Glenn TM, Kasparian NA, Amdani S, et al. The Fontan Outcomes Network: Findings After 2 Years and 1121 Participants. Circulation. 2026;153:1182-1195. doi:10.1161/CIRCULATIONAHA.125.078152. PMID: 41878814.
PubMed: https://pubmed.ncbi.nlm.nih.gov/41878814/
Take-Home Points
- The Fontan Outcomes Network (FON) enrolled 1,121 patients from 38 congenital heart centers, creating one of the largest prospective Fontan registries assembled to date.
- Fontan-related complications were present in 59% of participants, highlighting the persistent morbidity associated with Fontan circulation.
- Arrhythmias affected 41.3% of patients and increased substantially with advancing age.
- Acquired medical comorbidities were identified in 57.5% of patients, supporting the concept of Fontan circulation as a multisystem disorder.
- Mental health diagnoses were extraordinarily common, affecting 62.3% of participants, with anxiety disorders present in nearly half of adults.
- The FON registry provides a foundation for future collaborative research, quality improvement, benchmarking, and pragmatic clinical trials.
Commentary from Dr. Varun Aggarwal (Wilmington, DE, USA), editor-in-chief of Congenital Heart Disease Journal Watch:
Few populations in congenital heart disease illustrate both the triumphs and limitations of modern cardiovascular medicine better than patients living with Fontan circulation. The Fontan operation transformed a once uniformly fatal collection of congenital heart defects into a chronic disease compatible with survival into adulthood. Contemporary survival now exceeds 85%, and more than 70,000 individuals are estimated to be living with Fontan physiology worldwide. Yet survival has also revealed the price of success. Fontan circulation is not a cure. Rather, it creates a unique hemodynamic state characterized by chronically elevated systemic venous pressure, diminished ventricular preload, and nonpulsatile pulmonary blood flow, exposing patients to progressive complications that often emerge years or decades after surgery.
The current report from the Fontan Outcomes Network provides the most comprehensive contemporary snapshot of Fontan survivors in North America. Drawing from 1,121 patients enrolled across 38 centers, the registry includes children, adolescents, and adults spanning a wide spectrum of diagnoses, surgical eras, and clinical experiences. Notably, hypoplastic left heart syndrome accounted for nearly 40% of the cohort and right ventricular dominant morphology for 55%, reflecting the evolution of congenital heart surgery over the past two decades. The predominance of extracardiac Fontan connections similarly distinguishes this study from many historical cohorts.
The most striking observation was not any single complication, but the cumulative burden of disease. Fifty-nine percent of participants had already experienced at least one major Fontan-related adverse event. Seven percent had developed intracardiac or Fontan pathway thrombosis. More than six percent had experienced a non-perioperative stroke. Protein-losing enteropathy remained present in approximately six percent of patients. These numbers are not merely statistics. They represent a reminder that although Fontan survivors are living longer, many continue to experience substantial cardiovascular morbidity throughout childhood and adulthood.
The age-related arrhythmia data deserve particular attention. A history of arrhythmia was present in 41.3% of the overall cohort, and adults demonstrated a striking increase in atrial tachycardia, atrial flutter, atrial fibrillation, sinus node dysfunction, and ventricular arrhythmias. More than one-quarter of adults had experienced multiple arrhythmia-related complications. These findings reinforce observations from prior Fontan registries and long-term studies demonstrating that arrhythmia increasingly becomes one of the dominant clinical problems encountered in adulthood. For ACHD practitioners, the message is straightforward: rhythm surveillance must remain a lifelong priority.
Equally important is the growing recognition that Fontan disease extends far beyond the heart. Acquired medical comorbidities affected 57.5% of participants and became progressively more common with age. Adults demonstrated increasing rates of chronic kidney disease, esophageal varices, gallbladder disease, restrictive lung disease, systemic hypertension, and sleep-disordered breathing. These observations support a conceptual shift that has been developing within the Fontan community for years. The modern Fontan patient does not merely need a cardiologist. Successful care increasingly requires collaboration among hepatologists, pulmonologists, nephrologists, psychologists, nutrition specialists, and adult congenital heart disease teams.
Perhaps the most important contribution of this paper, however, relates to mental health. More than sixty percent of registry participants carried at least one mental health diagnosis. Anxiety disorders affected 34.1% of the cohort and nearly half of all adults. Mood disorders were present in almost one-third of adults. Nearly one in four adults was prescribed an antidepressant. These rates are several-fold higher than those reported in similarly aged populations in the United States. Historically, Fontan outcomes research has focused on ventricular function, exercise capacity, thrombosis, and liver disease. This study reminds us that psychological health may be equally important in determining long-term quality of life. Mental health screening can no longer be viewed as optional within comprehensive Fontan programs. It is part of standard medical care.
A second underappreciated finding involves neurodevelopmental disease. Nearly one-third of participants had a documented neurodevelopmental diagnosis, including attention-deficit/hyperactivity disorder, communication disorders, intellectual disability, autism spectrum disorder, and motor disorders. Surprisingly, fewer than half had undergone formal neurodevelopmental evaluation. This gap highlights an important opportunity for future quality improvement. While cardiology programs routinely monitor ventricular function and Fontan pressures, developmental outcomes are often assessed inconsistently despite their profound influence on educational achievement, employment, and independence.
The paper also provides insight into contemporary management strategies. Antithrombotic therapy was nearly universal, but substantial variation existed in the use of phosphodiesterase-5 inhibitors, beta-blockers, ACE inhibitors, and other cardiovascular medications. More than 20% of participants were receiving pulmonary vasodilator therapy, a rate considerably higher than reported in several international registries. This variability reflects the absence of high-quality evidence guiding many aspects of Fontan management and highlights the need for collaborative effectiveness research.
Ultimately, the most significant contribution of this report may extend beyond the clinical findings themselves. The Fontan Outcomes Network represents a learning health system designed not only to collect data but also to improve care. As FON merges with broader Single Ventricle Outcomes Network initiatives, the congenital heart community gains an unprecedented opportunity to benchmark outcomes, study uncommon complications, identify best practices, and conduct pragmatic multicenter investigations. In many ways, the registry infrastructure may prove as influential as any individual scientific discovery emerging from it.
Clinical Perspective
The era when Fontan care could be viewed primarily through a cardiovascular lens has passed. This landmark report demonstrates that modern Fontan survivors face substantial burdens of arrhythmia, thrombosis, multisystem organ dysfunction, neurodevelopmental challenges, and mental health disease. The future of Fontan medicine will be defined not only by improving survival, but also by preserving quality of life, maintaining functional independence, and preventing the accumulation of lifelong morbidity. The Fontan Outcomes Network provides an essential platform for achieving those goals.
