Opposing Mitral Valve Clefts, or Perhaps an Isolated Quadricuspid Mitral Valve: A Case Report.

A quadricuspid mitral valve is an uncommon congenital anomaly whose imaging features are inconsistently reported. Prior case reports frequently describe this finding in patients with hypertrophic cardiomyopathy (HCM), complicating characterization of this anomaly as an isolated finding. We report a 64-year-old male with severe mitral regurgitation of incompletely defined origin and atrial fibrillation presenting for robotic thoracoscopic mitral valve repair and a Cox-Maze III procedure. Intraoperative transesophageal echocardiography demonstrated a thickened, myxomatous mitral valve with deep fissures in both the anterior and posterior leaflets extending to the mitral annulus, with the anterior defect being the predominant origin of regurgitation. The opposing mitral valve defects created four apparent leaflet segments, which were suspicious for a quadricuspid mitral valve but ultimately described as a quadricuspid-appearing mitral valve created by opposing true clefts in the anterior and posterior leaflets. No HCM or other structural cardiac anomalies were identified. Surgical repair included direct closure of the anterior leaflet defect, release of two anterior chordae, and placement of a 38-mm annuloplasty band. Post-bypass imaging showed only trivial residual mitral regurgitation. This case highlights the value of three-dimensional transesophageal echocardiography for defining complex mitral leaflet morphology and its importance in surgical planning.