[Pseudotumor of the right atrium caused by hernia of the valve of Vieussens].

A round swelling was on the substraction films of the right side of the heart taken during angiocardiographic examination of a patient with mitral valve disease; this suggested a mass attached to the inter-atrial septum, and prolapsing into the auricle of the right atrium. Initial diagnsosi was of atrial thrombosis, but this was disproved at operation. An aneurysm of the membrane of the fossa ovalis was found, being caused by overstretching of the auricle of the left atrium under the increased pressure of the valve defect. The aneurysm was resected and the septum simply repositioned as part of the mitral valve replacement. A search of the literature shows how rare this disorder is, and that it should be reclassified with the abnormalities of the inter-atrial septum which are found only rarely in cases of mitral valve disease.