Total Anomalous Pulmonary Venous Connection

Pulmonary Venous Anatomy

TAPVC is supracardiac in about 45% of cases, cardiac in about 25%, infracardiac in about 25%, and mixed in about 5% to 10% ( Fig. 31-1 ). The connection in supracardiac TAPVC is usually to a left vertical vein draining into the left brachiocephalic vein, less often to the superior vena cava, usually at its junction with the right atrium, and rarely to the azygos vein. In cardiac TAPVC, the connection is usually to the coronary sinus and less often to the right atrium directly. Connection to the supradiaphragmatic inferior vena cava also has been reported. The most common sites of connection in patients with infracardiac (infradiaphragmatic) TAPVC are the portal vein (65% of cases, according to Duff and colleagues ) and ductus venosus; less common are the gastric vein, right or left hepatic vein, and inferior vena cava. Uncommonly, the pulmonary venous drainage may be through two connections. Also, part of the pulmonary venous drainage may be to one site and part to another in what is termed mixed TAPVC . At least 15 different morphologic mixed variants have been identified. In the most common form, the left upper lobe of the lung drains to a left vertical vein, and the remainder of both lungs drains to the coronary sinus. In the next most common form, the right lung drains to the coronary sinus, and the left lung drains to a vertical vein. Chowdhury and colleagues have categorized this wide assortment of mixed TAPVC into three general groups: the 2+2 pattern, the 3+1 pattern, and the bizarre pattern.

No matter what the final connection or termination may be, individual right and left pulmonary veins usually converge to form a common pulmonary venous sinus, which in turn connects to the systemic venous system in one of the ways noted earlier. It is usually posterior to the pericardium. Its long axis is usually oriented transversely, with the pulmonary veins of the left lung converging to form its left extremity and those from the right lung to form its right extremity. When the drainage is infracardiac, the right and left pulmonary veins slope downward to converge into a vertical sinus, with the entire arrangement having a Y, T, or tree shape. Rarely, there are two vertical veins that are not confluent until below the diaphragm. Two vertical veins have also been identified in supracardiac TAPVC.

A common pulmonary venous sinus may be absent in some cases with cardiac or mixed connections. Its apparent absence in some patients may be an illusion attributable to a defect in the anterior wall of the sinus. That defect is the orifice connecting it to the coronary sinus or right atrium. Pulmonary venous obstruction is a severe associated condition usually resulting from a stenosis involving the vein connecting the common pulmonary venous sinus to the systemic venous system. A localized stenosis may occur at the junction of the left vertical vein with either the left brachiocephalic vein or the common pulmonary venous sinus, or at the junction of a connecting vein that joins the superior vena cava. Severe obstruction may be due to the so-called vascular vice, in which the left vertical vein passes posterior rather than anterior to the left pulmonary artery and is compressed between it and the left main bronchus.

When TAPVC is to the coronary sinus, a stenosis may occur where the common pulmonary venous sinus joins the coronary sinus or (rarely) at the coronary sinus ostium. In infracardiac connection, the connecting vein may be similarly narrowed at its junction with the portal vein or ductus venosus, or it may be compressed where it penetrates the diaphragm. In those varieties of infracardiac connection in which the ductus venosus is not available to bypass the liver, the portal sinusoids offer additional important obstruction to venous return. Finally, pulmonary venous obstruction may result simply from the length of a comparatively narrow connecting vein. Rarely, associated cor triatriatum is present and serves as the cause of obstruction.

Important pulmonary venous obstruction of these various types exists in nearly all patients with infracardiac connection and in almost all with connections to the azygos vein, in 65% of those with connections to the superior vena cava, in 40% of those with connections to the left brachiocephalic vein, and in 40% with connections of the mixed type. It is less common in patients with a cardiac connection, although it has been found in 20% of patients in whom the connection is to the coronary sinus. Rarely, pulmonary venous obstruction is the result of stenoses of individual pulmonary veins at or close to their connections to the common pulmonary venous sinus. Functional pulmonary venous obstruction arguably occurs in patients having a patent foramen ovale rather than an atrial septal defect, although this occurrence may be limited to those with a small orifice at the foramen ovale.

