152 Towards a Noninvasive Assessment of Valve Biology: Echocardiographic Measures of Mitral Leaflet Distensibility

Abstract

Changes in mitral valve (MV) elasticity or distensibility occur in disease and directly affect MV function, contributing to MV prolapse (MVP) or flail vs restricted coaptation of stiffer leaflets in functional mitral regurgitation (FMR) and MV stenosis (MS). Recent studies suggest MV distensibility may be modified to reduce MR, but distensibility has only been measured in excised MVs. Our aim was to test the feasibility of obtaining a noninvasive measure of MV distensibility in patients by measuring systolic change in anterior leaflet length (ALL) or anterior leaflet strain; and to test the hypothesis that these measures vary in diseases with known altered MV elasticity. ALL was quantified in a long-axis view standardized by 3D echo in 80 patients: 20 each with normal hearts, MVP, FMR and MS. Distensibility was measured as end-systolic (ES) – end-diastolic (ED) total ALL normalized to an ED reference; and alternatively as mid-leaflet strain measured by tracking echo features. ALL was greater in all disease groups vs normal (p<.001). The maximum systolic increase in ALL relative to ED was 7.9 ± 7.4% in normals vs >2-fold higher (17.6 ± 11.2%) in MVP; it was 63-76% lower (2.9 ± 3.0%, 1.9 ± 3.1%) in FMR and MS, with comparable results for segmental AL strain (Table). Noninvasive echocardiographic measures of MV distensibility based on systolic changes in total length or segmental strain are feasible. Results are consistent with excised valve biomechanics, showing increased distensibility in MVP and decreased values in FMR and MS. Ultimately, these techniques have the potential to monitor response to new therapies that aim to improve MV biology and mechanics to reduce MR.ParameterunitNormMVPFMRMSALL systolemm.26.6 ± 2.739.7 ± 5.6*32.7 ± 4.1*33.4 ± 5.0*ALL diastolemm.24.5 ± 3.133.5 ± 3.2*32.0 ± 4.2*32.8 ± 4.9*ALL (sys-dia)/dia%7.9 ± 7.417.6 ± 11.2*2.9 ± 3.0*1.9 ± 3.1*SegL (ES-ED)/ED%9.1 ± 4.819.6 ± 10.9*3.2 ± 2.6*2.7 ± 3.7**P < 0.05 vs. Normals P < 0.05 vs. Normals