Fig. 1D-1 ; generally this finding is similar to that obtained from the cineangiogram (but slightly smaller when the body surface area of the patient is less than 0.7 m ² and slightly larger in patients with a body surface area greater than about 0.7 m ² ). Generally, a transanular patch should not be placed when the z value is larger than −3. Otherwise, the incision is carried across the “anulus,” the pulmonary valve excised, and the patch inserted ( Fig. 38-31 ). If the situation is borderline, the lesser risk lies with inserting a transanular patch.

When a transanular patch is used, a major consideration is the distal extent of the incision in the pulmonary trunk, because this must be into an area of distinctly greater diameter than that of the “anulus,” which is usually the narrowest area ( Fig. 38-32 ). Otherwise, a transanular patch relieves only the small component of the high resistance produced by the length of the narrowing, and the gradient will persist essentially unchanged and be at the junction of the patch and distal pulmonary trunk. In some patients the distal pulmonary trunk is narrower than the anulus; in these cases the incision is extended into the LPA, which usually continues in the same general direction as the pulmonary trunk and is usually proportionally larger than the distal pulmonary trunk. If the origin of the LPA is proportionally no larger than the distal pulmonary trunk, the incision and patch reconstruction should be carried into the midportion of the LPA, which is nearly always wider than the origin. Care must be taken to not damage the left phrenic nerve or left superior pulmonary vein. In neonates with a patent ductus, especially if they are on PGE ₁ , it is difficult to assess the proximal LPA, and patching that extends beyond the ductus onto the distal LPA should be performed.

The transanular patch may be of glutaraldehyde-treated or untreated autologous pericardium, processed bovine pericardium, or cut from a cylinder of preclotted double-velour woven polyester, collagen-impregnated knitted polyester, or PTFE. In neonates and young infants, autologous pericardium should be used exclusively. In older patients, collagen-impregnated polyester provides the benefit of precise sizing of the patch (an important consideration ), and when properly trimmed, its convexity is ensured, as is a relatively “square cut” of its distal end (see Fig. 38-31, B ). Glutaraldehyde-treated pericardium has similar advantages. When a polyester tube is used, one is selected whose diameter corresponds to a z value of 0 to +2. Too large a transanular patch increases postoperative pulmonary regurgitation.

When the time comes for inserting the patch and the distal end of the incision is on the pulmonary trunk, the polyester tube is stretched slightly and cut to the length of the incision, cutting both ends squarely (see Fig. 38-31 ). The corrugated (crimped) nature of the tube provides sufficient length that it is convex longitudinally; the curve makes it a convex “roof” transversely. The tube is then cut longitudinally so that about three fifths of the circumference remains as the roof. Only the corners are trimmed at the distal end, leaving it very broad, while the proximal (RV) end is tapered. It is then sewn into place with a continuous 5-0 polypropylene suture (see Fig. 38-31, B ).

When the incision has been carried onto the LPA, a slightly different technique is used, in the belief that the result is more apt to be geometrically correct. For this, a rectangular piece of pericardium is cut about 1.5 times wider than the apparent diameter of the LPA and about 1.5 times longer than the incision in the LPA. It is sewn into place with continuous 6-0 polypropylene sutures placed slightly farther apart in the patch than in the wall of the LPA. A polyester tube is used for the remainder of the reconstruction ( Fig. 38-33 ). Alternatively, glutaraldehyde-treated pericardium can be used for both the transanular patch and the extension onto the LPA. Its length can be determined by measuring length of the incision from the RV to the pulmonary artery, and its maximum width is determined visually by holding the edges of the incision open at valve level and judging the size of the roof required to create a new pulmonary “anulus” whose diameter is no larger than three fourths the diameter of the ascending aorta. Alternatively, in infants, an 8-, 9-, or 10-mm Hegar dilator can be placed through the divided “anulus” and the width of the patch required to complete the roof over it measured. Both ends are cut almost transversely to create a blunt patch, particularly distally, and the patch is positioned using continuous 6-0 or 7-0 polypropylene sutures commencing at the distal end of the incision. The suture is placed using a running over-and-over technique, placing the first two or three throws along each side before pulling the pericardial patch into position as the suture is tightened. Suturing is continued down each side to anulus level, then the remainder of the right ventriculotomy is closed by incorporating the pericardial patch into it with continuous sutures. Deep bites of muscle are taken down each side and at the angle.

A monocusp may be attached to the pericardial roofing patch. The cusp diameter is fashioned somewhat larger than the planned roofed RV outflow. It is cut more or less circular and sutured to the patch when the latter suturing from distally reaches the valve “anulus.”

Assessing Postrepair Right Ventricular Outflow Tract Obstruction

Measuring Postrepair (Operating Room [OR]) P _RV/LV

In older infants and beyond, the P _RV/LV is helpful in assessing important residual RV outflow tract obstruction. After repair and separation from CPB, and preferably with the cannulae for CPB still in place, postrepair (OR) P _RV/LV is obtained. The peripheral systemic systolic blood pressure can be used to estimate the P _LV . A polyvinyl catheter is placed through the right atrial wall and passed across the tricuspid valve into the RV to measure P _RV .

If a transanular patch has not been placed and postrepair (OR) P _RV/LV is greater than 0.7, CPB should be reestablished and a transanular patch placed.

When a transanular patch has been placed and the ratio is greater than about 0.8, localizing the site of the gradient is vigorously pursued by pressure manometry or transesophageal echocardiography. If pressure gradient or localized obstruction is identified between the sinus portion of the RV and distal end of the patch, CPB is reestablished and the situation corrected. If the operation has been properly performed (in which case the gradient is located at the distal end of the patch) and if the patch has been extended into a widened portion of the pulmonary trunk or LPA, little more can be done to relieve the obstruction.

If no correctable cause of the elevation of postrepair (OR) P _RV/LV is found, and if the elevation is not extreme and the patient's condition is good, the patient should be sent to the intensive care unit (ICU) with continuous monitoring of RV pressure. There, over a few hours, postrepair (ICU) P _RV/LV may fall to reasonable levels (see Special Features of Postoperative Care later in this section). If the patient's condition in the operating room is not good or if right atrial pressure is considerably elevated above left, then the situation is precarious, although uncommon, and requires action. CPB is reestablished, and a large hole is cut in the VSD patch, usually during a brief period of aortic clamping and through a right atriotomy.

Measuring Postrepair (OR) Right Ventricular Outflow Tract Pressure Gradient

In neonates and young infants, compared with older patients, the P _RV/LV is less helpful for assessing important residual RV outflow tract obstruction. There are several reasons for this. First, the data used to develop and interpret the ratio are from older patients, so the ratio thresholds predicting poor outcomes have not been validated in neonates. Second, and most important, the physiology in neonates and young infants is substantially different from that in older patients. Especially in the operating room post-CPB, systemic vascular resistance can be quite low, yielding systolic systemic arterial pressure (and thus the P _LV ) as low as 50 mmHg. Also, Rp tends to be higher, so typically the P _RV may be as high as 40 to 45 mmHg without RV outflow tract obstruction. As a result, the P _RV/LV may approach 1.0 without any residual RV outflow tract obstruction.

