MORPHOLOGIC FEATURES OF FOSSA OVALIS MEMBRANE ANEURYSM IN THE ADULT AND ITS CLINICAL-SIGNIFICANCE

Objectives. This study evaluated morphologic features of fossa ovalis membrane aneurysm and associated cardiac abnormalities that may predis pose to systemic embolism. Background. An increasing number of fossa o valis membrane aneurysms are diagnosed by echocardiography. Higher fre quencies of such aneurysms have been reported in patients with embolic stroke. Methods. The hearts of 20 adults with fossa ovalis membrane a neurysms (mean [+/-SD] age 62 +/- 19 years, rang 24 to 87; 12 women [6 0%], 8 men [40%]) were examined. The areas of excised atrial septum, f ossa ovalis membrane and fossa ovalis were measured. An aneurysm was d efined as the ratio of the fossa ovalis membrane to fossa ovalis area greater than or equal to 1.5. Results. Compared with a control group o f 20 adults (mean age 58 +/- 21 years, range 18 to 86; 12 women [60%], 8 men [40%]), the 20 patients with fossa ovalis membrane aneurysm had larger (711 +/- 240 vs. 203 +/- 105 mm(2), p < 0.0001) and thinner fo ssa ovalis membranes (0.6 +/- 0.1 vs. 1.9 +/- 0.9 mm(2), p < 0.0001). The mean ratio of the fossa ovalis membrane to fossa ovalis area,vas 2 .1 +/- 0.4 in patients,vith and 1.2 +/- 0.1 in those without fossa ova lis membrane aneurysm. Patent foramen ovale,vas seen in 14 (70%) of 20 patients with fossa ovalis membrane aneurysm and in 4 (20%) of 20 con trol subjects (p = 0.0005). Conclusions. Fossa ovalis membrane aneurys m is characterized by thinning and marked redundancy without adherent thrombi or fibrin tags. Mitral valve prolapse, dilated atria, intracar diac thrombi and patent foramen ovale are frequently seen in associati on with fossa ovalis membrane aneurysm and may explain the increased f requency of embolic stroke in patients with such aneurysms.