Resolving the Disproportionate Left Ventricular Enlargement in Mitral Valve Prolapse Due to Barlow Disease

Objectives This study hypothesized that left ventricular (LV) enlargement in Barlow disease can be explained by accounting for the total volume load that consists of transvalvular mitral regurgitation (MR) and the prolapse volume. Background Barlow disease is characterized by long prolapsing mitral leaflets that can harbor a significant amount of blood—the prolapse volume—at end-systole. The LV in Barlow disease can be disproportionately enlarged relative to MR severity, leading to speculation of Barlow cardiomyopathy. Methods Cardiac magnetic resonance (CMR) was used to compare MR, prolapse volume, and heart chambers remodeling in patients with Barlow disease (bileaflet prolapse [BLP]) and in single leaflet prolapse (SLP). Results A total of 157 patients (81 with BLP, 76 with SLP) were included. Patients with SLP were older and more had hypertension. Patients with BLP had more heart failure. Indexed LV end-diastolic volume was larger in BLP despite similar transvalvular MR. However, the prolapse volume was larger in BLP, which led to larger total volume load compared with SLP. Increasing tertiles of prolapse volume and MR both led to an incremental increase in LV end-diastolic volume in BLP. Using the total volume load improved the correlation with indexed LV end-diastolic volume in the BLP group, which closely matched that of SLP. A multivariable model that incorporated the prolapse volume explained left heart chamber enlargement better than a MR-based model, independent of prolapse category. Conclusions The prolapse volume is part of the total volume load exerted on the LV during the cardiac cycle and could help explain the disproportionate LV enlargement relative to MR severity noted in Barlow disease.