Nevertheless, assessment of residual obstruction, both when the pulmonary “anulus” is left intact and when a transanular patch is used, should be routinely performed. A polyvinyl catheter is placed in the RV as described in the previous section, to measure P _RV . Another catheter is placed in the pulmonary trunk and can be manipulated into the RPA and LPA, to obtain P _PT , P _RPA , and P _LPA . In a patient with an intact pulmonary valve “anulus,” a gradient of 20 mmHg or more at the valve is an indication for revision with a transanular patch. In a patient with a transanular patch, a gradient of similar magnitude is an indication for revision at the specific site of the residual obstruction.

Management of Atrial Septum

During repair, a PFO (present in about two thirds of patients ) should generally be closed in older infants and children. Rarely, a persistent atrial communication can be the source of paradoxical cerebral emboli late postoperatively. If a true atrial septal defect is not closed, there may be left-to-right shunting at atrial level. In neonates and infants, if a transanular patch is placed or if important pulmonary regurgitation is present, a PFO is left unclosed to allow decompression of any right atrial hypertension caused by acute RV failure. Some arterial desaturation may be present in the first few postoperative days, but it then disappears as the RV remodels to accommodate the physiology of a high-volume, low-pressure circulation, as opposed to the preoperative physiology of a low-volume, high-pressure circulation. In fact, evidence of arterial desaturation is essentially proof that important RV failure is present. A PFO should be narrowed to a diameter of 3 to 4 mm. This is accomplished by suturing a portion of the free edge of the septum primum to the left side of the limbus (where it would naturally attach if spontaneous closure had occurred) using several 5-0 polypropylene mattress sutures ( Fig. 38-34 ). This will preserve a functioning, but somewhat smaller, PFO. If the pulmonary valve is competent in neonates and infants after repair, important RV failure is unlikely, and the PFO can be closed at repair.

Repair of Uncomplicated Tetralogy of Fallot with Pulmonary Stenosis via Right Ventricle

After usual intraoperative preparations (see “Preparation for Cardiopulmonary Bypass” in Section III of Chapter 2 ), a median sternotomy is performed. Prompt control of major bleeding from collaterals is accomplished with electrocautery. The usual dissections are made (see “ General Plan and Details of Repair Common to All Approaches ” earlier in this section) and purse-string sutures and tapes placed. A polyester tube (see “ Decision and Technique for Transanular Patching ” earlier in this section) may be selected and pericardium may be removed and treated with glutaraldehyde.

CPB is established, and the patient's core temperature is cooled to 24° to 32°C using direct or indirect vena caval cannulation (see “Preparation for Cardiopulmonary Bypass in Section III of Chapter 2 ). The colder end of the spectrum should be considered in older, very cyanotic patients who may have developed substantial acquired systemic to pulmonary artery collaterals. Two venous cannulae are preferred; however, a single right atrial cannula can be used (see “One versus Two Venous Cannulae” under Special Situations and Controversies in Section III of Chapter 2 ). The cardioplegic catheter (or needle) is secured into the ascending aorta. An efficient system for venting the left heart is essential for precise repair of TF, because of the potential for high collateral flow return to the left atrium. The left atrial suction line may be inserted through the base of the right superior pulmonary vein through a purse-string suture and advanced across the mitral valve to vent the LV. The aorta is clamped and cold cardioplegic solution injected (see “Cold Cardioplegia, Controlled Aortic Root Reperfusion, and [When Needed] Warm Cardioplegic Induction” in Chapter 3 ). Efflux from the coronary sinus is aspirated and discarded or allowed to escape from the right atrium.

The RV is opened through a vertical (longitudinal) incision, sparing large conal and anterior branches of the RCA that cross the RV. If it is expected that the pulmonary valve will be adequate, the incision is made in the midportion of the RV infundibulum and extended nearly to, but not into, the pulmonary valve superiorly and just into the sinus portion of the RV (see Fig. 41-27, A ). Two pledgeted stay sutures placed through each side of the incision are placed on traction for exposure (see Fig. 41-27, B ) . Alternatively, this can be achieved manually using a hand-held retractor.

Infundibular dissection is performed (see “ General Plan and Details of Repair Common to All Approaches ” earlier in this section and Figs. 38-26 and 38-27, A to C ). The pulmonary valve is examined, and if it is stenotic, a valvotomy is performed through a pulmonary arteriotomy (see Fig. 38-30, A ). Diameter of the valve anulus is estimated with Hegar dilators. If a transanular patch is considered necessary (see “ Decision and Technique for Transanular Patching ” earlier in this section), the infundibular incision is carried across the “anulus” before performing the infundibular dissection, paying attention to the position of the pulmonary valve commissures (see Fig. 38-31 ).

After the RV outflow tract is addressed, the VSD is closed using a patch (see Fig. 38-27, D to F ) . If the decision earlier in the operation has been not to use a transanular patch, measurements with Hegar dilators are repeated from the RV after VSD closure. If no further narrowing has resulted, the pulmonary arteriotomy and infundibular incision are closed with patches (see Fig. 38-30, B ). Similarly, if a transanular incision has been used, it is closed with a patch of appropriate diameter (see “ Decision and Technique for Transanular Patching ” under Technical Details of Repair earlier in this section). The right atrium is opened and the atrial septum examined. If an atrial septal defect or PFO is present, it is managed as described in “ Management of the Atrial Septum ” under Technical Details of Repair earlier in this section). The right atriotomy is closed.

Rewarming and myocardial reperfusion (see Chapter 3 ) can be commenced at any point after VSD closure. Thus, by preference, the RV outflow tract patches can be placed and atrial septum addressed either with the aortic clamp in place or with rewarming and myocardial reperfusion initiated. Separation from CPB is performed in the usual way (see “Completing Cardiopulmonary Bypass” in Section III of Chapter 2 ).

Repair of Uncomplicated Tetralogy of Fallot with Pulmonary Stenosis via Right Atrium

This procedure is identical to repair through the RV up to the point that CPB is established. Aortic cannulation is standard. Bicaval venous cannulation is required. After commencing CPB, cooling is initiated. The left side is vented by placing a cannula through the right upper pulmonary vein across the mitral valve into the LV. Once the desired core temperature is achieved, the aorta is clamped and cardioplegia administered. The caval tapes are snugged, and a long right atriotomy is carried from the base of the appendage well inferiorly, a little anterior to the inferior vena cava cannula site. The right atrium, atrial septum, tricuspid valve, VSD, and RV outflow tract are examined (see Fig. 38-29, A ).

With properly placed 6-0 polypropylene traction sutures on the septal and anterior leaflets of the tricuspid valve, edges of the VSD can usually be visualized, ¹ although with more difficulty in TF than in isolated VSD because of the leftward and anterior displacement of the infundibular septum and its parietal extension. Alternatively, manual retraction by the surgical assistant using delicate instruments can achieve similar, or superior, exposure. The pathway from sinus to outflow portion of the RV is examined. The obstructive nature of the prominent parietal extension of the infundibular septum (see Figs. 38-28 and 38-29, B ) is particularly well appreciated from this approach, and the infundibular chamber, if present, is easily visualized. The pulmonary valve can usually also be well seen. The VSD is repaired by sewing into place a patch (autologous glutaraldehyde pericardium or polyester velour) with continuous polypropylene ( Fig. 38-29, B to D ). It is closed before mobilizing and resecting the parietal band (as illustrated in Fig. 38-29 ). Often this allows better visualization of the borders of the VSD and, importantly, defines the limit of parietal extension to be resected (see Fig. 38-29, B ). The VSD patch protects the aortic valve and crista during subsequent relief of outflow stenosis. Care should be taken not to cut or loosen the continuous patch suture anteriorly when resecting the parietal band. If needed, several interrupted sutures should be placed on this portion of the rim of the VSD patch.

