High-resolution analysis with multiphase computed tomography of the left atrio-ventricular junction in mitral annular disjunction

Abstract

Abstract Background Mitral annular disjunction (MAD) has been associated with myxomatous mitral valve disease (MMVD) but functional analyses of the mitral annulus (MA) and the entire left atrio-ventricular junction (LAVJ) are lacking from high-resolution imaging to understand MAD physiopathology. Purpose Using multiphase cardiac computed tomography imaging (4D-MCCTI), we aimed at characterizing the morphological changes of MA and LAVJ throughout the cardiac cycle. Methods Volume imaging data sets through time were obtained from 4D-MCCTI of 2 groups of 10 patients as defined by echocardiographic diagnosis of MMVD and/or MAD: MMVD+MAD+, MMVD+MAD− and 20 case-controls without mitral regurgitation (MMVD−). Data were implemented in a custom software for 3D semi-automated delineation of 18 points around MA perimeter. Coordinates of these points in each of the 10 time-phases within an RR interval were used for MA reconstruction and calculation of areas, perimeters, 360°-diameters and parameters of planar/vertical deformation. Subsequently, left ventricle (LV) and left atrium (LA) inner contours were delineated. Results Groups were similar for age, body surface area and LV ejection fraction. Compared to the 2 other groups, MA expansion in MMVD+MAD+ started early after end-diastole, following LA expansion, and reached a maximum at end-systole (ES): 3D-area ES: 13.9±4.0cm2/m2, 3D-perimeterE S: 10.4±1.6cm/m2 versus respectively 8.8±3.0cm2/m2, 7.9±1.4cm/m2 in MMVD+MAD− (p<0.001) and 6.1±1.3cm2/m2, 7.0±1.1cm/m2 in MVVD− (p<0.001). However throughout the cardiac cycle, MA perimeter reduction was not altered in MMVD+MAD+: −14.0±6.3%, compared to MMVD+MAD−: −10.1±5.6% and MMVD−: −8.7±2.3% (p=0.09). MA shape modification was different in MMVD+MAD+ group, MA becoming more elliptical during systole, whereas MA reached a minimal eccentricity index (EcI) at ES in both MMVD+MAD− and MMVD− groups: EcIES = 0.63±0.09 versus 0.52±0.15 and 0.49±0.13 (p=0.04), respectively (Figure). Surprisingly, vertical deformation of MA increased during early systole in MMVD+MAD+ group when MA became more planar in the MMVD+MAD− and MMVD− groups. Conclusions MA function was globally preserved in MAD but was desynchronized with respect to LV contraction. Eccentricity index of mitral annulus Funding Acknowledgement Type of funding source: None