March 27, 2026Circulation
The Fontan Outcomes Network: Findings After 2 Years and 1121 Participants
Key result
Fontan-related adverse events affect ~59% of patients, alongside frequent arrhythmias and clinical anxiety.
- n=1,121
Why the study?
Survival after Fontan palliation for single ventricle heart disease has improved substantially, yet the long-term trajectory remains poorly defined.
Key Points
- This research aims to characterize early outcomes and adverse events in patients who underwent Fontan palliation.
- Cross-sectional analysis of 1121 participants who underwent Fontan palliation
- Data collected from 38 congenital heart centers in the US and Canada
- Demographic, clinical, imaging, procedural, and medication data analyzed descriptively
- Common primary diagnoses included hypoplastic left heart syndrome (38.5%) and right ventricular–dominant anatomy (54.9%)
- 59% of participants experienced Fontan-related adverse events, including chylous pleural effusions (9.6%) and Fontan thrombosis (7.1%)
- 34.1% had a diagnosis of anxiety disorder, with a higher prevalence (48.1%) in adults.
Study Design
Type
Cross-Sectional (n=1,121)
Multicenter
Yes
Structured PICO
P
Population
1121 individuals who had undergone Fontan palliation for single ventricle heart disease, enrolled in the Fontan Outcomes Network from August 2022 through August 2024, mean age 16.3±10.2 years, 42% female, across 38 congenital heart centers in the United States and Canada.
O
Outcome
Demographic, clinical, imaging, procedural, and medication data
The Fontan Outcomes Network registry highlights a high burden of Fontan-related adverse events, arrhythmias, and mental health needs among 1121 participants with single ventricle heart disease.
Discussion
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Key expert perspectives
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
ILIan LawCardiology Division Director, University of Iowa
“This is an amazing accomplishment and once again a testament to what teamwork can do.”
“People with Fontan circulation often develop complications with other organs in the body including the liver, kidneys and lungs. The coordination between our two organizations will generate data and insight that can help patients and clinicians better monitor their health and intervene earlier.”
KKKirstie KellerChief Executive Officer, Additional Ventures
“While lifesaving, Fontan circulation creates complex, lifelong health challenges for single ventricle heart disease patients that we still do not fully understand. Through this collaboration, we will work with researchers, clinicians and patients to generate the scientific insights and tools needed to predict, detect and manage complications earlier.”
Implication
Supports multidisciplinary Fontan care for arrhythmia and anxiety burden; leaves open optimal prevention strategies for adverse events.
Abstract
BACKGROUND: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.
Cite This Study
Glenn et al. (2026) conducted a cross-sectional in Single ventricle heart disease post-Fontan palliation (n=1,121). Among 1121 participants in the Fontan Outcomes Network, 59% experienced typical Fontan-related adverse events, 41.3% had a history of arrhythmia, and 34.1% had a clinical diagnosis of anxiety.