1 In about 5% of patients, aortic dextroposition is sufficiently severe that the cephalad (superior) borders of the VSD cannot be seen except with extreme traction on the tricuspid valve. In these cases, rather than using such strong traction, the right atrial approach is aborted and the RV approach used.

RV outflow tract obstruction is addressed following VSD closure. The parietal extension is deeply incised 2 to 4 mm beyond its origin (toward the free wall) from the infundibular septum and 4 to 5 mm above the aortic cusps, which are visualized as the cut is made (see Fig. 38-29, E ). The parietal extension is then dissected away from the ventriculoinfundibular fold (inner curvature of the RV) and from the anterior free wall of the RV and excised. The free wall of the RV is palpated occasionally from outside during this dissection to avoid perforating it. Any hypertrophied and obstructive trabeculae along the left side of the outflow tract are incised and removed together with the fibrous margins of the infundibulum. The infundibular chamber and areas just proximal to the pulmonary valve are examined to determine (in concert with the preoperative imaging studies) whether they need to be widened by an infundibular patch. Generally speaking, if this is the case, the atrial approach should not have been considered. This is because in TF, the VSD is always easier to expose and close through a ventriculotomy than through an atriotomy. Thus, if a ventriculotomy (infundibulotomy) is required because of a narrow infundibulum, the VSD should be closed through the infundibular incision. It makes little sense to close the VSD through the right atrium if an infundibular incision is required. The pulmonary valve is examined and the diameter of the “anulus” is estimated by passing a Hegar dilator antegrade across the RV outflow tract.

If a pulmonary valvotomy is needed, it is usually done through a vertical incision in the pulmonary trunk (see Fig. 38-30 ). After valvotomy, RV outflow diameter is again estimated by sizing the pulmonary valve orifice with Hegar dilators. The pulmonary arteriotomy is closed, usually with a pericardial patch. Management of an atrial septal defect or PFO and the remainder of the operation proceed as described for repair through the RV.

Repair of Tetralogy of Fallot in Infancy

A median sternotomy is performed and the heart exposed. A subtotal thymectomy is performed, paying careful attention to the phrenic nerve. If the echocardiogram or cineangiogram indicates that a transanular patch is required, and in borderline cases, the front of the pericardium is removed from where it joins the diaphragm to its most superior reflection from the aorta. This secures a piece of pericardium at least 6 cm long and 3 cm wide, tapering at both ends. The pericardium is stretched with its epicardial surface downward onto moist gauze or cardboard and is set aside for later use. Dissection of the pulmonary trunk, RPA, LPA, and ductus arteriosus or ligamentum arteriosum is easily and rapidly achieved.

CPB is established using aortic cannulation and, preferably, bicaval cannulation; however, single venous cannulation of the right atrium can be used. Standard continuous CPB with cooling to 28° to 32°C and cardioplegic cardiac arrest is preferred. The left heart is vented in standard fashion through the right upper pulmonary vein. Alternatively, hypothermic circulatory arrest can be used and is preferred by some. The ductus arteriosus, if present, is doubly ligated using two 5-0 polypropylene sutures and divided. The suture used to ligate the pulmonary artery end of the ductus should be placed precisely, at least 3 mm distal to the pulmonary artery origin of the ductus, to avoid constriction of the LPA branch or obstruction of the LPA lumen by extrusion of bulky ductal tissue. If a ligamentum is present, it should also be ligated and divided to avoid tethering of the LPA origin, which can cause late kinking and LPA obstruction, especially if pulmonary regurgitation and RV outflow tract dilatation develop. When imaging studies indicate that a transanular patch is not required and when dissection of the pulmonary trunk confirms that it is of adequate diameter, a vertical incision is made into the RV (see Fig. 38-27 ). The infundibular stenosis is completely relieved. This often involves simple transection of the parietal and septal extensions of the TSM, rather than resection (similar to that shown in Fig. 38-33, B ). The pulmonary valve is examined from below and any stenosis relieved in the manner already described. The VSD is closed through the infundibular incision (similar to that shown in Fig. 38-27 ).

The tricuspid valve is retracted and the atrial septum exposed, looking retrograde from the RV into the right atrium. If a PFO is present, it is often possible to close or modify it from this approach; if not, the right atrium is opened and the PFO is managed through this approach. Or, if there is a more extensive atrial septal defect, the right atrium is opened and the defect closed using a pericardial patch with continuous polypropylene suture. If it has to be reduced in size, it is managed as described in Fig. 38-34 . The right atrium is closed. The ventriculotomy is then closed with a narrow patch, also using a continuous suture.

When a transanular patch is indicated, the incision is carried across the “anulus” and out along the pulmonary trunk almost to the origin of the LPA, and a transanular pericardial patch is placed after VSD closure (see Fig. 38-33, A ). Should there be LPA origin stenosis, the incision passes beyond this to reach the normal-diameter LPA ( Fig. 38-35 ). If a transanular patch is used in neonates and young infants, the PFO should always be left open.

Repair of Tetralogy of Fallot with Stenosis at Origin of Left Pulmonary Artery

In this situation, there is usually sufficient hypoplasia of the pulmonary anulus and trunk that a transanular patch is also required (see Morphology earlier in this section). Repair is usually accomplished in exactly the manner described for situations in which the incision for placing a transanular patch must be extended onto the LPA (see “ Decision and Technique for Transanular Patching ” earlier in this section and see Fig. 38-35 ). In those uncommon instances in which a transanular patch is not needed, an incision is made across the stenosis in the origin of the LPA. A rectangular patch of pericardium is trimmed and sewn into place as described.

When there is virtual or total occlusion of the LPA origin, patch graft enlargement is not satisfactory. Instead, after locating the patent portion of the LPA beyond the zone of occlusion by dissecting along the chord of tissue that still connects it to the pulmonary trunk bifurcation, the patent LPA is opened longitudinally on its anterior surface for a short distance. The opened end is then sutured to the adjacent leftward edge of the pulmonary trunk with a running fine polypropylene suture to create a new posterior wall. The anterior wall is next created by a pericardial patch positioned as for reconstruction of a zone of stenosis (see earlier text). When the LPA is totally disconnected from the pulmonary trunk or is too small for this reconstruction, repair entails locating the LPA close to or adjacent to the lung hilum (usually by intrapleural dissection) and disconnecting it from any vessel, usually the ductus arteriosus, that supplies it. It is then usually possible to anastomose the LPA end to side to the leftward edge of the distal pulmonary trunk (mobilizing the trunk completely so that it will swing more easily to the left). If the LPA is narrowed proximally, however, a technique similar to that described earlier is employed.

Repair of Tetralogy of Fallot with Stenosis at Origin of Right Pulmonary Artery

This situation occurs uncommonly without associated LPA stenosis. In contrast to the LPA, the RPA is usually not an extension of the pulmonary trunk but comes off its side at a right angle. This makes the simple type of repair used for origin stenosis of the LPA less satisfactory, although it can be used when stenosis is not too severe.

