Predictive Role of Atrial Strain, Aortic Stiffness, and Muscle-Related Factors for Maximal and Submaximal Exercise Capacity in Fontan Patients

Fontan patients' exercise capacity and associated risks of morbidity and mortality necessitate a comprehensive study. We aim to explore maximal and submaximal exercise capacity, assessing the impact of cardiovascular and peripheral factors, including atrial strain, aortic stiffness, and muscle-related factors. Fontan patients and matched controls were examined. Clinical details were recorded, and atrial strain and aortic stiffness were measured using echocardiography. Hand grip and knee extensor strength were assessed, and muscle oxygenation was recorded. Cardiopulmonary exercise test determined exercise capacity, with peak oxygen uptake/kg (VO₂/kg) and oxygen uptake efficiency slope/kg (OUES/kg) as markers for maximal and submaximal capacity, respectively. Thirty-one Fontan patients (median age = 18, range = 7-31 years) and 30 controls (median age = 18, range = 7-32 years) were studied. No significant differences in body composition and muscle strength were observed between Fontan patients and controls (p > 0.05). Fontan patients exhibited lower peak VO₂/kg and OUES/kg (p < 0.001 for both), along with decreased atrial strain and increased aortic stiffness compared to controls (p < 0.001). Aortic pulse wave velocity (PWV), left atrial strain contractile phase (LASct), and knee extensor strength independently predicted peak VO₂/kg (R² = 0.514) and OUES/kg (R² = 0.486) in Fontan patients; age was a predictor for peak VO₂/kg. Atrial contractile strain, aortic stiffness, and knee extensor muscle strength are predictors of submaximal exercise capacity; furthermore, age, along with these variables, serves as predictors of maximal exercise capacity in Fontan patients. Evaluating hemodynamic, vascular, and muscular parameters, in conjunction with assessing both maximal and submaximal exercise capacities, is crucial for optimizing disease management in Fontan patients. Clinicaltrials.gov registration: NCT05011565.