Abstract 11664: Contractile Reserve is Impaired in Patients After Fontan Operation and Predicts Exercise Performance on Exercise Stress Echocardiography

Abstract

Introduction: Exercise capacity is diminished in Fontan patients. There is limited understanding of their contractile reserve, or ventricular response to exercise. We sought to evaluate contractile reserve in Fontan patients and its association with exercise performance using exercise stress echocardiography. Methods: Single center prospective study of Fontan patients (n=56) and healthy controls (n=11) presenting for cardiopulmonary exercise test and rest/peak exercise research echocardiograms. Contractile reserve was defined as the change in the systemic ventricle’s global longitudinal strain (GLS), free wall strain (FWS) and global circumferential strain (GCS) (and strain rates) from rest to peak exercise. Fontan fenestration mean gradient was obtained by Doppler interrogation. Exercise outcomes included percent predicted maximum oxygen consumption (%mVO2), maximum work and oxygen pulse. Results: Fontan patients were 14.5 ± 4.4 years old at testing and (58%) males. There was a fenestration in 33 patients. Exercise parameters in Fontan patients were abnormal with reduced %mVO2 of 75.5 ± 21.5%. Most strain parameters were lower in Fontan patients than controls at rest and peak exercise. There was a significant increase in fenestration gradient from rest to peak exercise. GLS, GCS strain and GLS, GCS and FWS rates increased significantly from rest to peak exercise in both groups, but the magnitude of increase was significantly less in Fontan patients compared to controls, indicating reduced contractile reserve. An increase in FWS rate at peak exercise was independently associated with better %mVO2 and oxygen pulse in Fontan patients. Conclusions: Fontan patients have abnormal response to exercise with reduced contractile reserve compared to controls. Greater contractile reserve is associated with better exercise performance in these patients. Therapies aimed at increasing contractile reserve after the Fontan may improve exercise performance.