High-Resolution Analysis With Multiphase Computed Tomography of the Left Atrio-Ventricular Junction in Mitral Annular Disjunction

Objective Among myxomatous mitral valve disease (MMVD), mitral annular disjunction (MAD) is associated with severe mitral regurgitation (MR). However, functional analyses are lacking to fully understand the mechanisms leading to bileaflet prolapse in MAD. Using multiphase cardiac computed tomography imaging (4D-MCCTI), we aim to characterize left atrio-ventricular junction morphological alterations throughout the cardiac cycle in patients with MAD. Methods Imaging datasets were obtained via 4D-MCCTI for 2 groups of consecutive patients with severe MR due to MMVD: 22 with MAD (MMVD + MAD+) and 20 without (MMVD + MAD−). A control group of 30 patients (MMVD−) was also included. Semi-automated delineation of 18 points around the mitral annulus (MA) allowed 3D calculation of areas, perimeters, 360°-diameters, and planar/vertical deformation across time. Left ventricular (LV) and atrial (LA) inner contours were also delineated, and systolic shortening distances from the annulus to the anterior and posterior papillary muscles (MA-APM and MA-PPM) were estimated. Results Groups were comparable for age, pulmonary pressures, and LV ejection fraction. In MMVD + MAD+, MA expansion began earlier in systole, following LA expansion, and peaking at end-systole: 3D-area: 10.9±3.7cm 2 /m 2 , compared to 8.9±2.4 cm 2 /m 2 for MMVD + MAD− ( P < .001) and 6.1±1.3 cm 2 /m 2 for MMVD− ( P < .001). However, MA perimeter reduction remained unaltered in MMVD + MAD + patients (−14.7±5.2%). In systole, MA-APM and MA-PPM reduction were greater in MMVD + MAD+: −6.58±1.99 mm, −8.12±1.26 mm versus −2.53±2.01 mm, −3.25±2.31 mm in MMVD− and −2.18±1.79 mm, −3.86±2.77 mm in MMVD + MAD− ( P < .001). Conclusions In MAD, MA becomes desynchronized from LV function. The extent of systolic MA deformation and papillary muscle movement may promote bileaflet prolapse.