Ventricular Septal Defect

Size

VSDs are highly variable in size, and their division into size groups is arbitrary but useful. The echocardiographic criteria for VSD size are discussed in “ Two-Dimensional Echocardiography ” under Clinical Features and Diagnostic Criteria.

Large VSDs are approximately the size of the aortic orifice or larger. They offer little resistance to flow, and thus their VSD resistance index ¹ is less than 20 units · m ² in situations in which the calculation of the index is valid. Right ventricular (RV) systolic pressure approximates left ventricular (LV) pressure, and the pulmonary to systemic blood flow ratio ( ) is increased to a degree dependent on the level of pulmonary vascular resistance (Rp).

1

where BSA is body surface area, P _LV is left ventricular systolic pressure, P _RV is right ventricular systolic pressure,
is pulmonary blood flow, and
is systemic blood flow.

Moderate-sized VSDs, although still restrictive, are of sufficient size to raise RV systolic pressure to approximately half LV pressure and
to 2.0 or greater.

Small VSDs are of insufficient size to raise RV systolic pressure, and is not increased above 1.75. Small VSDs have a VSD resistance index greater than 20 units · m ² . Multiple small defects behave in aggregate as a large defect.

Location in Septum and Relationship to Conduction System

VSDs can occur in all portions of the ventricular septum ² ( Fig. 35-1 ). VSDs with entirely muscular borders (muscular VSDs) may occupy several areas of the ventricular septum; other VSDs have one or several nonmuscular borders consisting of spaces or structures against which they are juxtaposed ( Table 35-2 ). These nonmuscular borders may be a semilunar valve, an AV valve, or the crux cordis (intersection of the posterior aspect of the interventricular septum and AV junction). Some VSDs in the periphery of the ventricular septum are bordered by the ventricular free wall, but such VSDs are conventionally considered to be muscular. VSDs in the category of subarterial may be (1) juxta-aortic , (2) juxtapulmonary , (3) juxta-arterial (bordered by both pulmonary and aortic valves), or (4) juxtatruncal (bordered by the valve of a common arterial trunk). Subarterial VSDs are typically associated with some degree of overriding of the related arterial trunk, and the margin of the VSD is actually a space over which is a semilunar valve(s).

2 The location is described in words that are relevant to the RV aspect of the VSD (see “Right Ventricle” under Cardiac Chambers and Major Vessels in Chapter 1 ), because most reparative procedures are performed from that aspect.

Many VSDs are associated with malalignment of portions of the ventricular septum or atrial septum relative to the interventricular septum, in which case an AV valve usually overrides the VSD. Malalignment VSD terminology results from two-dimensional (2D) echocardiographic examination of the heart regarding alignment of the trabecular and the outlet (conal) septum. In some cardiac anomalies, the aorta seems displaced relative to the VSD. The malalignment is referred to as anterior when the outlet septum appears anterior to the trabecular septum, with the VSD interposed. Tetralogy of Fallot–type defects are considered anterior malalignment types, with the aorta “overriding” the VSD (see Fig. 35-18, C ). Malalignment is posterior when the outlet septum appears posterior to the trabecular septum in anomalies such as interrupted aortic arch and severe coarctation of the aorta. There may also be a rotational malalignment in anomalies characterized under the broad category of Taussig-Bing heart.

Anatomic location of the VSD determines its relation to the conduction system.

VSDs may also be characterized according to their commitment to the great arteries (Lev and colleagues ): subaortic, subpulmonary, doubly committed, and noncommitted. This type of characterization—which is relational, not morphologic—preferably is restricted to hearts with double outlet ventricles, because its use in other situations has resulted in considerable confusion.

All these features of the location of VSDs should be included in descriptions of these defects.

Perimembranous Ventricular Septal Defect

Approximately 80% of patients operated on for primary VSD have a perimembranous VSD. These defects could be called junctional VSDs because they are in the junctional area between the trabecular (sinus) and outlet (conal) portions of the ventricular septum ( Fig. 35-2 ) and usually appear to be between the posterior and anterior divisions of the trabecula septomarginalis (septal band). Thus, these VSDs are between the outlet (conus) and inlet (ventricular) portions of the right ventricle, but characteristically they are in the outlet portion of the left ventricle.

Perimembranous VSDs are often associated with anomalies of the outlet septum and other adjacent structures, although when small, they may be truly isolated anomalies. Some perimembranous VSDs are juxtatricuspid (abutting the tricuspid valve), juxtamitral, and juxta-aortic . These perimembranous VSDs are also conoventricular (conotruncal) ( Fig. 35-3 ). Such defects abut the commissural area between the noncoronary and right coronary cusps of the aortic valve. Others are only juxtatricuspid ( Fig. 35-4 ), and in hearts with these as well as in hearts with perimembranous VSDs, the bundle of His passes along the posteroinferior border of the defect. Some perimembranous VSDs abut none of these valvar structures and are separated from the tricuspid anulus posteriorly by a band of muscle that is part of the posterior division of the trabecula septomarginalis joining with the ventriculoinfundibular fold. The bundle of His is not in this muscular band but is in its usual position more posteriorly. Technically, although this type of defect is located in a perimembranous position, it is better classified as muscular inlet–type VSD because all borders are muscle.

VSDs have also been described in the past as typically high, infracristal, membranous, or perimembranous, without the original specific description.

As already indicated, the AV node and penetrating portion of the bundle of His are in their normal position in hearts with perimembranous VSDs. As the bundle penetrates the fibrous right trigone of the central fibrous body at the base of the noncoronary cusp of the aortic valve, it lies along the posteroinferior border of perimembranous and inlet-type VSDs. As the bundle continues along the inferior border of the VSD (at times slightly to the left or right of the free edge), the left bundle branch fascicles emerge from the branching portion. Only the right bundle branch remains when the bundle reaches the level of the muscle of Lancisi.

