Aneurysm of the membraous septum in ventricular septal defect.

An aneurysm of the membranous septum was found frequently in patients with ventricular septal defect; although appearance at catheterization during infancy was not common, aneurysms were detected in about half of the patients older than 2 years of age. A significant decrease in the left-to-right shunt occurred with the development of an aneurysm, but progression to complete spontaneous closure was not seen in any patient. In three older patients, an aneurysm of the membranous septum "disappeared" with time, even though complete spontaneous closure had not occurred.