Cardiac Chamber and Septal Anatomy

For survival after birth, a communication between systemic and pulmonary circulations must exist. Nearly always, an atrial septal defect or patent foramen ovale is present. However, in the review of Delisle and colleagues, one of 93 autopsy cases was an 11-year-old with an intact atrial septum and multiple ventricular septal defects, and Hastreiter and colleagues reported a 6-week-old patient with TAPVC to the ductus venosus, a patent ductus, and a closed foramen ovale. Atrial communication in TAPVC is usually of adequate size and not obstructive, although the GLH group reported that the defect was small in about half the infants operated on. There is frequently no pressure gradient between the two atria even when the defect is small.

The right atrium is enlarged and thick walled in patients with TAPVC, and the left atrium is abnormally small. Cineangiographic studies by Mathew and colleagues have shown left atrial volume to be 53% of predicted normal. These investigators noted that the left atrial appendage was normal in size and believed that left atrial smallness could be explained by absence of the pulmonary vein component. In addition, in patients with TAPVC to the right atrium, the posterior attachment of the atrial septum is shifted to the left, so the septum lies nearer to the sagittal than the usual coronal plane. Anatomic studies have shown that the left ventricle (LV) is usually normal in size. Haworth and Reid's quantitative study showed that inflow measurements of the LV were normal in eight of nine infants dying with TAPVC. In one infant, however, LV inflow measurements were abnormally small, and weight of the free LV wall plus the septum was less than that of a normal fetus at full term. In all nine infants, LV free-wall thickness was normal. In a quantitative autopsy study of infants with TAPVC, Bove and colleagues found LV mass to be normal as well. However, they found the LV cavity was small because of leftward displacement of the septum secondary to right ventricular (RV) pressure-volume overload (see “Mitral Prolapse” under Morphology in Chapter 30 ). Correspondingly, Nakazawa and colleagues reported that angiographically determined LV end-diastolic volume (LVEDV) was 79% less than normal ( P = .009) in a group of infants with TAPVC and severe pulmonary hypertension. Hammon and colleagues also reported small LVEDV in infants with TAPVC. These findings are all compatible with those of Whight and colleagues ( Fig. 31-2 ).

The RV varies in size, depending on the magnitude of pulmonary blood flow, presence or absence of pulmonary venous stenosis, and the point at which anomalous pulmonary veins connect. When connection was infracardiac, Haworth and Reid found that the RV was neither hypertrophied nor dilated. When venous connection was supradiaphragmatic, the septum and RV were hypertrophied and the RV dilated.

Pulmonary Vasculature

Because most infants with TAPVC have marked pulmonary hypertension, structural changes are usually found in the lungs of even the youngest infants dying with the malformation. Haworth and Reid demonstrated increased pulmonary arterial muscularity in all infants dying with TAPVC, including an 8-day-old neonate, as shown by increased arterial wall thickness and extension of muscle into smaller and more peripheral arteries than normal. Vein wall thickness was increased in all but the youngest child.

Associated Conditions

Except for an atrial communication, most infants presenting with severe symptoms from TAPVC have either no associated condition or a small or large patent ductus arteriosus. Patent ductus arteriosus is present in nearly all infants coming to operation in the first few weeks of life with pulmonary venous obstruction and, overall, in about 15% of cases. Ventricular septal defects occasionally occur. However, more than one third of cases coming to autopsy, few of which are infants, have other major associated cardiac anomalies. These include tetralogy of Fallot, double-outlet RV, interrupted aortic arch, and other lesions. The combination of TAPVC with other major cardiac anomalies is especially likely to occur when there is atrial isomerism (see Chapter 58 ). Other associations have been identified. Esophageal varices can occur in obstructed TAPVC, and these are likely caused by obstructed veins. Hypoplasia of the small pulmonary arteries has recently been identified in obstructive TAPVC.

Presentation

Patients with TAPVC present as seriously and often critically ill neonates, especially when a component of obstruction is present. The diagnosis can be missed when obstruction is absent, because of lack of florid signs and symptoms. TAPVC must be suspected in any neonate who has unexplained tachypnea, the cardinal sign of this anomaly. During the first 2 weeks of life, there are other causes of tachypnea that may be impossible to distinguish clinically from TAPVC, particularly a diffuse pneumonic process and retention of fetal lung fluid. Meconium aspiration and myocarditis may also confound the diagnosis. Respiratory distress syndrome should not be difficult to differentiate, because of its classic radiologic features, prematurity, and intercostal and sternal indrawing. Cyanosis is usually unimpressive in TAPVC unless there is marked pulmonary venous obstruction or a widely open ductus arteriosus that permits right-to-left shunting. Both LV and RV functions are depressed compared with normal ( P < .001 in both instances) in infants presenting when seriously ill with obstructed TAPVC and marked pulmonary hypertension. Severe metabolic acidosis develops soon after birth when pulmonary venous obstruction is severe, rapidly leading to myocardial necrosis. Some neonates are so critically ill that they require intubation immediately upon hospital admission and before evaluation is begun.

