Pulmonary Atresia with Intact Ventricular Septum

PA-IVS is a group of cardiac malformations having in common absent communication between the right ventricle and the pulmonary arterial circulation (pulmonary atresia) in combination with an intact interventricular septum (Fig. 24.12). The pulmonary atresia is usually of the membranous type with complete fusion of the valve commissures and a normally developed infundibulum. On occasion, however, the pulmonary atresia is muscular with a severely distorted right ventricular outflow tract region. The right ventricular cavity is either hypoplastic with thickened right ventricular myocardium (Fig. 24.12) or dilated with significant tricuspid valve regurgitation and a dilated right atrium (see Chapter 20). A hypoplastic right ventricle occurs in the majority of cases (5). The size of the right ventricular cavity correlates with the Z-score of the diameter of the tricuspid valve (11, 12). One of the major associated findings in hearts with PA-IVS and hypoplastic right ventricles is an anomaly of the coronary circulation, namely, ventriculocoronary arterial communication (VCAC) (Fig. 24.12B), found in about one-third of cases of PA-IVS. Systemic collateral arteries to the lungs, which are typical for pulmonary atresia with ventricular septal defect (see Chapter 25), are not found in PA-IVS.