Uni-leaflet mitral valve in adults: a systematic review of case reports and case series

INTRODUCTION: Uni-leaflet mitral valve (ULMV) is a rare congenital anomaly historically considered incompatible with long-term survival, yet increasing reports describe diagnosis in adulthood. We conducted a systematic review to characterize clinical presentation, anatomy, imaging findings, management, and outcomes in adults with ULMV. METHODS: Following PRISMA guidelines, major databases were searched from 1960 through January 2024. Eligible studies reported adult patients with confirmed ULMV. Data were extracted on demographics, valve morphology, symptoms, associated anomalies, imaging modalities, interventions, and outcomes. RESULTS: Thirty-six publications comprising 40 adult patients met inclusion criteria. Mean age at diagnosis was 50.5 years, with female predominance. Posterior leaflet hypoplasia or agenesis accounted for 97.5% of cases. Most patients were symptomatic, commonly with dyspnea or heart failure, and over half had moderate or greater mitral regurgitation. Atrial fibrillation, atrial septal defects, and aortic valve abnormalities were frequent comorbidities. Transthoracic echocardiography was used universally, with transesophageal and three-dimensional imaging providing incremental anatomical detail. Approximately one-third underwent mitral valve repair or replacement, with generally favorable outcomes. CONCLUSIONS: Adult ULMV demonstrates marked clinical and anatomical heterogeneity and may represent a developmental spectrum rather than a single entity. Standardized definitions and prospective registries are needed to improve risk stratification and guide management. PROTOCOL REGISTRATION: http://www.crd.york.ac.uk/prospero identifier is CRD420251083213.