Measurements of the Interventricular Septum and Mitral Leaflet length in Hypertrophic Cardiomyopathy Patients Undergoing Surgical Myectomy: A Prospective Comparative Multimodality Imaging Study

Abstract

Transesophageal echocardiography (TEE) plays an important role for real-time procedural guidance during surgical myectomy (SM) for hypertrophic obstructive cardiomyopathy (HOCM). We aimed to compare a) IVS thickness using two (2D) and three-dimensional (3D) intraoperative TEE and pre-operative cardiac magnetic resonance (CMR) and b) mitral valve (MV) leaflet length using 2D, 3D TEE, automatic quantification of mitral valve (AMVQ) and pre-operative CMR. We prospectively studied 50 HOCM patients (age 59 ±12, 44% men) undergoing SM during 2018-2019. Maximal basal, mid, and distal anteroseptum (AS) and inferoseptum (IS) were measured by multiplanar 3D reconstruction on TEE and by short axis imaging on pre-operative CMR, and classified as mild (≤18mm), moderate (18-25mm) or severe (≥ 25 mm) groups, based on AS and IS thickness on CMR. MV leaflet lengths were evaluated by pre-operative CMR and intra-procedural 2D TEE, zoom 3D TEE and AMVQ (EchoPAC, General Electric, Wi). There was a moderate correlation between AS and IS thickness on 3D TEE and CMR (R2=0.46, p<0.01 and R2=0.41, p<0.01 respectively), with 3D TEE showing an average overestimation of 3.8 and 4.7 mm vs. CMR. 3D TEE over-estimated 14 (56%) patients with mild thickness as moderate, and 5 (22%) patients with moderate thickness as severe. Assuming 3D TEE as the gold standard, the closest correlation for anterior mitral leaflet length was with CMR (average overestimation by CMR of 0.5 mm [root mean square deviation or RMSE% 17]), intermediate correlation with 2D TEE (average deviation of 0.6 mm [RMSE%:21]) and no correlation with AMVQ (average deviation of 0.7mm [RMSE% 24]). In conclusion, 3D TEE overestimates IVS thickness vs. CMR in HOCM patients undergoing SM, with greater discrepancy in those with thinner IVS. There are significant differences in MV lengths measured using different imaging techniques.