Atrial function in Fontan patients assessed by CMR: Relation with exercise capacity and long-term outcomes

Objective: To assess the role of atrial function on exercise capacity and clinical events in Fontan patients. Design: We included 96 Fontan patients from 6 tertiary centers, aged 12.8 (IQR 10.1–15.6) years, who underwent cardiac magnetic resonance imaging and cardiopulmonary exercise testing within 12 months of each other from 2004 to 2017. Intra-atrial lateral tunnel (ILT) and extracardiac conduit (ECC) patients were matched 1:1 with regard to age, gender and dominant ventricle. The pulmonary venous atrium was manually segmented in all phases and slices. Atrial function was assessed by volume-time curves. Furthermore, atrial longitudinal and circumferential feature tracking strain was assessed. We determined the relation between atrial function and exercise capacity, assessed by peak oxygen uptake and VE/VCO₂ slope, and events (mortality, listing for transplant, re-intervention, arrhythmia) during follow-up. Results: Atrial maximal and minimal volumes did not differ between ILT and ECC patients. ECC patients had higher reservoir function (21.1 [16.4–28.0]% vs 18.2 [10.9–22.2]%, p =.03), lower conduit function and lower total circumferential strain (13.8 ± 5.1% vs 18.0 ± 8.7%, p =.01), compared to ILT patients. Only for ECC patients, a better late peak circumferential strain rate predicted better VE/VCO₂ slope. No other parameter of atrial function predicted peak oxygen uptake or VE/VCO₂ slope. During a median follow-up of 6.2 years, 42 patients reached the composite end-point. No atrial function parameters predicted events during follow-up. Conclusions: ECC patients have higher atrial reservoir function and lower conduit function. Atrial function did not predict exercise capacity or events during follow-up.