Abstract 15124: Abnormalities in Papillary Muscle and Mitral Valve Independently Predict Left Ventricular Outflow Tract Gradient in Hypertrophic Cardiomyopathy Patients without Overt Septal Hypertrophy: A Multimodality Imaging Study

Abstract

Background: A subset of hypertrophic cardiomyopathy (HCM) patients have left ventricular outflow tract obstruction (LVOTO), without increased basal septal thickness (BST). There is a high proportion of abnormal mitral valve (MV) morphology (long anterior MV leaflet & abnormal chordal attachment) or papillary muscle (PM) abnormalities, resulting in LVOTO. Using echo & cardiac magnetic resonance (CMR), we assessed predictors of LVOTO in HCM patients with significant LV hypertrophy.

Methods: We studied 121 HCM patients (age 49 ± 17 years, 65 % men, 57 % on betablocker) with BST ≤ 1.8 cm that underwent echo (rest + stress) & CMR. Echo measurements included: maximal LVOT gradient (rest/provocable)], MV length (averaged in parasternal long, 4 & 3-chamber views, Figure 1a) & abnormal cordal attachment, to mid/base of anterior MV (present or absent, Fig 1b). CMR measurements included BST, number & thickness of PM heads & laxity on cine (in systole & diastole, Figure 1c-d).

Results: Mean BST, LVOT gradient & LV ejection fraction were 1.5±0.3 cm, 72±54 mm Hg & 61±6%. Number of anterolateral & posteromedial PM heads were 2.7±0.7 and 2.6±0.7. Anterolateral & posteromedial PM thickness were 1.9±1 cm & 1.8±0.5 cm. PM laxity was 11±6⁰. Predictors of maximal LVOTG are shown in Figure 2. 46 patients underwent surgery to relieve LVOTO, of which 52 % needed additional non-myectomy (MV repair/replacement or PM reorientation) approaches.

Conclusion: In HCM patients without significant LV hypertrophy, anterior MV length, abnormal chordal attachment & PM laxity are independently associated with LVOTO. In such patients, additional procedures on MV & PM (± myectomy), guided by imaging should be considered.