An Unreported Congenital Anomaly: Aneurysm of the Lateral Half of the Mitral Valve.

This case draws our attention to a new type of mitral valve anomaly, which seems to be congenital. A 42-year-old man with symptomatic primary severe mitral regurgitation was admitted to our hospital. Echocardiography revealed an aneurysm of the half of the valve, on the anterolateral commissure side, with significant excess tissue. The other half of the valve was normal. The two parts seemed to be separated by a continuous fibrous raphe. The anterolateral papillary muscle was hyperplasic and gave the main part of chordae tendinae.