Abnormalities of the ventricular portion of the membranous septum are often associated with perimembranous VSDs. The membranous septum may be absent or nearly so, and then the right trigone (beneath the nadir of the noncoronary aortic valve cusp) and base of the septal and anterior leaflets of the tricuspid valve are exposed and form the posteroinferior rim of the VSD (see Fig. 35-3 ). The bundle of His, as it penetrates the fibrous right trigone at the base of the noncoronary cusp, is intimately related to the posteroinferior angle of such a defect. This is associated with a deficiency in the posterior limb of the trabecula septomarginalis. Rarely the ventricular portion of the membranous septum may be well developed, thickened, and perforated by one or many holes, forming an aneurysm of the membranous septum that bulges toward the right in systole. This so-called aneurysm is simulated on angiography by the much more common tethered anterior leaflet and the involved and usually fused chordae. Accessory fibrous tissue not part of the tricuspid valve mechanism may lie along the posterior or superior margin of the defect. This phenomenon is most marked in the flap valve VSD .

Not surprisingly, in hearts with perimembranous VSDs, still other adjacent structures may be abnormal. The medial papillary muscle characteristically joins the anteroinferior angle of the defect and receives chordae from adjacent portions of the tricuspid anterior and septal leaflets. These chordae may be increased in number and abnormally positioned around the edges of a perimembranous VSD, attached to the posterior edge, superior edge ( Fig. 35-5 ), or most often anterior edge. A thick leash of chordae joining the center of the anterior edge of a large defect may produce an appearance on angiography or even at operation of a double defect. Chordae from the anterior leaflet may attach to all three margins, and the anterior leaflet then limits the shunt from left to right through the defect, as well as hinder its repair.

Close association of some perimembranous VSDs with the commissure between anterior and septal tricuspid leaflets sometimes results in adherence of leaflet tissue to edges of the defect and shunting directly from LV into right atrium ( Fig. 35-6 ). This so-called LV–right atrial defect, which constitutes fewer than 5% of perimembranous VSDs in this region, rarely involves the AV septum. Adherence of tricuspid leaflet and chordal tissue is also an important mechanism of spontaneous closure of these VSDs.

Ventricular Septal Defect in Right Ventricular Outlet (Doubly Committed Subarterial Ventricular Septal Defect)

Some 5% to 10% of patients treated operatively have a single VSD, usually of moderate or large size, within the outlet portion of the RV. VSDs in this location are also in the outlet portion of the LV and, in contrast to perimembranous VSDs, are more beneath the right aortic cusp than the commissure between it and the noncoronary cusp. In the past, these have also been termed conal, infundibular, supracristal, and intracristal defects. The complex morphology of the ventricular septum in the outlet portion of the RV and many controversies concerning the term “outlet septum” support use of a simple descriptive terminology for this group of VSDs.

VSDs in this general location are bordered in part by a space over which lie the pulmonary and aortic valves ( Fig. 35-7 ). As such, these VSDs are subarterial. VSDs of this type are more common in Asians than in white or black races. Subarterial VSDs may be circular, diamond shaped, or oval with the long axis lying transversely ( Fig. 35-8 ). When viewed from the LV aspect, these defects are in the outflow portion of the ventricular septum (see Fig. 35-7, B ), beneath the right coronary cusp (or commissure between it and the left cusp). The aortic and pulmonary valve cusps are separated by only a thin rim of fibrous tissue. The right aortic cusp and (less often) noncoronary cusp may prolapse into the upper margin of the defect, with or without aortic regurgitation (see Section II later in this chapter).

The posteroinferior margin of RV outlet VSDs is usually well separated from the tricuspid valve anulus by a band of muscle and is consequently well above the bundle of His. Occasionally, however, a particularly large confluent VSD may be both subarterial and perimembranous ( Fig. 35-9 ). The conduction system is related to such a VSD as it is to other perimembranous defects. This particular type of VSD is sometimes associated with severe overriding of the aorta, and the cardiac anomaly is then termed double outlet right ventricle (DORV) with doubly committed VSD . The same type of VSD may also be seen in double outlet left ventricle (DOLV), in which the pulmonary artery severely overrides the VSD.

Morphology of these subarterial VSDs has been well elucidated by 2D echocardiography and color Doppler examinations. Despite the potential confusion of using Lev's relational terminology in a morphologic sense, in the echocardiographic literature, subarterial defects are usually referred to as doubly committed VSDs . Thus, it is useful to combine morphologic and echocardiographic descriptions to characterize these VSDs occurring in the RV outlet as doubly committed subarterial VSDs . Echocardiography has demonstrated that aortic and pulmonary valves are frequently at the same level in the presence of subarterial (or doubly committed) VSDs, rather than the pulmonary valve being elevated above (cephalad to) or offset relative to the aortic valve, seemingly by the RV infundibulum. This description often provides a diagnostic tool useful in both echocardiography and angiography, along with the finding that the outlet septum appears to be absent and the subpulmonary infundibulum deficient. Echocardiography has also demonstrated the frequently associated prolapse of an aortic cusp and aortic regurgitation present in up to half of patients with this type of VSD. Aortic cusp prolapse may nearly close the VSD during diastole. At times the fibrous raphe between the arterial valves is displaced relative to the ventricular septum, resulting in overriding of one arterial valve and narrowing of the other.

