PULMONARY ATRESIA, INTACT VENTRICULAR SEPTUM, AND AORTOPULMONARY COLLATERAL ARTERIES

In muscular pulmonary atresia, major aortopulmonary collateral arterie s are characteristic of pulmonary atresia with ventricular septal defe ct and are rarely seen in pulmonary atresia with intact ventricular se ptum. Two unusual cases of muscular pulmonary atresia are reported, on e with an intact septum and one with a perimembranous ventricular sept al defect, closed in utero by aneurysmal tricuspid tissue. In both cas es the pulmonary blood supply came entirely from aortopulmonary collat erals. In case 1 a collateral artery connected the left subclavian art ery and hypoplastic pulmonary arteries, and several aortopulmonary col laterals arose from the descending aorta, without overlap between thes e two circulations. In case 2 the pulmonary trunk and arterial duct we re absent and the pulmonary blood supply came entirely from collateral arteries. The right ventricle was of normal size and tripartite with a closed perimembranous ventricular septal defect, discovered only at postmortem examination. These observations suggest right ventricular o utflow tract obstruction early in fetal development, with involution o f the pulmonary trunk and sixth arch derivatives, and persistence of p rimitive aortopulmonary connections. The morphology in case 1 is at od ds with the theoretical division of pulmonary atresia with intact sept um and pulmonary atresia with ventricular septal defect into two separ ate pathological entities that occur at different stages in fetal deve lopment.