Spontaneous closure of the ventricular component of an atrioventricular septal defect

It is well recognized that perimembranous ventricular septal defects close or diminish in size spontaneously due to the development of fibrous tissue tags, which are usually termed "aneurysms of the membranous septum." Morphologic examination, however, has shown conclusively that they are almost always derived from the leaflets of the tricuspid valve.¹ Equally well described, although certainly less well recognized, are the "aneurysmal-like" structures that may be derived from the bridging leaflets in the setting of an atrioventricular (AV) septal defect. The angiomorphologic correlation study of Kudo et al² established the frequent existence of such pouches in the setting of so-called "ostium primum" defects, but suggested that they did not exist with common AV valve orifice. We now report a patient with AV septal defect and common orifice in whom ventricular shunting was virtually abolished concomitant with the development of pouches from the bridging leaflets that blocked the septal defect. This report illustrates the angiographic findings in this patient together with the morphologic features of a heart specimen exhibiting a similar malformation.