Some VSDs in the RV outlet are only juxta-aortic and abut the nadir of the right coronary cusp. The cusp typically prolapses through this type of VSD, and aortic regurgitation frequently develops. Rarely, VSDs in the RV outlet are only juxtapulmonary and lie far to the left.

Some defects in the outlet portion of the septum have muscular borders and lie in the substance of the infundibular septum (muscular VSD, outlet type), with a muscle bridge of infundibular septum superior to the defect. The superior muscular bridge may be malaligned and displaced leftward into the aortic outflow tract (posterior malalignment type of VSD), producing muscular subaortic stenosis that lies above the VSD. This anomaly occasionally occurs in association with interrupted aortic arch and with coarctation, although perimembranous VSDs are more common in both settings.

Inlet Septal Ventricular Septal Defect

Five percent or less of surgical patients have inlet septal VSD (or AV septal type or AV canal type of VSD). This defect involves the RV inlet septum beneath the tricuspid septal leaflet and LV outlet septum . Its posterior margin is formed by the exposed AV valve anulus (juxtatricuspid), and its anterior margin is muscular and crescentic ( Fig. 35-10 ). Superiorly, inlet septal defects usually extend to the membranous septum. The AV septum is intact, in contrast to the situation in hearts with AV canal septal defects (see Morphology in Chapter 34 ). The anterior (septal) mitral leaflet occasionally may be cleft, either partially or completely, with associated mitral regurgitation. Rarely, VSDs in the inlet portion of the septum extend completely to the crux cordis and thus are also juxtacrucial in position. The tricuspid valve is overriding and usually straddling.

In inlet septal VSDs, the AV node lies more laterally and anteriorly along the tricuspid anulus than normal and at the point at which the tricuspid anulus meets the underlying ventricular septum, because of straddling of the tricuspid valve. The bundle of His lies along the posteroinferior rim of the inlet septal VSD, slightly on the LV side, as in juxtatricuspid VSDs.

A muscular VSD can occur in the inlet portion of the ventricular septum beneath the tricuspid septal leaflet ( Fig. 35-11 ). The posterior margin of such a defect is separated from the tricuspid ring by muscle. A muscular VSD must be distinguished from the inlet septal type of VSD because the conducting tissue runs superior and anterior to a muscular defect.

Muscular Ventricular Septal Defect

VSDs in other locations are generally muscular VSDs. Such defects are frequently multiple and may be associated with perimembranous or subarterial VSDs. Single or multiple muscular defects in the trabecular septum are more common in infants requiring operative treatment than in older children.

Muscular defects can occur anywhere in the ventricular septum (see Fig. 35-1 ). Those in the middle portion of the trabecular septum are the most common ( Fig. 35-12 ) and may be overlaid by the trabecula septomarginalis; thus, even when single on the LV side, these defects have at least two openings on the RV side. Anterior muscular defects are usually multiple and most often in the apical and outlet portions of the septum. They may extend all along the anterior part of the septum from apex to outlet septum. Typically there are more openings on the RV than LV side.

A particularly important group of patients are those with Swiss cheese defects ( Fig. 35-13 ), many defects of variable size, not only along the anterior portion of the septum but throughout the midportion as well. These defects often pass obliquely through the septum to appear on both sides of the trabecula septomarginalis or in the anterior part of the septum. They may be associated with large or small perimembranous or subarterial defects. Major associated cardiac anomalies are common, especially severe coarctation of the aorta.

The bundle of His is not closely related to the borders of any muscular VSD.

Confluent Ventricular Septal Defect

Some unusually large, single confluent VSDs involve more than one area of the septum. Rarely a confluent VSD may involve most of the septum ( Fig. 35-14 ), but hearts with such defects should not be classified as having a single ventricle.

Ventricular Septal Defect with Straddling or Overriding Tricuspid Valve

In rare instances, tricuspid valve chordae may straddle the ventricular septum in association with a large inlet septal defect resembling an inlet septal–type VSD but extending to the crux cordis ( Fig. 35-15 ). The tricuspid valve usually overrides both ventricles. When overriding is severe, the tricuspid anulus is usually very large, and many chordae from it are attached to the LV side of the septum (a combination of straddling and overriding). The atrial septum is malaligned relative to the ventricular septum. The RV is often hypoplastic. The tricuspid valve may be regurgitant.

Associated Lesions

Nearly half of patients undergoing surgical treatment for a primary VSD have an associated cardiac anomaly. A moderate-sized or large patent ductus arteriosus (PDA) is present in about 6% of patients of all ages, but about 25% of infants in heart failure. VSD occurs in combination with moderate or severe coarctation of the aorta in about 5% of patients. This combination is also much more common among infants with large VSD coming to operation younger than age 3 months.

Congenital aortic stenosis occurs in about 2% of patients requiring operation for VSD. Subvalvar stenosis is more common than valvar and may also occur in association with infundibular pulmonary stenosis. Subvalvar stenosis can be due to (1) a discrete fibromuscular bar lying inferior (caudad or upstream) to the VSD; (2) a discrete fibromuscular bar located distal (downstream) to the VSD, often consisting of displacement of infundibular septal muscle into the LV outflow tract (posterior malalignment), and often associated with aortic coarctation and interrupted arch (see “Morphology” in Sections I and II of Chapter 48 ); (3) pulmonary artery banding ; and (4) excrescences of AV valvar tissue.

Congenital mitral valve disease occurs in about 2% of patients. One of the pulmonary arteries may be absent or severely stenotic. Severe peripheral pulmonary artery stenoses occur rarely.

Although atrial septal defects in general are not considered major associated anomalies, they may coexist with a large VSD in small infants and may be important lesions.

