Pulmonary Atresia With Ventricular Septal Defect

Pulmonary atresia with ventricular septal defect (PA-VSD) is a cyanotic congenital heart disease characterized by underdevelopment of the right ventricular (RV) outflow tract (ie, subpulmonary infundibulum) with atresia of the pulmonary valve, a large ventricular septal defect (VSD), and overriding of the aorta. In the past, this anomaly was termed pseudotruncus or truncus arterious type 4.

Pulmonary atresia with ventricular septal defect demonstrates a wide spectrum of severity, depending on the degree of pulmonary artery development. Pathologically, pulmonary atresia with ventricular septal defect is frequently considered the most severe end of the spectrum of tetralogy of Fallot (TOF), but whether pulmonary atresia with ventricular septal defect and TOF should be treated as 2 distinct entities is controversial. In patients with the standard type of TOF with pulmonary atresia, pulmonary arteries are usually normal in size with normal peripheral pulmonary arborization, which is unlike pulmonary atresia with ventricular septal defect. In addition, systemic-to-pulmonary collateral vessels are not as well developed in patients with TOF with pulmonary atresia as they are in patients with pulmonary atresia with ventricular septal defect.

Frequency

The best estimates of the relative frequency of pulmonary atresia with ventricular septal defect are 2.5-3.4% of all congenital cardiac malformations with a prevalence of 0.07 per 1000 live births. ^{[2, 3]} Pulmonary atresia with ventricular septal defect is slightly more prevalent in males than in females.

Genetic factors are considered to be a contributing factor in that there is an increased risk of occurrence in siblings (2.5%-3%) and in offsprings of adults with tetralogy of Fallot (1.2%-8.3%). ^[4] Associated syndromes include VATER syndrome (ie, vertebral anomalies, anal atresia, tracheoesophageal fistula, esophageal atresia, and renal anomalies), Alagille syndrome, DiGeorge syndrome (velocardiofacial syndrome), and trisomy 21. Tracheobroncial anomalies may be seen as well.

In pulmonary atresia with ventricular septal defect, the extent of pulmonary artery development determines the clinical presentation and the surgical options available. Pulmonary artery atresia may be local only, with involvement of the pulmonary valve and the proximal portion of the pulmonary trunk, or it may involve a longer segment. The right and left pulmonary arteries may communicate freely (ie, confluence) or may not communicate (ie, nonconfluence). Pulmonary circulation may be supplied by a patent ductus arteriosus (PDA), systemic-to-pulmonary collaterals, or plexuses of bronchial and pleural arteries.

The pathology of intrapulmonary arteries depends on the pulmonary blood flow and the patency of the ductus. If the ductus is large and supplies confluent pulmonary arteries, the blood flow and the intrapulmonary arteries of both lungs are normal. If collaterals are multiple and the ductus is congenitally absent, abnormal intrapulmonary arborization (ie, stenosis of unbranched and intrapulmonary arteries) and pulmonary hypertension are present.

Collateral arteries most commonly arise from the thoracic aorta and less commonly arise from subclavian arteries, internal mammary arteries, intercostal arteries, or the abdominal aorta. Rarely, the collateral arteries arise from coronary arteries. In 60% of patients, the collateral arteries are stenosed at the aortic end or at intrapulmonary sites, and stenosis tends to progress over time.

The ventricular septal defect may be membranous or infundibular, is usually very large, and rarely is obstructed by membranous tissue. In 50% of patients, a secundum-type atrial septal defect (ASD) or a patent foramen ovale (PFO) is also present.

The RV and, to a lesser extent, the right atrium usually are moderately to markedly hypertrophied and dilated. The left atrium and left ventricle (LV) are usually normal. The coronary arteries are usually normal, although anomalies have been observed, such as a high origin of the coronary ostia, coronary artery–to–pulmonary artery fistulae, ^[5] and transposition anatomy with the right coronary artery originating from the left anterior aortic sinus and transversing the right ventricular infundibulum. Other associations include tricuspid atresia or stenosis, complete atrioventricular (AV) canal, complete or corrected transposition of the great arteries, left superior vena cava, anomalies of the coronary sinus, dextrocardia, and asplenia or polysplenia syndrome.

Classification

See the list below:

• Type A: Pulmonary blood flow is provided by native pulmonary arteries. Patency of the ductus maintains pulmonary circulation.
• Type B: Pulmonary blood flow is supplied by native pulmonary arteries and by major aortopulmonary collateral arteries. The native pulmonary arteries may be supplied by either a ductus and/or major aortopulmonary collateral arteries (MAPCAs)
• Type C: Pulmonary blood flow is provided by major aortopulmonary collateral arteries. Native pulmonary arteries are absent.

