High-Performing Fontan Patients: A Fontan Outcome Registry by Cardiac Magnetic Resonance Imaging Study

Background: Fontan patients exhibit decreased exercise capacity. However, there is a subset of high-performing Fontan (HPF) patients with excellent exercise capacity. Objectives: This study aims to: 1) create a Fontan-specific percent predicted peak VO₂ tool using exercise data; 2) examine clinical factors associated with HPF patients; and 3) examine late outcomes in HPF patients. Methods: Patients in the multi-institutional Fontan Outcomes Registry Using CMR Examination above the age of 8 years who had a maximal exercise test were included. An HPF patient was defined as a patient in the upper Fontan-specific percent predicted peak VO₂ quartile. Multivariable logistic regression was employed to investigate factors associated with the HPF and Cox regression was used to examine the association between HPF patients and late outcomes (composite of death or listing for cardiac transplant). Results: The study included 813 patients (mean age: 20.2 ± 8.7 years). An HPF patient was associated with left ventricular morphology (OR: 1.50, P = 0.04), mixed morphology (OR: 2.23, P < 0.001), and a higher ejection fraction (OR: 1.31 for 10% increase, P = 0.01). Patients with at least moderate atrioventricular valve regurgitation, protein-losing enteropathy, or who were using psychiatric medications, were less likely to be an HPF patient. After a mean follow-up of 3.7 years, 46 (5.7%) patients developed a composite endpoint. HPF had a lower risk of death or listing for cardiac transplant (HR: 0.06 [95% CI: 0.01–0.25]). Conclusions: Patients with HPF have more favorable outcomes when compared to patients with lower exercise capacity. This large registry data highlights the role of exercise testing in providing personalized care and surveillance post-Fontan.