Severe positional cardiac anomalies (e.g., isolated dextrocardia, situs inversus totalis) are uncommon in patients with VSD.

Pulmonary Vascular Disease

The classic description of the pathology of hypertensive pulmonary vascular disease is that of Heath and Edwards ( Box 35-1 ).

Rp in patients with large VSD (and those with large PDA) is positively correlated with histologic severity of the hypertensive pulmonary vascular disease, classified by Heath and colleagues ( Fig. 35-16 ). A close positive correlation also exists between lowest Rp at rest or with isoproterenol infusion and Heath-Edwards grade of vascular disease. Heath-Edwards grades above 3 were not found in patients with Rp index less than 7 units · m ² , whereas those with Rp greater than 8.5 units · m ² showed changes characteristic of grade 4 or greater. Similarly, Fried and colleagues found a rather close negative correlation ( P = .001) between magnitude of left-to-right shunt and Heath-Edwards grade in infants and children coming to VSD repair. Variability in these matters is not unexpected because Heath-Edwards classification is based on the most severe lesion seen, regardless of its frequency. As noted by Wagenvoort and colleagues and Yamaki and Tezuka, grading should include assessment of the number of vessels affected. In addition, calculation of Rp is open to errors.

Hislop and colleagues provide a different view of hypertensive pulmonary vascular disease in infants with large VSD. Other investigators had noted earlier that intimal proliferation (and thus Heath-Edwards changes of grade 2 or greater) rarely develops in patients with large VSD until 1 or 2 years of age, despite infants occasionally having severely elevated Rp. Hislop and colleagues found that infants dying at 3 to 6 months of age with large VSD and high (>8 units · m ² ) Rp with intermittent right-to-left shunting have marked medial hypertrophy affecting both large and small pulmonary arteries, including those less than 200 µm in diameter. The usual number of intraacinar vessels was present. By contrast, these investigators found that infants 3 to 10 months of age with large VSDs dying with a history of large and heart failure and normal or slightly elevated Rp have medial hypertrophy affecting mainly arteries larger than 200 µm. The intraacinar vessels were fewer than usual, so-called lessened arterial density. These histologic features have been shown by Rabinovitch and colleagues to correlate with pulmonary hemodynamic findings after repair of VSDs. Fried and colleagues have emphasized that Heath-Edwards grade and arterial density are the best correlates of fall in pulmonary artery pressure after repair.

Histologic reversibility of pulmonary vascular disease after closure of VSD has not been documented. Favorable results in infants may be from an increase in arterial density as growth proceeds. Presumably, pulmonary vascular disease of Heath-Edwards grade 3 or greater severity is not reversible.

Clinical Findings

In infants, signs and symptoms of heart failure include tachypnea and liver enlargement, often associated with poor feeding and growth failure, and physical findings of a precordial pansystolic or more abbreviated systolic murmur and a hyperactive heart. These findings suggest the diagnosis of a large VSD. An apical diastolic murmur suggests large flow across the mitral valve during diastole, the result of a large . Cardiomegaly and evidence of large are seen on the chest radiograph ( Fig. 35-17 ). The electrocardiogram (ECG) usually shows biventricular hypertrophy. In older patients with large VSD, the history is often nonspecific, but examination also shows evidence of LV and RV enlargement and a systolic murmur usually best heard in the third and fourth left interspaces. In patients with doubly committed subarterial VSDs, the systolic murmur is maximal in the second and third interspaces, and in defects shunting mainly into the right atrium, in the fourth and fifth interspaces.

A high Rp from severe pulmonary vascular disease changes the hemodynamic state and clinical findings in patients with large VSDs. A large left-to-right shunt is no longer present because output resistances of the two pathways for LV emptying are similar, and the shunt is bidirectional and of about equal magnitude in both directions. The heart is not enlarged or hyperactive. A systolic murmur (produced by the large flow across the VSD) is soft or absent, and no apical diastolic murmur is heard. The pulmonary component of the second sound at the base is loud and sometimes palpable. Chest radiography reflects these features (see Fig. 35-17 ). ECG shows severe RV hypertrophy rather than combined ventricular hypertrophy, and evidence of LV volume overload. When pulmonary vascular disease is even more advanced, cyanosis develops (Eisenmenger complex) because the shunt across the VSD becomes right to left as RV output resistance through the pulmonary vascular bed becomes higher than that through the VSD and aorta.

Patients with small VSDs have small shunts and often no abnormal signs or symptoms other than a pansystolic murmur. Chest radiography and ECG both may be normal. When the defect is moderate in size, the LV is mildly or moderately enlarged (shown by physical examination, chest radiography, and ECG), and the volume of the RV is increased.

When there is associated pulmonary or aortic stenosis, diagnostic features are changed. Thus, with important pulmonary stenosis, is reduced, and the shunt may even be right to left. RV hypertrophy is increased. With important aortic stenosis, the load on the LV is increased, and if the obstruction is cephalad to the VSD, left-to-right shunt is also greater, resulting in more than the expected degree of LV hypertrophy on ECG. Coarctation of the aorta may also produce these features in older children.

Two-Dimensional Echocardiography

Two-dimensional echocardiography imaging of the VSD with color Doppler flow evaluation of shunt flow by proximal isovelocity surface area (PISA) has changed traditional views about preoperative studies. Thus, cardiac catheterization and cineangiography are not necessary before closure of primary VSDs when (1) the clinical syndrome in neonates and infants indicates a large ; (2) noninvasive imaging clearly defines the morphology, including that of the aortic arch and ductus arteriosus; and (3) the surgeon is experienced in surgical identification and repair of congenital heart disease.

