Diastolic dysfunction, atrial mechanics and functional capacity in Fontan circulation: clinical implications for patient surveillance and heart transplant consideration

Background: Patients with Fontan circulation show a progressive decline in exercise tolerance over time, and reliable markers for risk stratification remain limited. Left atrial strain assessed by speckle-tracking echocardiography has emerged as a potential indicator of atrial function and cardiovascular prognosis, but its relationship with functional performance in total cavopulmonary connection (TCPC) patients is still debated. Objectives: To investigate the association between atrial strain parameters and functional capacity measured by cardiopulmonary exercise testing (CPET), and to evaluate their prognostic implications in a cohort of TCPC patients. Methods: A combined retrospective–prospective observational study included 112 TCPC patients ≥12 years old able to perform CPET. Echocardiography with atrial strain analysis and standardized CPET were performed within a 12-month interval. Clinical events (death, heart transplantation or enlisting) were collected during follow-up. Multivariable regression and Cox analysis assessed predictors of functional capacity and outcomes. Results: Mean age was 26.5 ± 7.5 years; 66% had a systemic left ventricle; 81% received an extracardiac conduit. Functional capacity was reduced (VO2max 21.2 ± 4.8 ml/kg/min, 57.1 ± 13.2% predicted), with deterioration over 7.7 ± 2.7 years of follow-up. No significant correlation emerged between atrial strain parameters and CPET indices. Atrial reservoir strain (LASr) correlated with age, systemic ventricular dysfunction, and atrial enlargement. In multivariable models, LASr and VO2max independently predicted adverse events (death/HTx/listing) (AUC = 0.84), while ventricular morphology and Fontan type were not associated with outcomes. Conclusions: In TCPC patients, functional capacity remains impaired and declines over time. Although atrial strain is not directly related to CPET performance, LASr provides independent prognostic information and may support risk stratification when combined with exercise testing. These easily obtainable clinical and echocardiographic markers may help guide timely intervention and transplant referral in Fontan survivors