Operation proceeds as usual until the VSD has been repaired. Then a small longitudinal incision is made in the pulmonary trunk to visualize the RPA orifice ( Fig. 38-36, A ). The origin of the RPA is excised from the pulmonary trunk. Lateral incisions are made to enlarge the orifice in the side of the pulmonary trunk ( Fig. 38-36, B ). The RPA is incised from its narrow orifice back into its wide portion. A rectangular piece of pericardium is trimmed and sewn to the RPA to make a markedly enlarged proximal RPA ( Fig. 38-36, C ). The proximal end of the reconstructed RPA is then sutured to the enlarged orifice in the side of the pulmonary trunk using continuous 6-0 or 7-0 polypropylene sutures, while taking care to avoid any purse-string effect ( Fig. 38-36, D ). Alternatively, the posterior edge of the opened RPA is sutured to the back wall of the opened pulmonary trunk; the rectangular piece of pericardium is then sewn to the remaining opening to widen it further.

Transection of the ascending aorta to improve exposure is rarely necessary.

Repair of Tetralogy of Fallot with Bifurcation Stenosis of Pulmonary Trunk

This condition requires appropriate reconstruction based on proper understanding of the morphology, although few papers discuss details of this repair. Both the LPA and RPA ostia are usually stenosed to a similar degree and over a short distance (<15 mm), and the distal pulmonary trunk is often similarly narrowed. The pulmonary trunk may be short, making the bifurcation proximal and more Y-shaped than usual.

In patients 5 years of age or older, the optimal procedure may be to replace the pulmonary valve, trunk, bifurcation, and proximal RPA and LPA with a pulmonary allograft ( Fig. 38-37 ). It is a less desirable operation in infants, however, because the allograft will almost certainly be outgrown and require earlier replacement than when used in older children. However, this procedure has the greatest probability of providing a good hemodynamic result in this complex situation.

Alternatively, and especially in infants, repair rather than replacement is indicated ( Fig. 38-38 ). Complete mobilization of the aorta, pulmonary trunk, RPA, and LPA is required, preferably before CPB. The vertical ventriculotomy is carried across the anulus into the pulmonary trunk and extended to the bifurcation. A second incision is made on the anterior aspect of the branch pulmonary arteries, extending from the normal diameter of the distal LPA, across the stenotic region of the LPA, onto the RPA, and extending across the stenotic region of the RPA to the distal normal-diameter RPA. Thus, the two incisions described create a T shape. Autologous pericardial tissue or allograft pulmonary artery tissue is used to patch-augment the pulmonary trunk and branch pulmonary arteries. Two patches are used, the first to patch the branch pulmonary arteries ( Fig. 38-38, A ) and the second as the transanular patch, which extends distally to the first patch ( Fig. 38-38, B ).

Repair of Tetralogy of Fallot with Anomalous Origin of Left Anterior Descending Coronary Artery from Right Coronary Artery

In hearts in which there is a large coronary artery crossing the RV outflow tract close to the pulmonary “anulus” (usually an anomalously arising LAD from the RCA, but sometimes the entire left coronary artery coming from the RCA), relief of pulmonary stenosis must neither divide nor compromise flow through this vessel. Because such a vessel is occasionally buried in muscle or fat and is not apparent on surface inspection at operation, preoperative imaging must be of sufficient quality to exclude this anomaly. When there is uncertainty, site of the usual course of the first part of the LAD is investigated during operation, and if the LAD is not there, it arises anomalously. When anomalous origin is present, technique of repair depends on morphology of the RV outflow obstruction, as usual. When the pulmonary “anulus” is of adequate diameter, either a vertical or transverse right ventriculotomy is made low in the outflow tract, well away from the coronary artery, and the infundibular stenosis is relieved from below. Alternatively, repair is accomplished via the right atrium. Any valvar stenosis is relieved via the pulmonary trunk.

When there is a small pulmonary “anulus” and proximal pulmonary trunk, a vertical ventriculotomy may be made after dissecting the anomalous artery from its bed in the RV wall over almost its entire length from its origin to near the interventricular groove. The incision is then carried beneath it and across the “anulus” into the pulmonary trunk. Infundibular stenosis is relieved in the usual fashion and a patch sufficiently large to relieve the stenosis positioned beneath the artery across the “anulus.” If this is done, care is taken to avoid making the native pulmonary valve regurgitant by injudicious valvotomy. This technique can be used only when the RV outflow tract requires mild or moderate augmentation such that the width of the patch is not so great that the coronary artery will be distorted; severely hypoplastic RV outflow tracts should not be managed in this way. Alternatively, an allograft valved conduit can be used to augment the RV outflow tract, connecting the low infundibulum to the pulmonary trunk. This technique may be used by choice, instead of the patch technique, when the infundibulum requires mild or moderate augmentation; it is the only option when marked augmentation is needed.

If the left coronary artery is damaged by the right ventriculotomy, the left internal thoracic artery can be taken down (see “Internal Thoracic Artery” under Technique of Operation in Chapter 7 ) and anastomosed to the distal left coronary artery. Alternatively, the coronary can be primarily repaired. This procedure can be life saving.

Repair of Tetralogy of Fallot after Blalock-Taussig Shunt or Polytetrafluoroethylene Interposition Shunt

Systemic-to–pulmonary artery shunts will have been created either through a thoracotomy (left or right) or a median sternotomy, and will consist of either a native systemic artery–pulmonary artery anastomosis (classic B-T shunt), or an interposition PTFE graft between the systemic and pulmonary artery. In the modern era, PTFE shunts are used much more commonly than classic B-T shunts, and a median sternotomy approach has commonly been used. However, variation in preferred shunt technique still exists, and older patients may be encountered with shunts placed using techniques rarely used today.

In many centers, median sternotomy has replaced lateral thoracotomy for primary systemic–pulmonary arterial shunts in neonates. Generally, a PTFE tube graft is used, connecting the brachiocephalic artery or brachiocephalic-subclavian junction to a pulmonary artery. In patients with a left aortic arch, the shunt is placed on the right side; with a right arch, it is on the left. At complete repair, access to the shunt is much better than that for all other types of shunts, with the graft positioned intrapericardially and centrally. Right-sided shunts are positioned medial to the superior vena cava and apposed to the lateral aspect of the ascending aorta, and on the left, just leftward of the ascending aorta. The shunt can be dissected prior to institution of CPB in most cases, the only exception being deeply cyanotic patients with a very small shunt. Interruption of the shunt is accomplished as CPB is initiated by placing appropriately sized hemostasis clips securely across the tube graft at the systemic and pulmonary ends. The graft is divided.

Median sternotomy in an older patient with TF and a classic B-T shunt is usually accompanied by profuse bleeding from arteries in front of and behind the sternum that have developed as part of the collateralization that follows subclavian artery ligation. While this bleeding is being controlled, rapid volume replacement should not be made with banked blood. This is because this low-calcium-content and low-pH blood passes directly across the VSD into the aorta and coronary arteries. If this cold, unmodified banked blood is infused rapidly, the heart may slow and even develop asystole. Warmed calcium-enriched blood may be used.

