Abstract 12806: Anatomic Correlates of Systolic Anterior Motion in D-looped Transposition of the Great Arteries Post Atrial Switch

Abstract

Introduction: A paucity of data exists of the anatomic-physiological mechanisms for sub-pulmonic systolic anterior motion (SAM) of the mitral valve (MV) in d-looped transposition of the great arteries post atrial switch (d-TGA/AtS). Hypothesis: The development of SAM may be inherent to the anatomy of the MV or affected by external factors such as a dilated systemic right ventricle (RV) or pectus deformity. Methods: Clinical and cardio-imaging analysis of 18 adult patients with d-TGA/AtS (Age 42±6 years old, 56% Male) between 2015-2019 was performed. Echocardiography data included mitral apparatus anatomy (Figure) and CT/MRI data included biventricular dimensions, function, and Haller index (HI). Results: Patients with leaflet SAM (n=5) compared to patients without SAM (n=13) had significantly higher MV protrusion height (2.1 ± 0.4 vs 1.5 ± 0.4 cm p ≤0.01, respectively, Table) and longer anterior MV leaflet length (3.0 ± 0.24 vs 2.6 ± 0.34 cm p ≤0.05, respectively, Table) when compared to those without. CT/MRI showed higher sub-pulmonic left ventricular ejection fraction (LVEF) in the SAM group relative to No SAM (68 ± 5 vs 54 ± 7 % p ≤0.005, respectively, Table). RV size and function, chest deformity (HI>3.5), presence of a ventricular lead pacemaker, and septal thickness did not play a role in development of SAM (Table). Conclusions: An elongated mitral apparatus is associated with the development of SAM in d-TGA/AtS and the development of LVOT obstruction. Increased sub-pulmonic LVEF contributes to SAM, whereas the systemic RV dimensions, septal thickness, and degree of chest deformity do not correlate with SAM.