Early Experience with the First Canadian Paediatric Fontan Long-Term Follow-up Clinic.

The Fontan procedure has significantly improved survival in patients with single-ventricle physiology; however, multisystem complications have become a major source of late morbidity and mortality. In 2020, the Hospital for Sick Children (SickKids) established a dedicated paediatric Fontan Long-Term Follow-up Clinic. This study evaluated the prevalence and spectrum of cardiac and extracardiac morbidities in the clinic cohort since inception. This single-centre retrospective study included all patients referred between January 2020 and December 2024. Standardized assessments comprised cardiac evaluations (echocardiography, Holter monitoring, exercise testing, cardiac MRI) and extracardiac investigations of hepatic, renal, hematologic, endocrine, growth, and neurodevelopmental status. Fontan-associated liver disease (FALD) was graded using MR elastography and imaging findings. A total of 161 patients (mean age 13.2 ± 3.7 years; 58.4% male) were assessed at a mean of 9.5 ± 4.3 years post-Fontan completion. Tricuspid atresia was the most common diagnosis (26.1%). Cardiac function was generally preserved, with mean predicted peak VO₂ of 63.6 ± 17.6%. Moderate or severe atrioventricular valve regurgitation occurred in 21.5%, and ventricular dysfunction in 5.6%. Moderate or greater FALD was observed in 8.0%, with mean magnetic resonance elastography 4.58 kPa (Interquartile range, 4.03-5.40). Lymphopenia (64.6%), thrombocytopenia (16.8%), vitamin D deficiency (41.9%), and reduced bone density (28.0%) were frequent. Neurodevelopmental challenges were common (39.8% learning difficulties). Despite preserved cardiac performance, Fontan patients exhibited a high burden of hepatic, hematologic, endocrine, skeletal, and neurocognitive morbidities. Multidisciplinary, longitudinal follow-up is essential to optimize outcomes and quality of life.