Fontan Registry: A Single–center Retrospective Study on Long–term Follow–up in Fontan Patients

Background The Fontan procedure is a palliative surgical strategy for patients with single–ventricle congenital heart disease. Although surgical advances have improved survival, Fontan patients remain exposed to multiple late complications, including arrhythmias, thromboembolic events (TE), protein–losing enteropathy (PLE), and liver disease. Purpose To evaluate long–term clinical outcomes in adult Fontan patients and to explore the impact of Fontan surgical techniques and underlying congenital defects on prognosis. Methods We conducted a single–center retrospective cohort study using data from the institutional Fontan Registry between January 2005 and December 2023. Seventy–seven adult patients with a minimum follow–up of two years after Fontan completion were included. Data on surgical history, complications, antithrombotic therapy, hospitalizations, and survival were analysed. Results The cohort included 77 patients (mean age 31.6 ± 9.6 years, 58% male). Tricuspid atresia was the most frequent diagnosis (38%), followed by double–inlet left ventricle (13%). Total cavopulmonary connection with extracardiac conduit was performed in 69%. Arrhythmias were the most common complication (43%), particularly in atriopulmonary connections. TE occurred in 18%, mainly intracardiac thrombosis and pulmonary embolism. TE rates were higher in patients not receiving antithrombotic therapy (43%) compared with those on aspirin or anticoagulation. Hemorrhagic complications occurred in 19%, with major bleeding in 5%. PLE was diagnosed in 12% of patients, requiring repeated hospitalizations. Liver disease, including fibrosis or cirrhosis, was detected in 39%. Among female patients, 15% experienced pregnancy, with one arrhythmic complication requiring cardioversion. The annual hospitalization rate was 0.236 per patient–year. Overall mortality was 9%, mainly related to heart failure and PLE. Conclusions Despite improved survival, adult Fontan patients remain burdened by significant long–term morbidity. Arrhythmias and thromboembolic events have a major impact on prognosis, while liver disease and PLE contribute to hospitalizations and disease complexity. These findings emphasize the importance of lifelong, multidisciplinary follow–up, careful risk stratification, and individualized management strategies to improve outcomes and quality of life in this growing population.