For identifying a large single perimembranous VSD, combined 2D echocardiography and Doppler flow interrogation is highly reliable in combination with clinical criteria ( Fig. 35-18 ). Echocardiography adds to anatomic clarification, particularly in the case of doubly committed subarterial VSDs. Particularly for small VSDs and multiple muscular defects, 2D Doppler color flow echocardiographic imaging increases the sensitivity of echocardiography ( Fig. 35-18, A and B ). However, and particularly in the presence of a single large VSD, multiple muscular defects can go undetected even with refined techniques of echocardiography. Because perimembranous VSDs are infrequently (<3% ) accompanied by additional muscular VSDs, this does not contraindicate proceeding to repair in infants without cardiac catheterization. Malalignment VSD is diagnosed by 2D echocardiography by the appearance of the alignment of the RV trabecular septum with the outlet septum. Malalignment may be anterior as in tetralogy of Fallot ( Fig. 35-18, C ), posterior as in interrupted aortic arch, or rotational as in Taussig-Bing heart.

Size of a VSD is generally categorized echocardiographically as small, moderate, or large for purposes of decisions regarding surgery (see Morphology and Indications for Operation later in this chapter). A large defect has a diameter of 75% or greater of the aortic anulus and low-velocity flow by Doppler, measuring no more than 1 m · s ⁻¹ . A moderate defect has a diameter of 33% to 75% of the aortic anulus and flow velocity of 1 to 4 m · s ⁻¹ , indicating moderate flow restriction. (By the modified Bernoulli equation, gradient across the defect is calculated by multiplying velocity squared times 4.) A small defect has a diameter less than 33% of the aortic anulus and a flow velocity of 4 m · s ⁻¹ or greater. When considering Rp, it is important to note that as resistance (or obstructions in the RV outflow tract) increases, flow velocity across the VSD decreases.

Other Noninvasive Diagnostic Methods

Other noninvasive imaging modalities may come into use. At present, only magnetic resonance imaging (MRI) has shown promise to provide accurate information about the morphology of all types of VSDs. Dynamic three-dimensional echocardiographic reconstructions may refine ability to image and portray VSDs spacially.

Cardiac Catheterization

When surgical intervention is under consideration in older children, cardiac catheterization and angiography are generally indicated to assess Rp and precisely identify location, size, and number of VSDs and any associated anomalies. Furthermore, preoperative sizing of VSDs is often important in arriving at management decisions. Sizing can be especially difficult when the VSD is associated with another lesion such as coarctation or pulmonary stenosis. The most reliable way to size the defect is to measure its diameter either by 2D color flow Doppler echocardiography or cineangiography. With cineangiography, the VSD must be accurately profiled and the measurement either corrected to allow for magnification or compared with aortic root diameter. In applying this method to perimembranous VSDs, the defect is smaller in a cranially tilted left anterior oblique (LAO) projection than in the conventional LAO position.

Cardiac catheterization should include both right-sided and left-sided heart studies, the latter mainly to obtain LV angiograms. Basic data obtained at cardiac catheterization should include oxygen consumption ( ); systolic, diastolic, and mean pulmonary arterial, pulmonary artery wedge, and systemic arterial pressures; oxygen content and saturation in right atrial, pulmonary arterial, aortic, or peripheral arterial blood and, when possible, left atrial blood. Pulmonary ( ) and systemic ( ) blood flows and are calculated ³ with Rp ( Table 35-3 ). When left atrial (or pulmonary arterial wedge) pressure is not available, only total pulmonary resistance (TPR) ⁴ can be calculated. Rp in absolute units × body surface area is of more value in predicting operability than is the ratio of resistances in pulmonary and systemic circuits. When Rp is elevated, further information concerning operability should be obtained by assessing response to exercise and to isoproterenol (see Indications for Operation later in this chapter).

Angiography

3

where pv is pulmonary vein and pa is pulmonary artery.
may be expressed as index (L · min ⁻¹ · m ⁻² ) by dividing by body surface area (BSA) expressed in square meters.

where a is aorta or arterial and
is mixed venous.

Note that total oxygen consumption is not needed for this calculation.

4

Angiographic assessment of VSD is best performed using biplane techniques in appropriate projections. Whereas cardiologists and radiologists carry primary responsibility for these studies, appreciation of their findings and limitations is essential to the surgeon, who must also understand when the study is incomplete.

Fig. 35-19 summarizes the surgically important features of angiograms of VSD by diagram. Fig. 35-20 presents representative angiograms of the various types of VSDs.

Spontaneous Closure

VSDs tend to close spontaneously. This is relevant to decisions about operation and explains, for the most part, the infrequency with which large VSDs are encountered in adults. Spontaneous closure can be complete by 1 year of age, or the defect may have only narrowed by then, with complete closure taking considerably longer. An inverse relation exists between the probability of eventual spontaneous closure and age at which the patient is observed ( Fig. 35-21 ). About 80% of patients with large VSDs seen at age 1 month experience eventual spontaneous closure, as do about 60% of those seen at age 3 months, about 50% of those seen at age 6 months, and about 25% of those seen at age 12 months. This decreasing tendency for spontaneous closure of a VSD as the patient grows older has also been confirmed by Beerman and colleagues, and spontaneous closure has been documented to occur in only one patient between age 21 and 31 years. Onat and colleagues studied 106 children with VSD and concluded that these patients should be followed closely through adolescence because the defects may decrease in diameter, shunt flow may diminish, and spontaneous closure may be expected in 23% of patients.