Examination

In neonates and infants, the heart is not particularly overactive on examination. There may be an unimpressive precordial systolic murmur and gallop sound (the latter often proves to be a tricuspid flow murmur). The second heart sound is usually single or narrowly split. In older children, the signs are those of a large atrial septal defect unless there is increased pulmonary vascular resistance.

Chest Radiography

On chest radiography, heart size is usually near normal if there is pulmonary venous obstruction, but it may be large when there is increased pulmonary blood flow. The latter is associated with plethora ( Fig. 31-3, A ), but the more common pulmonary venous obstruction is evident as a diffuse haziness or, in its severe forms, a “ground glass” appearance. This sign is reduced when the pulmonary circuit can decompress via a patent ductus arteriosus. Older infants with TAPVC to the left brachiocephalic vein have a characteristic “figure-of-eight” or “snowman” configuration on the chest radiograph ( Fig. 31-3, B ).

Echocardiography

Two-dimensional (2D) echocardiography is remarkably accurate in assessing the morphology of TAPVC ( Fig. 31-4 ). Along with Doppler color flow interrogation, it is almost always diagnostic. Echocardiographic features include criteria for RV diastolic overload and an echo-free space posterior to the left atrium. However, a second drainage site might be overlooked. Echocardiography is commonly accepted as a definitive diagnostic procedure in neonates with important pulmonary venous obstruction, because contrast medium is not required. Cardiac catheterization delays operation and exacerbates myocardial failure and pulmonary edema.

Cardiac Catheterization and Cineangiography

Angiograms obtained by pulmonary artery or pulmonary vein injections define the malformation, identify the site of drainage, and often localize the site of pulmonary venous obstruction. This procedure is nearly always diagnostic. However, it should not be used in seriously ill neonates (see previous discussion). When the connection is to a left vertical vein, the common pulmonary venous sinus and vertical vein can usually be demonstrated ( Fig. 31-5, A ). When the anomalous connection is to the coronary sinus, it appears as an ovoid opacification over the left side of the spine within the right atrial contour. When it is infracardiac, the descending vein can usually be demonstrated, although its precise infradiaphragmatic connection may not be seen ( Fig. 31-5, B ).

Tynan and colleagues have pointed out that in neonates, umbilical vein catheterization permits direct injection of contrast medium into the anomalously connecting infradiaphragmatic vein and an accurate diagnosis of its connections. Presence of pulmonary venous obstruction is established by demonstrating a gradient between left atrial and pulmonary artery wedge pressures. Greene and colleagues employ superimposition digital subtraction angiography to define pulmonary venous anatomy, relationship of common pulmonary vein to left atrium, and size of left atrium.

Magnetic Resonance Imaging and Computed Tomography

Because of diagnostic limitations of echocardiography in complex cases and morbidity associated with cardiac catheterization in gravely ill patients, both magnetic resonance imaging (MRI) and computed tomography (CT) have become increasingly important in diagnosing TAPVC. Both modalities should be used selectively, primarily in patients in whom echocardiography is not definitive. When compared with both catheterization and echocardiography, numerous studies have demonstrated the accuracy of MRI and CT in diagnosing TAPVC. Several demonstrate improved accuracy of diagnosis using both helical CT angiography, with and without three-dimensional (3D) reconstruction, and gadolinium-enhanced 3D cardiac magnetic resonance (CMR) angiography.

Physiology of Common Mixing Chamber

In TAPVC, the right atrium is theoretically a common mixing chamber. This situation is reflected in the frequent finding of close similarity of oxygen content and saturations from the right atrium, left atrium, pulmonary artery, and systemic artery. There is considerable deviation from this pattern, however, because of streaming of systemic venous return in the right atrium, directing inferior vena caval blood through the foramen ovale to the mitral valve, and superior vena caval blood through the tricuspid valve. Thus, in infracardiac TAPVC, systemic arterial saturation is typically higher than pulmonary artery saturation.

