The Unnatural History of the Left Ventricle After Double Switch Operation for Congenitally Corrected Transposition of the Great Arteries with Intact Ventricular Septum: Dilation is the Norm.

Double Switch Operation (DSO) for congenitally-corrected transposition of the great arteries/intact ventricular septum (ccTGA/IVS) restores the morphologic left ventricle (LV) to the systemic position. While outcomes have been studied using the LV ejection fraction (EF) as a metric, little is known about LV volumetric remodeling over time. This retrospective single-center study describes the volumetric evolution of the LV from 302 echocardiograms in 70 patients with ccTGA/IVS who underwent DSO. Echocardiographic measurements of LV end-diastolic volume (EDV) and end-systolic volume (ESV) Z-scores, mass, and EF were recorded. Cubic spline modeling was used to evaluate temporal trends in volumetric parameters. LV EDV and ESV Z-scores rose acutely post-DSO and continued to rise until ~ 4 years post-DSO. LVEF declined slightly acutely post-DSO (pre-DSO 54% [46, 62], discharge study 48% [38, 54], p < 0.001) and then stabilized. LV mass increased, but mass-to-volume ratio declined over time, consistent with eccentric hypertrophy. Univariate analysis showed that any neo-aortic regurgitation at discharge was associated with increased dilation (EDV Z-score change + 1.08, p = 0.002). Lower pre-DSO LV: RV pressure ratio was associated with the greatest acute dilation (top 10th percentile Z-score change from pre-DSO to discharge, OR 1.65 per 0.1-unit decrease, p = 0.033), though this association did not hold when using a top 20th percentile Z-score change cut-point. The LV in ccTGA/IVS patients undergoes acute and sustained dilation and eccentric hypertrophy after DSO. Neo-aortic regurgitation and lower pre-DSO LV: RV pressure ratio may be associated with dilation. Multi-center outcome studies are warranted to determine the clinical implications of this remodeling.