Abstract 9105: Eliminated Male Advantages in Cardiopulmonary Exercise Testing Performance after Fontan Operation Indicates a Central Mechanism of Decreased Exercise Performance in a Single Ventricle Physiology

Abstract

Background: Fontan patients have significantly diminished exercise performance compared with healthy peers. Sex differences in exercise performance after Fontan operation have not been well characterized. Methods: We retrospectively analyzed cardiopulmonary exercise testing (CPET) of Fontan and age-matched control adolescents. Data were analyzed via one-way analysis of variance (ANOVA) and are shown as mean ± standard deviation. Results: We studied 36 Fontan patients (male 18/female 18) and 65 age-matched controls (male 32/female 33). When compared between Fontan and controls, peak values of heart rate (HR), oxygen consumption (VO2), and work rate (WR), ventilator anaerobic threshold (VAT), and oxygen uptake efficiency slope (OUES) were significantly lower in Fontan than in controls in both sexes. In controls, significant sex differences were noted in peak values of VO2, oxygen pulse (OP), WR, VAT, heart rate dependency (αHR/αWR), OUES, and ventilatory efficiency (αVE/αVCO2) whereas no such sex differences were detected in Fontan patients (Table). Significant sex differences noted in correlations between weight and peak VO2 and between αHR/αWR and peak VO2 in controls were not appreciated in Fontan patients (Figure), suggesting that single ventricle physiology abolished some key male advantages in exercise performance under biventricular physiology including body mass (skeletal muscle mass) effects and stroke volume reserve. Conclusion: Disappearance of male advantages in CPET performance in Fontan patients indicates a limitation of systemic ventricular filling due to the absence of sub-pulmonary ventricle as a central determinant of low exercise performance.