P2.B032: Exercise capacity, muscle mass, and endothelial function in pediatric Fontan patients: Does the type of the single ventricle matter?

Background: Patients who have undergone Fontan circulation often fall under the same classification as “single ventricle patients.” While the differences between patients with a single right ventricle (RV) versus a single left ventricle (LV) have been explored, enhanced knowledge of the single ventricle type and its impact on disease progression is important. Here, we present baseline data of pediatric Fontan patients prior to entering a controlled randomized exercise intervention (RE-ENERGIZE FONTAN) and how single ventricle types may impact their overall health.

Methods: This randomized controlled trial utilizes live video conferencing to deliver a supervised exercise intervention. Fontan patients 8-19 years of age who have been cleared to exercise by their cardiologist are included. Patients with NYHA Class IV, recent acute illness, active protein-losing enteropathy, pacemaker, and/or cognitive delay are excluded. At baseline, patients undergo a series of tests. These include a cardiopulmonary exercise test (peak VO2), an assessment of endothelial function (reactive hyperemia index, RHI), measurement of plasma nitrogen oxide (NOx), DXA scan (muscle mass), echocardiographic measures of ventricular function (myocardial strain and 3-dimensional ejection fraction), and isokinetic dynamometry (handgrip and leg strength).

Results: 85 Fontan patients (median age 13.1 years [IQR, 10.5, 15.6]) completed the baseline visit. The median time from Fontan operation was 9.2 years [IQR, 7.0, 12.0]. The average peak VO2 was 1340±529 ml/min, and the indexed peak VO2 was 27.9±6.74 mL/kg/min. RHI and lnRHI were 1.42±0.51 and 0.31±0.32, respectively. When Single RV (n=40) and Single LV (n=45) patients were compared, there was a significant difference between the two groups in longitudinal strain (-13.7±3.7 vs. -16.3±3.8%, p=0.006), 3D-EF (46.0±5.9 vs. 53.4±6.4%, p= < 0.001), and percent predicted O2 pulse (76.0±18.3 vs. 87.3±21.2%, p=0.01). The VE/VCO2 slope approached significance (41.2±7.39 vs. 38.0±7.93, p=0.058). There was not a significant difference between the two groups for peak VO2, endothelial function, muscle mass, and muscle strength indices.

Conclusion: In our cohort, patients with single RV have diminished ventricular systolic function, decreased ability to augment their stroke volume with exercise, and reduced efficiency of ventilation compared to patients with single LV. These findings suggest that single RV patients might be more vulnerable and at risk for faster disease progression compared to single LV patients. Our RE-ENERGIZE FONTAN exercise intervention will provide further information on the impact of aerobic and strength training on cardiac, vascular, and muscle indices in both single RV and single LV patients.