747-5 Transesophageal Echocardiographic Quantitation of Mitral Leaflet Thickness in Patients with Mitral Valve Prolapse

Abstract

Mitral leaflets which appear abnormally thick by transthoracic echo predict an adverse prognosis in pts with mitral valve prolapse (MVP). While it is known from pathologic studies that the valve tissue in such pts is both redundant and abnormally thick, the echocardiographic appearance of increased thickness may result from a combination of overlap of redundant tissue and intrinsic increases in leaflet thickness. Transesophageal echo (TEE) affords the opportunity to more precisely characterize the morphology of the mitral leaflets in these patients. Accordingly, twenty-two pts [11 with MVP (defined as superior displacement of the mitral leaflets above the mitral annulus on the parasternal long axis view of the transthoracic echo and increased diastolic width of the anterior mitral leaflet) and 11 controls (CTRL)] prospectively underwent detailed TEE examination to quantify mitral leaflet thickness. Since systolic tensing of the closed mitral leaflets minimizes tissue overlap, systolic leaflet width was used to measure intrinsic tissue thickness. In contrast, the width of the relatively slack mitral leaflets in diastole represents a combination of both leaflet overlap and intrinsic tissue thickness. Blinded TEE measurements of leaflet width demonstrated greater diastolic width of both anterior (0.64 ± 0.20 v. 0.30 ± 0.04 em, p < 0.001) and posterior (0.67 ± 0.39 v. 0.31 ± 0.06 em, p < 0.01) leaflets in MVP compared to CTRL. In contrast systolic width of the anterior (0,22 ± 0.05 v, 0.20 ± 0.04 em, NS) and posterior (0.25 ± 0.07 v. 0.24 ± 0.05 em, NS) leaflets were similar in MVP and CTRL. Fractional change in leaflet width from diastole to systole (%ΔW = [(diastolic width) - (systolic Width)] × 100/[diastolic width]) was measured as an index of the change in leaflet overlap between diastole and systole, %LΔW was significantly greater for both anterior (62 ± 13 v. 34 ± 16%, p < 0.001) and posterior (54 ± 19 v. 22 ± 21%, p < 0.005) leaflets in MVP compared to CTRL. In MVP the echocardiographic appearance of increased diastolic mitral leaflet thickness is largely due to tissue overlap of the redundant leaflets, while they are relatively slack. By contrast under systolic tensioning, which minimizes tissue overlap, the leaflet thickness appears similar in MVP pts and CTRL.