Children born with pulmonary atresia and ventricular septal defect (PA-VSD) may have unpredictable presentations owing to the variability of the lesion.

The age at presentation may vary depending on the amount of pulmonary blood flow. However, the great majority of patients present in the newborn period after the closure of the ductus arteriosus. Late presentation may rarely occur, and findings may include polycythemia, clubbing, cerebral embolisms, and cerebral abscesses.

The vast majority of patients present in infancy with cyanosis and hypoxia. The degree of cyanosis depends on whether the ductus is patent and how extensive the systemic collateral arteries are. Rarely, an infant with a large PDA or well-developed systemic collateral arteries may present at age 4-6 weeks with heart failure symptoms secondary to increased pulmonary blood flow. This heart failure may be very difficult to control medically. Paroxysms of dyspnea and squatting occasionally occur in older children.

Hemoptysis may occur as a result of rupture of extensive systemic-to-pulmonary collateral arteries. Important and recurrent infections can occur because of immunodeficiency, especially if associated with DiGeorge syndrome. Survival to adulthood has been described in a few patients with well-developed collateral arteries.

Growth and development are usually delayed secondary to cyanosis or congestive heart failure (CHF).

Central (ie, perioral) cyanosis is usually mild at birth, but it becomes very severe with the closure of the PDA. Cyanosis may fluctuate for the first few days because the ductus arteriosus may constrict and relax intermittently. The patient may have anomalies of the face, palate, and ears as described in velocardiofacial syndrome. Peripheral pulses are usually normal in neonates and remain normal in cyanotic infants. In infants with wide-open PDAs, well-developed systemic collateral arteries, or surgically created shunts, pulses may become pronounced after 4-6 weeks because of a wide pulse pressure.

The following may be observed on auscultation:

• S ₁ is normal; S ₂ (ie, aortic valve closure) is always single and often accentuated. A grade 3/6 systolic murmur usually is audible along the lower left sternal border.
• A continuous murmur is best heard over the upper chest in the presence of a PDA.
• If systemic-to-pulmonary collateral arteries are present, continuous murmurs may be diffusely audible over the entire chest and back.
• In some patients with severe cyanosis, no murmur can be heard.
• An early diastolic murmur of aortic regurgitation may be noted.

Features of pulmonary atresia with ventricular septal defect

Distinguishing characteristics for the diagnosis of pulmonary atresia with ventricular septal defect can be divided into 2 major groups, as summarized below.

Decreased pulmonary blood flow in a neonate with cyanosis

Associated defects may include the following:

• Severe tetralogy of Fallot
• Transposition of the great arteries with pulmonary stenosis
• Tricuspid atresia
• A double-outlet RV with severe pulmonary stenosis
• A single ventricle with severe pulmonary stenosis
• Total anomalous pulmonary venous connection with pulmonary venous obstruction

Normal or increased pulmonary blood flow in a neonate with minimal cyanosis with or without heart failure

Associated defects may include the following:

• Ventricular septal defect
• PDA
• AV canal defect
• A double-outlet RV without significant pulmonary stenosis
• A single ventricle without significant pulmonary stenosis
• Persistent truncus arteriosus
• Total anomalous pulmonary venous connection without pulmonary venous obstruction

Consult a pediatric cardiologist, a pediatric cardiothoracic surgeon, and a geneticist.

Criteria for complete surgical repair of pulmonary atresia with ventricular septal defect (PA-VSD) are as follows:

• The native pulmonary arteries provide all or most pulmonary blood flow with oxygen saturations more than 75%.
• The native pulmonary arteries must supply at least 10 segments, the equivalent of one lung.
• If additional major collaterals are identified, test the level of arterial oxygen saturation after occlusion of the collaterals in the catheterization laboratory. If the oxygen saturation remains greater than 75%, then coil occlusion of the collaterals is carried out.
• The Nakata index is used to guide decision making for surgical repair. it is defined as the cross-sectional area (in mm ²) of the left and right pulmonary arteries just before the lobar branches, divided by the total body surface area (BSA). Good candidates for complete repair are those with a Nakata index above 200 mm ²/BSA.

Contraindications for complete surgical repair of pulmonary atresia with ventricular septal defect include (1) hypoplastic or absent central pulmonary arteries and (2) inadequate peripheral arborization of pulmonary arteries.