Isolated Congenital Membranous Interventricular Septal Aneurysm: A Rare Incidental Finding

Membranous interventricular septal aneurysm (MVSA) is a rare congenital cardiac anomaly, typically associated with interventricular septal defects. Isolated MVSAs are even more uncommon and often discovered incidentally. While generally asymptomatic, MVSAs carry the potential for significant complications, warranting thorough evaluation and follow-up. We present the case of a 30-year-old physician with no personal or family history of cardiovascular disease, who was referred to our department following the incidental discovery of a cardiac abnormality during a transthoracic echocardiography workshop. The patient was asymptomatic, with a normal physical examination and electrocardiogram. Echocardiography revealed a 21 × 19 mm membranous interventricular septal aneurysm protruding into the right heart chambers, with no evidence of interventricular shunting, right ventricular outflow obstruction, aortic regurgitation, or vegetation. A 24-hour Holter ECG showed no arrhythmias. A conservative management strategy was adopted after a multidisciplinary discussion. The patient was informed of the potential risks, advised to avoid strenuous isometric activities, and scheduled for echocardiographic follow-up every six months during the first year, then annually. At 12-month follow-up, the patient remained asymptomatic with stable findings. This case emphasizes the importance of recognizing and evaluating isolated MVSAs, even in asymptomatic individuals, due to their potential for serious complications.