Left thoracotomy has often been used for shunt placement in neonates or small infants with a left aortic arch. Typically, a left PTFE tube graft has been used between the left subclavian artery and LPA. In part this was motivated by the ease with which it can be closed during repair. After sternotomy is performed, hemostasis secured, and sternal retractor inserted, and when the patient's condition is good, initial dissection is made. Because the graft lies deeply in the left chest, the approach is not beneath the thymus gland but over it, directly into the left pleural space. The few adhesions between the mediastinal pleura and lung are divided with the electrocautery. The PTFE tube graft is somewhat rigid and easily palpated. A small incision is made directly over it and carried down to it. At times a plane of dissection between the graft wall and surrounding tissue is easily established; if so, this dissection is carried out. Otherwise, the pericardium is opened and CPB established. The lungs are collapsed, and a plane of dissection is easily established around the graft. The shunt is clipped at each end and divided. Remainder of the operation is carried out as usual.

When a classic right B-T shunt is present in a patient with a left aortic arch, the pericardium is opened, and as the assistant elevates and retracts the ascending aorta to the left, the RPA is visualized coming from beneath the aorta. The superior vena cava is dissected off it and gently retracted rightward (in a few cases, exposure of the subclavian artery may be easier with the superior vena cava retracted to the left). Possible distortions of the RPA by the shunt are known from preoperative imaging studies, and these are kept in mind as dissection proceeds. Course of the right subclavian artery coming down to the RPA usually can be suspected from observation and palpation of a continuous thrill. The entire circumference of the subclavian artery may be freed along a short length by sharp dissection well superior to the anastomosis, and two heavy ligatures placed loosely around it. The artery is then temporarily occluded, and if vessel identification has been correct, the continuous thrill disappears, systolic and diastolic systemic arterial pressures increase, and pulse pressure narrows. If these things do not occur, the RPA has been misidentified as the subclavian artery or the shunt is small. The heart is cannulated, CPB is begun, ligatures around the subclavian artery are tied, and the operation proceeds as usual. An alternative preferred method is closure with hemostasis clips, in which case temporary ligatures are not placed.

When a classic left B-T shunt is present in a patient with a left or right aortic arch, the subclavian artery is approached from outside the pericardium. For this, the upper left pericardial stay sutures are placed on strong traction to the patient's right. Level of the LPA is noted before this maneuver; just cephalad (superior) to this level, the thymus gland and left phrenic nerve are dissected from the pericardium, sharply and over a limited area, because excessive dissection in this region can result in major bleeding that is difficult to control. A narrow retractor is slipped under the thymus, and the region of the subclavian artery is located by gentle palpation and sharp dissection beneath the thymus gland. The subclavian artery is dissected out as described for the right side, and the same tests are made for accuracy of identification. Operation then proceeds as described earlier.

If the left subclavian artery cannot be located by going over the thymus gland and phrenic nerve, an alternative method is used in patients with a right aortic arch. The brachiocephalic artery is identified beneath the brachiocephalic vein and traced distally to the point at which it bifurcates into left subclavian and left common carotid arteries. After identifying the left subclavian artery positively by the maneuvers described and by the fact that the anesthesiologist can feel the left common carotid (or left superficial temporal) pulse when the vessel is temporarily occluded, the operation proceeds as described.

Repair of Tetralogy of Fallot after Waterston and Potts Shunts

These shunts are of historical interest only; they are not used in current practice. In previous years, occasional older patients were seen for evaluation and repair who received the shunt many years before. Nearly all such patients have been repaired or have died; thus, it is rare to encounter such a patient currently. TF repair after Waterston or Potts shunt can be performed using well-described techniques, including those in editions 1 through 3 of this book.

Technique of Shunting Operations

Fig. 38-39 is a composite illustration of various positions used for systemic–pulmonary arterial shunts for augmenting pulmonary blood flow. General anesthesia with endotracheal intubation and controlled ventilation is used. Monitoring with an intraarterial catheter placed in an artery that will not serve as the systemic source of the shunt is established. Reliable intravenous access is obtained, either centrally or peripherally. Continuous pulse oxymetry is utilized. Details of each type of shunt follow.

Classic Right Blalock-Taussig Shunt

This is the original shunt described; however, it is typically not the first choice in modern practice. This is because it has the disadvantages of both sacrificing direct circulation to the right arm and delivering unpredictable flow to the pulmonary arteries. The artery can vary in size initially and can dilate over time. It may have some advantage in extremely small infants.

With the patient in left lateral decubitus position, a right lateral thoracic incision is made ( Fig. 38-40, A , inset). The thorax is entered through either the top of the bed of the nonresected fourth rib or the third interspace. A rib spreader is positioned and gradually opened (see Fig. 38-40, A ).

The first step in dissection is to securely identify the right superior pulmonary vein as it courses obliquely downward (medially and inferiorly) toward the heart to pierce the pericardium posterior to the phrenic nerve. The vein partially overlies the RPA; however, the RPA, in contrast to the vein, follows a straight course medially. With the lung retracted toward the surgeon, the periarterial sheath over the RPA is incised. Usually the superior branch of the RPA is first freed, in the process of which the main RPA (lying in a slightly different plane of dissection) can be easily overlooked. To find it, the superior surface of the right superior pulmonary vein is cleared, and it and the superior vena cava are elevated ( Fig. 38-40, A ). Dissection is carried centrally until the proximal RPA is identified as a single vessel, proximal to its first branch. With lateral traction on a loop of heavy suture placed around it, the RPA is dissected in the periarterial tissue plane as far centrally as possible. The loop is then removed so that the RPA does not inadvertently become obstructed during the next phase of the operation.

The lung is packed off and retracted inferiorly. An incision is made in the mediastinal pleura over the azygos vein and carried superiorly to the top of the chest, parallel and posterior to the phrenic nerve. The azygos vein is divided between ligatures, and the soft tissue and right paratracheal lymph nodes are divided to provide a free pathway for the turned-down right subclavian artery. Any small veins overlying it are ligated and divided. Vagus and recurrent laryngeal nerves are identified, and the periarterial plane over the right subclavian artery is incised. By grasping only the adventitia of the often delicate subclavian artery, dissection is carried distally in the periarterial plane until the origins of internal thoracic and vertebral arteries are identified. These vessels are divided between ligatures, taking care that the proximal ligature is placed 1 to 2 mm away from the subclavian artery ( Fig. 38-40, B ). Anomalies in branching of the subclavian artery are frequent. The vagus nerve is gently retracted laterally, and the periarterial plane over the subclavian artery medially is opened and dissected. The subclavian artery is divided between ligatures placed beyond the first two large branches, and a right-angled clamp is passed beneath the vagus nerve from its medial aspect superior to the recurrent laryngeal nerve ( Fig. 38-40, C ). The subclavian artery beyond the ligature is grasped with the clamp and pulled out from under the vagus nerve. Holding the artery beyond the ligature, dissection is carried centrally in the periarterial plane until the distal portion of the brachiocephalic artery and nearly the entire right common carotid artery are liberated. As dissection proceeds, a small artery is occasionally found arising from the origin of the subclavian from the brachiocephalic artery; this must be ligated and divided. The only thing limiting the turned-down length of the subclavian artery is the common carotid artery. Any obstructing bands in the paratracheal soft tissue are divided so that there is nothing in the pathway of the relocated right subclavian artery.

