An aneurysm of the fossa ovalis was identified at autopsy in 17 infants. In each case the aneurysm of the fossa ovalis was considered to have resulted from excessive elevation of pressure in that atrium contralateral to the side into which the aneurysm bulged. The aneurysms were divided into two types: intrinsic (three cases) and extrinsic (14 cases). The intrinsic types of aneurysms of the fossa ovalis were considered to have started in fetal life and were consequences of abnormally narrow states of interatrial ostium II. Each intrinsic aneurysm bulged toward the left. Among the extrinsic types of aneurysm of the fossa ovalis, each was considered to have resulted from the hemodynamic consequences of a congenital anomaly in one side of the heart or other. Six aneurysms of extrinsic type bulged toward the left and eight toward the right. Aneurysm of the fossa ovalis should be included in the differential diagnosis of space-occupying conditions within the atria.

A review of 18 cases with discrete subaortic stenosis (DSS) revealed that involvement of the aortic valve cusps in the basic process was present in 16. In these 16 cases, extensions of fibroelastic tissue from the site of the DSS toward the base or superior to the base of one or more cusps were seen. In seven of the involved cases, deformity of a cusp was associated with these extensions. Valvular aortic insufficiency in cases with DSS might be caused by extensions of the fibroelastic tissue to the aortic cusps.

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