Because TAPVC has this common mixing chamber, in most patients who live beyond infancy, a direct relationship exists between the magnitude of pulmonary blood flow and arterial oxygen saturation, assuming a constant oxygen consumption and blood hemoglobin level. This relationship was formulated into a nomogram by Burchell ( Fig. 31-6 ). Because the pulmonary/systemic blood flow ratio ( ) in such patients is determined primarily by magnitude of the pulmonary blood flow, and because their pulmonary vascular resistance is inversely related to pulmonary blood flow, arterial oxygen saturation in children (not in seriously ill neonates and young infants) is a rough guide to the patient's operability vis-à-vis pulmonary vascular disease. When, in children and adults, arterial oxygen saturation is less than about 80%, the is likely to be less than 1.4 and pulmonary vascular resistance greater than 10 U · m ² .

Total Anomalous Pulmonary Venous Connection to Left Brachiocephalic Vein

After sternotomy and anterior pericardotomy, the common pulmonary venous sinus, lying behind the pericardium, is identified after lifting up the apex of the heart for a moment to visualize the retrocardiac portion of the pericardium. The right pulmonary artery, running parallel and just cephalad to the sinus, is also identified to avoid confusing it with the common pulmonary venous sinus. The vertical vein connecting the common pulmonary venous sinus to the left brachiocephalic vein can sometimes be seen inside the pericardium, but in most cases the pericardium on the left must be retracted toward the patient's right and the persistent left vertical vein identified beneath the mediastinal pleura. The vein is isolated after carefully freeing the left phrenic nerve. A ligature is tied to the tip of the left atrial appendage for leftward retraction.

CPB and cardiac arrest are established using the techniques described in the previous section. The ductus arteriosus (if patent) and persistent vertical vein are ligated. The common pulmonary venous sinus can be exposed in several ways. One method approaches the common pulmonary venous sinus from the right side of the heart. The posterior pericardial reflection is opened ( Fig. 31-9, A ), and the common pulmonary venous sinus is mobilized and opened ( Fig. 31-9, B-C ). The posterior left atrial wall is opened, and the anastomosis is then made between the common pulmonary venous sinus and left atrium ( Fig. 31-9, D-F ). The continuous suture line must not be pulled up so tightly as to purse-string the anastomosis and narrow it. The right atrium is opened, the foramen ovale closed, and the atrium closed. The remainder of CPB and reestablishment of myocardial perfusion are completed (see Chapter 2, Chapter 3 ).

A second method of repairing TAPVC is similar to that just described, but the common pulmonary venous sinus is exposed from the left side of the heart by lifting the cardiac mass out of the pericardial sac by retracting the cardiac apex anteriorly and rightward. This is best achieved by placing a retracting suture into the apical myocardium ( Fig. 31-10, A ). This avoids the warming effect on the myocardium that occurs when the surgical assistant's finger or hand is used to directly retract the heart. The pericardial sac is now essentially vacant, and the incision in the common pulmonary venous sinus is made under direct vision ( Fig. 31-10, B ). The back of the left atrium is also exposed by this maneuver and is incised. The anastomosis is then made in a fashion similar to that described in the preceding text ( Fig. 31-10, C ).

A third method of repairing TAPVC to the left brachiocephalic vein is via a right atrial approach. This method has the advantage of allowing the anastomosis of the common pulmonary venous sinus to the left atrium to be performed in precise anatomic relationships, because there is no retraction or displacement of critical structures to gain exposure. The right atrium is incised parallel to the atrioventricular groove ( Fig. 31-11, A ), exposing the atrial septum. The membrane of the foramen ovale is excised to gain entry to the left atrium. The posterior wall of the left atrium is incised transversely ( Fig. 31-11, B ) into the free pericardial space behind the atrium. The common pulmonary venous sinus is identified lying beneath the pericardium directly behind the incision in the left atrium. An incision is made in the common pulmonary venous sinus, which extends from the bifurcation on the left side to the bifurcation on the right side (see Fig. 31-11, C ). A large anastomosis is constructed between the common pulmonary venous sinus and left atrium ( Fig. 31-11, D ). This anastomosis has little chance for distortion because it is performed without displacing anatomically adjacent structures. Repair is completed by closing the foramen ovale with a pericardial patch ( Fig. 31-11, E ). The patch serves both to repair the atrial septum and enlarge the left atrial filling capacity.

