Residual mitral leaflet length independently indicates left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

Abstract Background Due to its dynamic character, the diagnosis of left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy (HCM) often requires extensive exercise testing. Mitral valve alterations represent structural parameters that are not affected by load or contractility and influence left ventricular outflow tract (LVOT) gradients. The residual portion of the mitral valve extending past its coaptation (RML) has been postulated as a necessity to exhibit LVOTO. Purpose This study aims to assess the impact of RML length on the likelihood of LVOTO in HCM patients. Methods This is a cross-sectional, multi-center, registry-based analysis conducted at two HCM referral centers. The study included HCM patients with valid standardized transthoracic echocardiographic examinations. Blinded investigators performed post-processing echocardiographic analyses. LVOTO was defined as resting or dynamic peak LVOT gradients ≥30 mmHg. Results Among 270 HCM patients studied (43% women, mean age 58±14 years), 131 patients (49%) exhibited LVOTO, with 76 (28%) having undergone septal reduction therapy (SRT). Patients with obstructive HCM exhibited a more pronounced end-diastolic interventricular septum (IVSd) thickness (2.2±0.4 vs. 1.8±0.5 cm; p