A light, straight arterial clamp with a handle long enough to allow easy holding by the first assistant is placed across the subclavian artery about 8 mm proximal to the point of final transection. The artery is cut squarely across, just proximal to its first branch. (Rarely the first branch comes off very proximally and the subclavian artery is unusually large beyond it. In such instances, the artery can be transected beyond this branch.) Double-looped elastic ligatures are placed around the upper branch and distal main RPA, snugged, and weighted laterally with heavy Kocher clamps. An appropriate-sized Baumgartner clamp is placed across the very proximal RPA, with the surgeon passing a right-angled clamp beneath the artery for lateral retraction as the first assistant tightens the clamp. A longitudinal incision is made in the very superior surface of the RPA (so that when the occluding devices are removed, there will be no torsion of the RPA).

Anastomosis is made with continuous or interrupted double-armed 7-0 polypropylene or polyester sutures, the continuous suture placed from within the respective arteries posteriorly ( Fig. 38-40, D ). The first assistant holds the two clamps such that the vessels are in perfect apposition and without tension during the anastomosis. Before placing the last few sutures, the lumina are examined and any tiny thrombi or debris irrigated away. After completing the anastomosis, in rather rapid succession the two doubly looped elastic ligatures are cut and removed, the clamp on the subclavian artery removed, and the proximal RPA clamp removed. Packing is placed lightly around the anastomosis, any unusual bleeding is controlled digitally, the lung is partially reexpanded, and 5 minutes are allowed to pass. During this time, a palpable continuous thrill should be present in the RPA. When the packs are removed, the field is usually dry. Rarely, an additional adventitial suture is needed.

A small chest catheter is brought out from the posterior gutter through about the seventh intercostal space and attached to gentle suction. The chest wall is closed and the lungs are well inflated before the ribs are brought together with absorbable suture. The wound is closed in layers with continuous fine polyglycolic acid sutures, and the skin approximated with a continuous subcuticular suture.

Interposition Shunt between Left Subclavian and Left Pulmonary Artery

This is a commonly performed procedure. It can be performed classically through a left thoracotomy or through a median sternotomy. The procedure performed through a thoracotomy is described.

Thoracotomy is as described for the classic B-T shunt, except on the left side. The LPA is identified and dissected out. The mediastinal pleura is opened over the left subclavian artery and contiguous portion of the aortic arch, and the periarterial sheath over these structures is opened. The subclavian artery is not mobilized.

The diameter of the graft is chosen based on the patient's weight and other factors. In normal-sized neonates or in the case of a very small LPA, a 3.5- or 4-mm PTFE tube graft is used, despite a possible small reduction in patency (see “Size” under Special Situations and Controversies, Systemic–Pulmonary Arterial Shunt, in Section II of Chapter 41 for discussion of criteria for selecting size of the PTFE tube graft). Before any occluding devices are placed, the proper length of the tube graft is determined. For this, the lung is partially inflated to bring the LPA into its usual position. When the anastomosis is completed, the graft should lie without tension and without redundancy (and thus potential kinking) between the proximal half of the subclavian artery and the superior surface of the LPA. The end of the graft that will be anastomosed to the subclavian artery is beveled ( Fig. 38-41 ), the graft is placed in a temporary position, and the other end is cut square at the point that will make the length to the LPA correct.

A delicate side-biting clamp is placed deeply on the subclavian artery so that its handle lies inferiorly and the clamp occludes the artery both proximally and distally. A longitudinal incision is made in the excluded portion of the delicate subclavian artery, and an adventitial stay suture is placed on the anterior lip. The proximal anastomosis is made with a continuous 6-0 or 7-0 polypropylene suture. The clamp on the subclavian artery is not loosened or removed at this time (see variation in detail under “Systemic–Pulmonary Arterial Shunt” under Technique of Operation in Section II of Chapter 41 ). Elastic ligatures are looped twice around the upper branch and main LPA and snugged, and heavy Kocher clamps are placed on each for lateral traction. A C-shaped clamp is placed very proximally on the LPA, taking care not to compromise the ductus arteriosus. A longitudinal incision is made in the superior surface of the LPA, making this a little shorter than half the circumference of the PTFE tube graft. The distal anastomosis is made with continuous 6-0 or 7-0 polypropylene suture.

In quick succession, the doubly looped ligatures are cut and removed, the clamp on the subclavian artery is opened and carefully removed from the field, and the LPA clamp is opened and removed. A light pack is placed about each anastomosis, with light digital pressure if needed. A continuous thrill should be present in the LPA. Other evidences of patency include registration of an immediate increase in oxygen saturation (pulse oximeter) and an immediate increase in systolic and diastolic blood pressure when the shunt is briefly occluded with forceps. Five minutes are allowed to pass.

Remainder of the procedure is completed as described for the classic B-T shunt.

The interposition operation as an isolated procedure in patients with left aortic arch can be performed through a right thoracotomy. The PTFE tube graft is anastomosed proximally to the junction of the right subclavian and brachiocephalic arteries, which is in the cupola of the chest. This operation is more difficult than that on the left side. In comparison with the classic B-T anastomosis, the PTFE interposition shunt is a more reliable resistor and is easier to close later.

Right-Sided Interposition Shunt Through Median Sternotomy

The preferred systemic–pulmonary arterial shunt in neonates with left aortic arch is a right PTFE interposition shunt performed through a median sternotomy ( Fig. 38-42, A ). After sternotomy, most of the thymus gland is removed. The pericardium is opened in its superior portion and stay sutures applied. The posterior pericardium is opened over the RPA between the ascending aorta and superior vena cava. A small, fine side-biting (C-shaped) clamp is used to isolate the junction between the brachiocephalic and right subclavian arteries. A longitudinal incision is made, and the end of a beveled 3.5- or 4-mm PTFE tube is anastomosed to the incision ( Fig. 38-42, B ). A small, fine side-biting clamp is placed on the RPA as it is elevated with fine forceps; the clamp isolates the full width of the RPA. The other end of the PTFE tube graft is anastomosed to this opening ( Fig. 38-42, C ). Continuous 6-0 or 7-0 polypropylene on a cutting needle is used for both anastomoses. The clamps are removed sequentially, the RPA clamp first. After hemostasis is secured, the pericardium is loosely closed. The remainder of the sternotomy is closed in the usual manner. Although this technique has been used primarily in neonates, it is applicable to infants.

In patients with a right aortic arch, a left-sided PTFE interposition shunt from the left subclavian–brachiocephalic junction to the LPA is preferred. Details of the technique are the same as described for the right-sided shunt.

Repair

Management is by the general measures described in Chapter 5 . Patients with TF have a particular tendency to increase their interstitial, pleural, and peritoneal fluids early postoperatively. Like other deeply cyanotic individuals, they probably have abnormal systemic and pulmonary capillary membranes, and this may make them particularly sensitive to the damaging effects of CPB (see “Response Variables” in Section II of Chapter 2 ). Therefore, particular care is taken lest loss of intravascular plasma to extravascular spaces produces undesirable hemoconcentration early postoperatively, and attention is given to the possible development of pleural and peritoneal fluid collections. If these develop, they should be aspirated.

Evaluation is complicated by the fact that in patients convalescing normally after repair of TF, with warm feet and good pedal pulses, arterial blood pressure tends to be as much as 10% lower than that in patients who are acyanotic preoperatively. Cardiac index is usually normal for this stage of convalescence, and tendency to hypotension is related to relatively low systemic vascular resistance. In the presence of other signs of normal convalescence, treatment of arterial blood pressure is not indicated.

