The Fontan Outcomes Network: Findings After 2 Years and 1121 Participants

Survival after Fontan palliation for single ventricle heart disease has improved substantially, yet the long-term trajectory remains poorly defined. The Fontan Outcomes Network, a learning health network of 38 congenital heart centers in the United States and Canada, was established to address this gap. We report baseline characteristics and early findings from the first 1121 participants enrolled in this prospective clinical registry.

We performed a cross-sectional analysis of individuals who had undergone Fontan palliation enrolled in the Fontan Outcomes Network from August 2022 through August 2024. Demographic, clinical, imaging, procedural, and medication data were analyzed descriptively, overall and by age group (<12, 12 to <18, and ≥18 years).

A total of 1121 participants were enrolled (mean age, 16.3±10.2 years; 471 [42%] female). Hypoplastic left heart syndrome (n=431 [38.5%]) and right ventricular-dominant anatomy (n=615 [54.9%]) were the most common primary cardiac diagnoses, especially in younger age groups. Extracardiac conduit was the most frequent Fontan type (n=749 [66.8%]). Typical Fontan-related adverse events were noted in 59% of cases (n=662), including chylous pleural effusions (n=108 [9.6%]), Fontan thrombosis (n=79 [7.1%]), and nonperioperative stroke (n=73 [6.5%]). A history of arrhythmia was present in 41.3% of patients (n=463) overall, increasing with age. Acquired comorbidities were present in 57.5% of patients (n=645), including asthma (n=132 [12%]) and sleep apnea (n=103 [9%]), with burden increasing by age. Antithrombotic medication use was nearly universal. Use of other medications varied widely by age, and included β-blockers, angiotensin-converting enzyme inhibitors, and pulmonary vasodilators. A clinical diagnosis of an anxiety disorder was present in 34.1% of patients (n=382), including 48.1% of adults (n=194 of 403), and antidepressants were prescribed in 11.8% of patients (n=132), including 23.6% of adults (n=95 of 403), highlighting the mental health needs of this population.

The Fontan Outcomes Network includes one of the largest prospective, multi-institutional data sets of patients with Fontan circulation. These initial findings demonstrate the potential for a collaborative learning health network to advance research and quality improvement for this rare disease population.