Total Anomalous Pulmonary Venous Connection to Superior Vena Cava

A common pulmonary venous sinus is usually present in the rare anomaly of TAPVC to the superior vena cava, providing free communication between right and left pulmonary veins. After the presence of this sinus is confirmed by direct inspection (see “ Total Anomalous Pulmonary Venous Connection to Left Brachiocephalic Vein ” earlier), the operation proceeds in the same manner as described for patients with TAPVC to the left brachiocephalic vein, using the right atrial approach. The connection into the lower part of the superior vena cava is identified, and palpation is performed with a right-angled clamp to confirm the anatomic details. The sinus is disconnected from the superior vena cava by cutting across the connection. The resultant opening in the sinus is extended in both directions and the sinus-to–left atrial anastomosis made. The site of connection into the superior vena cava is then easily closed from within the right atrium, using a pericardial patch. The right atrium is then closed, rewarming begun, and the remainder of the operation completed as described for patients with connection to the left brachiocephalic vein.

Total Anomalous Pulmonary Venous Connection to Coronary Sinus

The right atrial approach described in the preceding text is used. The right atrium is opened by the usual oblique incision. The repair most commonly used includes excising both the roof of the coronary sinus, so that it communicates freely with the left atrium, and the fossa ovalis ( Fig. 31-12, A-B ). The resulting large defect, made up of a confluence between the rim of the fossa ovalis and the coronary sinus ostium, is then closed with a pericardial patch (Fig. 32-12, C ).

However, occurrence of stenosis at the repair site late after operation has prompted use of the technique described by Van Praagh and colleagues. The foramen ovale is enlarged to obtain an adequate exposure within the left atrium ( Fig. 31-13, A ). The wall between the coronary sinus and left atrium is incised ( Fig. 31-13, B ), and the incision is enlarged as much as possible in both directions. The foramen ovale and coronary sinus ostium are closed separately ( Fig. 31-13, C ). The pulmonary veins then drain into the left atrium through the surgically unroofed coronary sinus ( Fig. 31-13, D ). The remainder of the operation is completed as described for other types of TAPVC.

Obstructed pulmonary venous drainage can occur in patients with TAPVC to the coronary sinus. Thus, the surgeon must be prepared to abandon usual approaches if a stenosis is proximal to the coronary sinus itself, and proceed to anastomose the common pulmonary venous sinus, which is actually the junction of the right and left pulmonary veins, to the back of the left atrium.

Total Anomalous Pulmonary Venous Connection to Right Atrium

Initial stages of the operation are as described for other types of TAPVC using the right atrial approach. The right atrium is opened obliquely. The anomalous connection into the right atrium is explored with an instrument to verify the presence of a confluent pulmonary venous sinus. The foramen ovale is then enlarged, and working through it, an incision is made in the posterior left atrial wall. The common pulmonary venous sinus is visualized through this incision, and the anterior wall of the sinus is incised. This opening is enlarged and anastomosed to the left atrial incision, still working from within the atria. The enlarged foramen ovale is closed by direct suture. The original connection of the common pulmonary venous sinus to the right atrium is closed with a relatively small pericardial patch; it must be remembered that the pulmonary venous pathway from the right lung is beneath the patch.

Alternatively, as described for the repair of TAPVC to the superior vena cava, the common pulmonary venous sinus can be detached from the right atrium, the opening in the sinus enlarged and used for anastomosis to the left atrium, and the resulting defect in the posterior atrial wall closed. The remainder of the operation is completed as usual.

Total Anomalous Pulmonary Venous Connection to Infradiaphragmatic Vein

In TAPVC to an infradiaphragmatic vein, the distal (inferior) portion of the common pulmonary venous sinus is vertical, and proximally (superiorly) it forms a Y or T connection with the left and right pulmonary veins. Therefore, after initial stages of the operation have been performed as described for other types of TAPVC, a decision is made about the approach, which may be similar to that for other types, through the opened right atrium, or through the back of the left atrium directly after tilting the apex of the heart up and to the right. Good results have been obtained by all approaches. The approach using retraction of the cardiac mass out of the pericardial sac is described. The heart is freed from its posterior attachments and the back of the left atrium exposed ( Fig. 31-14, A ). The common pulmonary venous sinus and left atrium are incised ( Fig. 31-14, B ). The common pulmonary venous sinus is anastomosed to the back of the left atrium ( Fig. 31-14, C ) and is ligated ( Fig. 31-14, D ) and may be divided to allow the anastomosis to conform better.