The hemodynamic state is assessed continuously and management constantly reviewed to be certain of its appropriateness. Measurement of cardiac output is helpful, along with other determinants of adequacy of cardiovascular subsystem function (see “Cardiovascular Subsystem” in Section I of Chapter 5 ). An important right-to-left or left-to-right shunt must be identified, either by the indicator dilution method (see “Risk Factors for Low Cardiac Output” under Cardiovascular Subsystem in Section I of Chapter 5 ) or by 2D echocardiography with Doppler color flow interrogation. This is particularly important in neonates and infants, in whom the foramen ovale may have been left open for early postoperative decompression of the right atrium. Arterial desaturation is then the rule in the early hours after operation, and demonstrating right-to-left shunting at atrial level by echocardiography using color Doppler reassures that desaturation is not from pulmonary dysfunction ( Fig. 38-43 ). Desaturation from right-to-left shunting usually decreases within 48 hours as RV function improves.

In the absence of shunting, values of left (P la ) and right (P ra ) atrial pressures provide considerable insight into the relative function of the two ventricles. After repair of TF, these are usually similar, but one may be 2 to 4 mmHg higher than the other. Rarely, P la is 5 to 10 mmHg higher than P ra . When this occurs, a residual left-to-right shunt at ventricular or great artery level must be sought and, if found, promptly closed by reoperation. Even relatively small postoperative residual left-to-right shunts may not be well tolerated in repaired TF patients. An important reason for this is that preoperative physiology in TF is that of a volume-underloaded heart, rather than the volume-overloaded preoperative physiology of lesions that tolerate postoperative small residual left-to-right shunts quite well, such as VSDs, atrioventricular septal defects, or truncus arteriosus. If no shunt is found, elevated P la indicates LV hypoplasia or severe impairment of LV systolic or diastolic function, and an inotropic agent and afterload reduction are indicated.

Rarely, P ra is 5 to 10 mmHg higher than P la , indicating important volume or pressure overload of the RV or severe impairment of RV function. This situation is precarious and requires intense treatment, especially when postrepair P _RV/LV is greater than about 0.7 ( Fig. 38-44 ). If a transanular patch was not used, generally the patient should promptly be returned to the operating room and a patch placed. If a transanular patch is in place, as complete a repair as possible was obtained, and the patient's condition is reasonably good on only modest catecholamine support (e.g., 5 µg · kg ⁻¹ · min ⁻¹ of dopamine or dobutamine), then delay for a few hours is reasonable. If no improvement occurs, and particularly if postrepair P _RV/LV is 0.8 or greater, risk of death approaches 50% and intervention is indicated. In neonates and young infants, the P _RV/LV may not be as useful as in older patients. Anesthetized postoperative neonates may have low systemic vascular resistance and thus low systemic systolic blood pressure despite excellent cardiac output. In this setting, a relatively normal RV and pulmonary artery pressure may result in a P _RV/LV as high as 0.8 or 0.9. Under these circumstances, the absolute P _RV should be carefully evaluated. Systolic P _RV over 50 mmHg should be investigated routinely, and that between 40 and 50 mmHg considered for investigation. Regardless of the patient's age, investigation, when indicated, is the same. A right ventriculogram and determination of site of the gradient by cardiac catheterization is performed. If an appreciable gradient is found in the RV or at the pulmonary “anulus,” or a localized important uncorrected LPA or RPA origin or bifurcation stenosis is found, correction of these areas of residual stenosis at prompt reoperation is indicated.

However, if the original repair was complete, it is likely that none of these will be found. Instead, the gradient will be located at the distal transanular patch suture line. This circumstance is uncommon (1%-2% of patients), limited almost entirely to patients with severe hypoplasia of the “anulus” and pulmonary trunk. In that setting, and particularly without a distal widening (in the distal pulmonary trunk or LPA) into which the transanular patch can be extended, it may be impossible to make a geometrically proper patch. If evaluation reveals that hypoplasia or discrete stenosis is present in the branch pulmonary arteries with normal distal pulmonary arterial development, then further patch augmentation of the pulmonary arteries is indicated. If the pulmonary artery hypoplasia is diffuse, a large perforation is made in the VSD, preventing the P _RV from becoming suprasystemic, and augmenting systemic output from right-to-left shunting across the VSD.

Particular attention is paid to the possible need for reoperation for bleeding. Preoperative polycythemia and depletion of many clotting factors, extensive collateral circulation, and damaging effects of CPB often combine to produce a considerable bleeding tendency. Intense treatment, particularly with platelet-rich plasma, is indicated. The usual criteria for reoperation are followed (see “Bleeding” in Section II of Chapter 5 ), and prompt reoperation is advised as soon as they are violated. This practice was one factor contributing to the considerable reduction in risk of operation in the early 1960s. Currently, with careful intraoperative hemostasis and definitive repair at a young age, reoperation for bleeding is rarely necessary.

After the patient leaves the ICU, body weight is followed closely because transient fluid retention is common, particularly when a transanular patch has been used. Pharmacologic management of right-sided heart failure is indicated.

Systemic–Pulmonary Arterial Shunting

In neonates and young infants, careful intraoperative and postoperative monitoring and control of Pa o ₂ , pH, and buffer base are required (see “Neonates and Infants” in Section II of Chapter 5 ). The usual intense postoperative care and protocols are applied (see Chapter 5 ). An intraarterial catheter is used to monitor blood pressure, paying careful attention to the systolic/diastolic difference and absolute diastolic pressure. The patient is returned to the ICU ventilated through an endotracheal tube. A chest radiograph is obtained immediately. Ventilation is controlled postoperatively for at least several hours and up to a full day, until stable hemodynamics and confirmation of balanced systemic-pulmonary blood flow is assured. A combination of Sa o ₂ , diastolic blood pressure and pulse pressure, and various signs that reflect systemic cardiac output are used to estimate the systemic-pulmonary blood flow balance. Assuming normal hematocrit and pulmonary gas exchange, an Sa o ₂ of about 80% usually reflects well-balanced systemic and pulmonary blood flow. Diastolic blood pressure ideally should be above 30 mmHg. Major diversions from these levels usually indicate an imbalance of systemic-pulmonary blood flow. A repeat chest radiograph should be performed to confirm that a pulmonary parenchymal process, and thus gas exchange, is not responsible. If this is ruled out, intravascular volume, pharmacologic (inotropes), and ventilator manipulation should be initiated to restabilize the balance of flow.

Maintaining an adequate cardiac output and blood pressure is an important factor in assuring shunt patency in the vulnerable period of the first 48 hours after surgery. Some centers use a heparin drip as an additional measure. Additionally, or alternatively, aspirin at 10 mg · kg ⁻¹ daily may be started and continued for the life of the shunt.

Infrequently, mild renal failure, and rarely, acute renal failure and anuria, develop after a simple shunting procedure. This is related to the renal pathology sometimes present in cyanotic patients with TF and to renal damage by radiopaque dye that may have been used for the cineangiogram a few hours or days before operation. Therefore, urine flow is carefully observed postoperatively.

A surgically created shunt must function. Therefore, auscultation is used to assess its patency during the entire postoperative hospitalization. If doubt develops concerning shunt function, immediate 2D echocardiography, cineangiographic study, or both are indicated. If it is poorly functioning, prompt reoperation is indicated. In older patients with large acquired systemic-to–pulmonary artery collaterals, a continuous murmur is present preoperatively, and therefore simple auscultation is not as useful early postoperatively. In this setting, if cyanosis has not improved, echocardiography and/or cineangiography is indicated.

