First, to examine the morphology of heart specimens with defects of the oval fossa so as to define the factors that facilitate appropriate selection of the size of devices used for inteventional closure. Second, to examine the relationship between morphology and transthoracic and transesophageal echocardiography.

The success of transcatheter closure is influenced by the variable morphology of deficiencies with the oval fossa, and of the relationship of the fossa itself to adjacent structures. More appropriate selection could reduce the incidence of failures.

From over 100 specimens in the cardiac registry at the University of California, San Francisco, we judged 16 hearts with atrial septal defects within the oval fossa, either in isolation or associated with other cardiac malformation, to be suitable for this study. We measured the dimensions of the defect and the surrounding rims of the fossa. All values were normalized to the diameter of the aortic root.

A fenestrated defect was present in 9 specimens (56%). The shape defect itself was oval in all specimens, with a ratio of major to minor axes of 1.70 ± 0.63– The major axis took one of three main directions with respect to the vertical plane: in 11 specimens (69%) it was at horizontal; in 3 (19%) it was at oblique at an angle of 45 degrees; and in 2 (12%) it was vertical. Discordance was noted in some hearts between the major axis of the defect and that of the oval fossa. Structures closest to the rim of the fossa were the aortic mound, the coronary sinus, and the hinge point of the aortic leaflet of the mitral valve.

Extrapolating from these specimens permitted identification of the major and minor axes of the atrial septal defect by transthoracic and transesophageal echocardiography. Our study has identified landmarks and dimensions that may be employed to improve effectiveness of selection of patients for transcatheter closure of defects within the oval fossa.