Morphologic features of foss ovalis membrane aneurysm in the adult and its clinical significance

Objectives. This study evaluated morphologic features of foss ovalis membrane aneurysm and associated cardiac abnormalities that may predispose to systemic embolism. Background. An increasing number of foss ovalis membrane aneurysms are diagnosed by echocardiography. Higher frequencies of such aneurysms have been reported in patients with embolic stroke. Methods. The hearts of 20 adults with foss ovalis membrane aneurysms (mean [±SD] age 62 ± 19 years, range 24 to 87; 12 women [60%], 8 men [40%]) were examined. The areas of excised atrial septum, foss ovalis membrane and foss ovalis were measured. An aneurysm was defined as the ratio of the foss ovalis membrane to foss ovalis are ≥1.5. Results. Compared with control group of 20 adults (mean age 58 ± 21 years, range 18 to 86; 12 women [60%], 8 men [40%]), the 20 patients with foss ovalis membrane aneurysm had larger (711 ± 240 vs. 203 ± 105 mm2, p < 0.0001) and thinner foss ovalis membranes (0.6 ± 0.1 vs. 1.9 ± 0.9 mm2, p < 0.0001). The mean ratio of the foss ovalis membrane to foss ovalis are was 2.1 ± 0.4 in patients with and 1.2 ± 0.1 in those without foss ovalis membrane aneurysm. Patent foramen ovale was seen in 14 (70%) of 20 patients with foss ovalis membrane aneurysm and in 4 (20%) of 20 control subjects (p = 0.0005). Conclusions. Foss ovalis membrane aneurysm is characterized by thinning and marked redundancy without adherent thrombi or fibrin tags. Mitral valve prolapse, dilated atria, intracardiac thrombi and patent foramen ovale are frequently seen in association with foss ovalis membrane aneurysm and may explain the increased frequency of embolic stroke in patients with such aneurysms.