Survival

Early (Hospital) Death

Although hospital mortality in a few series of heterogeneous groups of patients has been 1% or less, in most series it varies between 2% and 5% ( Fig. 38-45 ). TF repair in patients 90 days of age or younger at 32 centers participating in the Society of Thoracic Surgeons congenital heart database over a 3-year period from 2002 to 2005 was associated with a mortality of 6.1% (CL 3.6%-9.6%). In the same centers, mortality for shunt palliation was 8.3% (CL 5.4%-12%).

Because the early rapidly declining phase of hazard does not flatten out until 3 to 6 months after operation ( Fig. 38-46 ), hospital or 30-day mortality underestimates the risk of death early after repair.

Time-Related Survival and the Question of “Cure”

In considering survival after surgical repair, it must be recalled that deaths occurring before repair are not represented. Thus, an institution that delays repair until some specified age may have a few patients who, whether shunted or not, die before repair, whereas an institution that has a policy of one-stage repair in all symptomatic patients, no matter how young, may have an apparently higher mortality while actually saving more lives. Vobecky of Toronto's Hospital for Sick Children examined this issue in 270 TF patients younger than age 18 months. A few deaths occurred before palliation, between palliation and repair, and after repair ( Table 38-4 ). Major noncardiac anomalies may preclude repair, and major associated malformations may increase operative risk at any age. At present, the data show nearly equal time-related survival for one-stage repair performed at any age and staged operation.

Table 38-4

Time of Death of Infants with Isolated Tetralogy of Fallot ( n = 237)

Data from Vobecky and colleagues.

Timing of Death	No.	%
None	218	92
Before palliation	3	1.3
At palliation	2	0.8
Secondary palliation	1	0.4
After palliation/before repair	8	3.4
At repair	7	3.0
After repair	1	0.4
T otal deaths	22 a	9.3

a Fourteen deaths occurred before repair (5.9%; CL 4.3%-7.9%).

In one analysis, time-related survival after repair in heterogeneous groups of patients at 1 month and 1, 5, 10, and 20 years was about 94%, 92%, 91%, 90%, and 87%, respectively ( Fig. 38-47 ). Patient-specific survivals and those of homogeneous groups of patients vary, with 10- and 20-year values as high as 97% in some circumstances ( Fig. 38-48 ). In another analysis, overall time-related survival was 80% at 40 years. In that study, predicted 40-year survival for patients repaired in the latter part of the experience (operation performed in the year 1985) was 88%.

“Is the patient cured of TF?” This is a critical question that must be examined not only for the entire heterogeneous population of patients undergoing repair but also for specific patients, taking into account the strength and time-relatedness of their various risk factors. For operation to be curative, the hazard function for death after the early postoperative period (3-6 months) must be no greater than that for an age-sex-race–matched general population and have no late increase until that imposed by older age on the general population. Hazard function for death after repair in a heterogeneous group of patients has a constant hazard phase (as opposed to a rising phase) late postoperatively, as demonstrated in the analysis of early Mayo Clinic patients included in the study of Fuster and colleagues and subsequently reported by Murphy and colleagues. At 30 years, survival for patients who left the hospital alive was 86% compared with 96% in the general population ( P < .01).

The 35-year follow-up of patients operated on by Lillehei and colleagues and the 30-year follow-up of patients operated on at Johns Hopkins Hospital are also consistent with presence of a low constant phase of hazard without a late rising phase.

Level of the constant hazard phase is about three times higher than that of a matched general population, but many patients had numerous risk factors. The hazard function for younger patients in the combined Boston Children's Hospital–UAB data set, most of whom underwent primary (one-stage) repair, is behaving as if the constant hazard phase will be closer to that of a matched general population when they have been followed long enough for this to be identified. The Boston-UAB long-term data suggest that a late rise in the hazard function will not occur within the first 20 to 30 postoperative years (see Fig. 38-46 ).

Thus, the inference is that time-related survival of most patients after repair of TF with pulmonary stenosis under proper circumstances is excellent, approaching that of the general population, but that the risk of death throughout life is slightly greater than that of the general population.

Modes of Death

Considering death with multiple subsystem failure to be basically death in subacute heart failure, only half the patients who died in hospital after repair in the combined Boston Children's Hospital–UAB study died this way. Pulmonary failure, hypermetabolic state, and catastrophic surgical or early postoperative events account for the remainder, a higher percentage than after most kinds of cardiac surgery in adults. Pathologic basis of the pulmonary failure has been described by Harms and colleagues, who found in their autopsy studies that extensive alveolar and interstitial edema and hemorrhage are characteristic of the lungs of patients dying early after repair of TF. This process is probably caused by the damaging effects of CPB (see Chapter 2 ), to which severely cyanotic and polycythemic patients seem particularly sensitive. Thus, further improvement in results of repair may demand not only improved myocardial management but also lessening of the damaging effects of CPB and improved technical proficiency in the operating room and ICU when repair is being done in very small patients.

Incremental Risk Factors for Death

Incremental risk factors for death early and late after repair have been identified from a number of studies. A typical analysis from a single institution, identifying early hazard phase and late hazard phase risks, is shown in Table 38-5 . There are a number of difficulties in definitively identifying risk factors for early death. These difficulties are that some variables were available for one analysis and not for another, that the risk factors may be different if procedural as well as patient characteristics are considered, and that some simultaneously determined “independent” risk factors are highly correlated and thus may be surrogates for one other (see “Variable Selection” in Section IV of Chapter 6 ). One of the most important difficulties is that in the current era, early mortality is so low that identifying risk factors for that phase is not possible.

Young Age at Repair

Young age at repair ² has been identified as a risk factor for death early after repair. There are, however, two important qualifications that accompany this observation. First, young age is not necessarily an immutable risk factor, because the age at which risk increases appreciably has been progressively reduced as experience and knowledge have grown. This improvement is illustrated by the UAB experience, in which risk of hospital death and predicted 20-year survival after repair in a 6-month-old infant improved considerably between 1967 and 1986 ( Fig. 38-49 ). The incremental risk of young age in general is currently unapparent until age is younger than 3 months, and in some circumstances younger than 1 month ( Fig. 38-50 ). Second, studies examining young age as a risk factor for early death have the inherent bias that only symptomatic patients were repaired in the neonatal period or early infancy. Because symptoms correlate with less favorable morphology of the RV outflow tract in patients with TF, it follows that patients who underwent repair at a very early age uniformly had less favorable morphology. Thus, there were no patients who underwent very early repair in these series with favorable morphology (asymptomatic). Even with multivariable analysis, it is difficult to overcome this bias.

2 Body surface area is a more statistically significant risk factor than young age in the majority of multivariable analyses, but most groups prefer to think in terms of age. Therefore, a regression analysis has been made of the relation of age to body surface area so that one can be used to estimate the other (see Appendix 38A ).

Reduction of the age at which risk is increased is due in part to increasing technical expertise in intracardiac surgery and early postoperative care in the very young. Further improvements in these areas may completely neutralize the increased risk of young age. Control of the damaging effects of CPB (see Chapter 2 ) and improvement in the function of the heart early postoperatively, brought about by more effective intraoperative myocardial management, will assist in this effort.