The mechanism of narrowing or closure of perimembranous VSDs is usually adherence of tricuspid leaflet or chordal tissue to the edges of the VSD. Closure has erroneously been related to echocardiographic diagnosis of aneurysm of the membranous septum. Aneurysm of the membranous septum is usually considered benign and functionally reduces the size of the VSD. It has the potential consequence of promoting tricuspid regurgitation and RV outflow tract obstruction and is a nidus for infective endocarditis.

Perimembranous VSDs, as well as VSDs that are juxta-aortic and inlet VSDs of the AV septal type, are less likely to close than juxtatricuspid or subarterial muscular VSDs. Perimembranous VSD with LV-to–right atrial shunt (Gerbode defect) in infancy is also associated with less chance of spontaneous closure.

Inferences about the tendency toward spontaneous closure seem to be in disagreement with the results of some studies. Hoffman and Rudolph's data (one of the sources for Fig. 35-21 ) indicate that 80% of infants aged 6 weeks with large VSDs will experience spontaneous closure or reduction in size of the VSD. Rowe found that none of 11 infants (mean age 46 days) with a VSD 80% or greater in diameter than that of the aorta showed subsequent reduction in size during the period of observation. These apparent discrepancies may be explained by lack of information about location or size of VSDs.

Pulmonary Vascular Disease

A large VSD exposes the patient to risk of developing increased Rp from hypertensive pulmonary vascular disease, which tends to worsen with age. Thus, the proportion of patients with large VSDs who have severely elevated Rp is directly related to age ( Fig. 35-22 ). The statement that some infants younger than 2 years of age with large VSDs have severely elevated Rp is doubted by some, but its occurrence is well documented.

Some infants and children with severely elevated Rp have not undergone the usual fall in Rp a few weeks to a few months after birth. Others have undergone this decrease, but later in the first 2 years of life, they have developed a rapid increase in Rp.

Some infants with large VSDs and most of those with moderate-sized VSDs have normal or mildly elevated Rp and retain this through the first decade of life. Then, if their VSD is still large, more severe pulmonary vascular changes may or may not develop as they age. In infants with small VSDs, pulmonary vascular disease does not develop.

Infective Endocarditis

Infective endocarditis is rare in patients with VSD, occurring at a rate of about 0.15% to 0.3% per year. Its prevalence is greater in males and individuals older than 20 years of age. Infective endocarditis is more common in small and moderate VSDs than in large VSDs. Often a pulmonary process is the presenting feature, presumably developing from emboli secondary to right-sided bacterial vegetations or bacteria carried to the lungs by left-to-right–directed flow through the VSD. Prognosis with modern antibiotic treatment regimens is good.

Premature Death

Past experience and reports in the literature indicate that without surgical treatment, about 9% of infants with large VSDs die from them in the first year of life. Death may result from heart failure, which may develop very early but usually occurs at about age 2 to 3 months, presumably because at that time the left-to-right shunt increases as the medial hypertrophy present in the small pulmonary arteries at birth regresses. Death may also result from recurrent pulmonary infections, often viral in origin, secondary to pulmonary edema from high pulmonary venous pressure. Death is most likely to occur in those infants with large VSDs who have associated conditions of major anatomic or functional importance, such as PDA, coarctation of the aorta, or large atrial septal defect.

After the age of 1 year, few if any patients die of their VSD until the second decade of life. By then, many patients whose VSDs have remained large have pulmonary vascular disease and ultimately die with complications of Eisenmenger complex ( Fig. 35-23 ). These include hemoptysis, polycythemia, cerebral abscess or infarction, and right-sided heart failure.

Patients with small VSDs die very rarely as a result of bacterial endocarditis. However, in common with patients with larger VSDs, some of these patients may develop disturbed systolic function and increased compliance in both ventricles.

Clinical Course

Patients with small VSDs rarely have symptoms related to the defect. Those with large VSDs may have symptoms of intractable heart failure in the first few months of life, with poor peripheral pulses, inability to feed, sweating, and chronic pulmonary edema. About half the patients coming to operation in the first 2 years of life do so because of intractable heart failure. During early life, rapid and labored respiration and recurrent pulmonary infections may occur secondary to high pulmonary venous pressure and chronic pulmonary edema. Lobes of the lung may become chronically hyperinflated because of pressure of the large and tense pulmonary arteries on the bronchi, preventing complete escape of air during expiration. All this causes many babies with large VSDs to be small and physically underdeveloped. Symptomatic patients who fail to respond well to medical management are at particular risk of dying in the first year of life. Some babies who survive through the first year of life with large VSDs have controlled heart failure and failure to thrive in the second year of life as well.

Children and young adults with large VSDs are usually symptomatic and tend to be small in both height and weight. As pulmonary vascular disease develops, symptoms may regress.

Development of Aortic Regurgitation

See Section II: Ventricular Septal Defect and Aortic Regurgitation

Development of Infundibular Pulmonary Stenosis

A small proportion (5%-10%) of patients with large VSDs and large left-to-right shunt in infancy develop infundibular pulmonary stenosis. The mild and moderate infundibular pulmonary stenoses in patients operated on for primary VSD, as well as some of the more important pulmonary stenoses, probably develop in this way. Stenosis may become severe enough to produce shunt reversal and cyanosis, and the condition then can properly be termed tetralogy of Fallot (see Chapter 38 ). Those who undergo the transformation probably are born with a mild degree of anterior displacement of the infundibular septum and its extensions.

