Systolic performance of the single ventricle, exercise capacity, and endothelial function in pediatric Fontan patients

Background By age 40, roughly half of the individuals with Fontan circulation will have died or undergone heart transplantation. Poor exercise capacity and endothelial dysfunction accelerate disease progression. Objective This study aims to assess the systolic function of the single ventricle (SV) in pediatric Fontan patients entering an exercise intervention (RE-ENERGIZE FONTAN) and how it is associated with exercise capacity and endothelial function. Methods This cohort comes from an ongoing randomized trial in Fontan patients, using live video conferencing for supervised exercise. Participants (ages 8-19) cleared for exercise underwent 2D/3D echocardiograms, cardiopulmonary testing, and endothelial function (RHI). 2D longitudinal strain (LS, right ventricle), 2D global longitudinal strain (GLS, left ventricle), and circumferential strain were measured with TomTec, and 3D ejection fraction (3D-EF) and 3D-GLS were calculated. Results We have enrolled 114 Fontan patients. Median age was 12.7 years [IQR 10.2, 15.6]. The median time from Fontan operation was 8.8 years [IQR 6.2, 12.0]. Fifty-seven patients (50%) had a single right ventricle. SV systolic performance measures were: 2D-LS/GLS -15.6±4.19%, circumferential strain was -18.7± 6.83%, 3D-EF 49.9±7.26%, and 3D-GLS -16.8±4.37%. Peak VO 2 was 1290±502 ml/min, and percent predicted peak VO 2 was 67.8±15.6%. RHI was 1.44±0.576. 2D-LS/GLS and 3D EF correlated with percent predicted peak VO 2 (R= -0.28, p=0.007 and R= 0.24, p=0.019). 3D-EF correlated positively with RHI (R= 0.29, p=0.0071). Conclusions In this cohort of pediatric Fontan patients, SV systolic function was diminished at baseline, and there was a direct correlation between 2D strain and 3D-EF with percent predicted peak VO 2, and additionally, 3D-EF with endothelial function.