Repair of Perimembranous Ventricular Septal Defect

After CPB (with or without circulatory arrest) has been established, the aorta is occluded, cold cardioplegic solution injected, and the right atrium opened obliquely. A suction device is placed across the naturally present or surgically created foramen ovale ( Fig. 35-24 ). Before repair is started, the defect is carefully examined to establish that all margins can be seen and reached. In rare circumstances in which this is not possible because of chordal arrangement, an incision is made to disconnect a portion of the tricuspid valve from the anulus, and the VSD is exposed through the resulting aperture. Particular attention is directed toward determining whether the VSD is juxtatricuspid, in which case it abuts the tricuspid valve in the region of the commissure between septal and anterior leaflets. If the VSD has a bar of muscle of varying width between it and the tricuspid valve, it is not juxtatricuspid. Relationship of the bundle of His to the posterior and inferior margins of the defect must be clearly understood (see Morphology earlier in this section) to accomplish a safe repair ( Fig. 35-24, A ).

In older infants and children, the VSD is repaired with a polyester patch sewn in place with continuous polypropylene sutures ( Fig. 35-24, B ), a technique confirmed to be entirely adequate in such patients. In neonates and small infants, the technique may not be adequate because of the delicate nature and friability of the structures. In these patients, the patch may be sewn into place using a combination of continuous and interrupted pledgeted mattress sutures or, alternatively, employing exclusively interrupted mattress sutures reinforced with small pledgets.

A ventricular approach may be used when the VSD cannot be well visualized from the right atrium. An RV approach is performed through a transverse incision. The patch is sewn into place with continuous or interrupted sutures ( Fig. 35-25 ). Technique of repair and sequence for suturing shown in Fig. 35-25 are slightly different from those shown for the atrial approach. Suturing begins at the transition point between the septal leaflet of the tricuspid valve and the ventricular septum, 5 to 7 mm below the edge of the septal defect. This critical point is given attention by all experienced surgeons.

Usual de-airing procedures are performed, and the remainder of the operation is completed as usual.

Repair of Doubly Committed Subarterial Ventricular Septal Defect

Transverse incision in the RV infundibulum is the classic approach for repair of doubly committed subarterial VSDs ( Fig. 35-26 ). These defects should always be closed with a patch to reduce the possibility of distorting the semilunar valves. A continuous stitch technique is employed. When pledgeted sutures are used, they are placed from just above the pulmonary valve leaflets, and pledgets come to lie in the pulmonary valve sinuses. Care is taken not to damage the left main coronary artery. An approach through the pulmonary trunk is also convenient for repairing doubly committed subarterial VSDs.

Repair of Inlet Septal Ventricular Septal Defect

Inlet septal (AV septal type) VSD is most easily repaired through the right atrium (see Technique of Operation in Chapter 34 ). Such defects are always repaired with a patch. The defect lies beneath the septal leaflet of the tricuspid valve, and care is taken to avoid damage to the leaflet or its chordae and to tailor the patch such that it is not too bulky beneath the leaflet. One method of avoiding damage to the leaflet and improving exposure is to temporarily detach the base of the septal leaflet and a portion of the anterior leaflet of the tricuspid valve and retract the leaflet anteriorly.

Repair of Muscular Ventricular Septal Defect

A right-sided approach is used for repair of muscular VSDs. Left ventriculotomy provides excellent exposure, and although it has been reported not to be disadvantageous in infants, it can produce ventricular aneurysm and important LV dysfunction early and late postoperatively. Therefore, use of left ventriculotomy is not recommended. Defects in the lower part of the muscular septum may be obscured by trabeculations and thus difficult to visualize, resulting in incomplete closure. Wollenek and colleagues found that an apical left ventriculotomy was a useful approach in 23 patients, and in follow-up over 3 to 18 years (mean 11 years), echocardiography showed no residual VSD, normal LV shortening, no regional wall motion abnormality, and small LV aneurysm in only two patients.

Single or multiple muscular defects in the inlet and trabecular septum (see Figs. 35-1 and 35-12 ) are approached through the right atrium. When a single defect is slitlike or oval, direct suture (often in part at least with pledgeted mattress sutures) is satisfactory, but when it is large and circular, a patch is used. A cluster of defects can be closed with a single patch or individually.

Division of RV trabeculations can aid exposure of the defects, which may be difficult to close because of multiple sites of jet penetration. A heavy traction stitch passed through the defect and back through the left side of the defect may improve exposure. A single patch of autologous pericardium supported by pledget-reinforced sutures covering an extensive portion of the trabecular septum is useful when there are multiple defects. Kitagawa and colleagues described resection of trabeculations to expose the defect and attaching an oversized patch to the left side of the ventricular septum by sutures passed through the septum from the left side. They also described placing pledget-supported sutures through the rim of an anterior muscular defect, passing the sutures to the outside and tying down on the epicardial surface. ⁵

5 The pledget is a “firm” polyester mini-pledget, inch × inch × inch.

When a muscular VSD coexists with a perimembranous VSD, a single patch may be used to avoid damaging the bundle of His.

VSDs with a single LV opening but two or more openings into the RV on both sides of the trabecula septomarginalis are also approached through the right atrium. The defect is converted into a single LV orifice by detaching the lower end of the trabecula septomarginalis and moderator band from the septum and retracting them (see Fig. 35-12 ). The VSD is closed with a patch. The trabecula septomarginalis then falls back into place.

Multiple defects in the anterior portion of the septum may be closed through a high transverse ventriculotomy. At times, VSDs may be considered too numerous to close individually; these VSDs are simply compressed and often totally closed by interrupted mattress sutures between a felt strip on the anterior ventricular wall (away from the left anterior descending coronary artery) and pledgets inside the RV and inferior to the VSDs. This repair may be done from the right atrium or through a right ventriculotomy.

Apical muscular VSDs can be exposed through the right atrium and tricuspid valve or through a low vertical right ventriculotomy. This can be extended around the apex for a short distance onto the posterior wall.

The rare Swiss cheese septum, with features resembling ventricular noncompaction (spongy ventricular septum) and defects involving all components of the ventricular septum, may not be correctable through the right side. Its repair requires an LV approach, and a patch over the entire muscular septum may be necessary. An associated perimembranous defect should be repaired through the right atrium because its repair from the LV side increases risk of heart block. Incisions into both ventricles are avoided whenever possible. Great care is used in making and closing the left ventriculotomy incision so as not to damage coronary artery branches. A continuous mattress suture over fine polytetrafluoroethylene (PTFE) felt strips plus an over-and-over stitch give a secure closure. Mace and colleagues used a right atrial approach and inserted a single large patch to cover the right side of the trabecular septum, adding several intermediate fixation stitches to prevent septal bulging. Regardless of the approach employed, these patients often have poor LV function after repair and may ultimately require transplantation for heart failure. This group of patients may be better served by pulmonary trunk banding with the hope that some of these defects may close as a result of ventricular hypertrophy.

Although it is important to avoid residual shunts, multiple incisions and a prolonged search for a few small additional muscular VSDs are generally not advisable. Preoperative echocardiography should accurately delineate the size as well as position of all the defects.

Closure of Associated Patent Ductus Arteriosus

Dissection of the ductus arteriosus is done after establishing CPB; this reduces the risk of hemorrhage should an error in dissection occur because of exposure, which can be difficult. After establishing CPB with the perfusate temperature at about 34°C, with caval tapes still unsnugged (so the heart will not distend) and right atrial pressure at zero, the ductus is dissected. The heart must continue to beat; otherwise a large shunt will rapidly overdistend the right side of the heart and lungs as it steals from the systemic and cerebral circulation. If the heart does fibrillate, CPB flow is immediately reduced while the dissection is rapidly completed. With downward traction on the pulmonary trunk (see Technique of Operation in Chapter 37 ), the ductus can usually be seen through its pericardial reflection and surrounding adventitial tissue. The left pulmonary artery and undersurface of the aorta—both proximal and distal to the ductus—are clearly identified to prevent these structures from being damaged or ligated after being mistaken for the ductus. The delicate pericardial reflection and adventitial tissue on both sides of the ductus are sharply dissected from it. The adventitia of the ductus itself and of the adjacent pulmonary artery and aorta must not be entered. The recurrent laryngeal nerve is not seen. Only when the dissection is complete, the left pulmonary artery visualized, and the ductus identified with absolute certainty is a right-angled clamp passed behind it to grasp the 2-0 silk ligature. One ligature, tied on the ductus while CPB flow is reduced to lower intravascular pressure, is sufficient to close it. A surgical clip may be used instead. The operation then proceeds as usual.

Pulmonary Trunk Banding

Banding of the pulmonary trunk may be performed through a small left anterolateral thoracotomy. However, now that pulmonary trunk banding is reserved for special situations, often to be followed by a Fontan operation (see “Pulmonary Trunk Banding” in Section II of Chapter 41 ) or use of a valved conduit, avoiding distortion of the pulmonary trunk bifurcation by the band is crucial. To ensure this, placement of the pulmonary trunk band via median sternotomy is the best approach because it permits accurate dissection, placement, and anchoring of the band on both the left and right sides of the pulmonary trunk.

According to Trusler's rule , in the case of patients with a two-ventricle circulation, the pulmonary trunk band is marked to a length of 20 mm, plus the number of millimeters corresponding to the child's weight in kilograms, to indicate the ultimate tightness of the band. If the banding is done for a complex cardiac anomaly with mixed circulation, the length is 24 mm plus the child's weight. A 3- to 4-mm-wide tape is used. The preferred material for the band is silicone or silicone-impregnated polyester, which minimizes erosion into the pulmonary trunk and allows easy removal.

When a left anterolateral thoracotomy is used, a small incision is made in the pericardium, generally anterior to the phrenic nerve. When a median sternotomy is used, the pericardium is opened in the midline. To minimize subsequent adhesions, the pericardial incision should be limited to the area needed to expose the great vessels. The pulmonary trunk is separated from the aorta by dissecting close to the aorta . A right-angled clamp is passed around and behind the aorta to grasp one end of the band and pull it through. The other end of the band is retrieved by a clamp passed through the transverse sinus. Small angiocatheters are placed in the aorta and left pulmonary artery for pressure monitoring. Transesophageal echocardiography (TEE) may be useful during the procedure to estimate gradient across the band.

With the band now safely around the proximal portion of the pulmonary trunk, the marked points on the band are joined temporarily with a hemoclip to produce the desired circumference. With proper band tightening in patients with a two-ventricle circulation, systolic and mean blood pressures rise, but systemic oxygen saturation should remain at 100%. If systemic oxygen saturation drops below 100%, the will be less than 1, and the band is too tight. The distal pulmonary artery systolic pressure should be less than 50% of systemic systolic blood pressure. In cases of complete mixing, arterial oxygen saturation will vary with band tightening and should be set at 80% to 85% by pulse oximetry with F io ₂ of 50%. This implies a of about 1 (see “Pulmonary Trunk Banding in Section II of Chapter 41 ). If bradycardia or cyanosis develops, the band must be slightly loosened by placing a hemoclip more distally and removing the initial clip. If the narrowing is insufficient, as judged by the criteria mentioned earlier, it is tightened by adding a hemoclip more proximally.

When the ideal diameter is obtained, the band is joined by sutures. It is essential that stitches be placed between the band and the pulmonary trunk adventitia to prevent migration of the band. The pericardium is loosely closed to facilitate dissection at subsequent operation.