Fontan Registry Reveals High Comorbidity and Anxiety Rates in Adults

Managing the Evolving Multi-Systemic Burden of Fontan Circulation

Fontan palliation has transformed single ventricle heart disease from a once-lethal condition into a chronic, multi-systemic state requiring lifelong specialized care [1, 2]. As this population ages, clinicians face a complex landscape of late-stage complications, including heart failure, protein-losing enteropathy, and Fontan circulatory failure, which is a chronic state of venous congestion and low cardiac output [3, 4]. Current management strategies must balance the risks of atrial arrhythmias, which affect up to 60% of patients, with the necessity of universal thromboprophylaxis to prevent stroke and venous thromboembolism [1, 5]. Despite improved surgical techniques, the cumulative burden of acquired comorbidities and psychosocial challenges continues to impact long-term survival and quality of life [6, 7]. A recent multi-institutional analysis now provides a detailed cross-sectional view of these clinical challenges across the lifespan.

Anatomy and Demographics of the Fontan Outcomes Network

The Fontan Outcomes Network functions as a learning health network, which is a collaborative system where clinical data is used to continuously improve patient care, comprising 38 congenital heart centers across the United States and Canada. This prospective clinical registry enrolled 1121 participants between August 2022 and August 2024 to better define the long-term trajectory of patients who have undergone Fontan palliation. The study population had a mean age of 16.3 ± 10.2 years, with 471 participants (42%) being female. To capture the evolving clinical needs across the lifespan, the researchers analyzed data across three distinct age groups: children under 12 years, adolescents aged 12 to 17 years, and adults aged 18 years and older. This stratification is essential for clinicians to understand how the physiological demands of the Fontan circuit change as patients transition from childhood through puberty and into adulthood.

Prevalence of Arrhythmia and Thromboembolic Complications

The registry highlights the anatomical complexity of the current Fontan population, where hypoplastic left heart syndrome (a congenital defect where the left side of the heart is severely underdeveloped) was the primary cardiac diagnosis for 431 participants (38.5%). Furthermore, right ventricular-dominant anatomy was present in 615 participants (54.9%), a configuration that occurred most frequently in the younger age groups. Regarding surgical technique, the extracardiac conduit (a procedure where a synthetic tube is used to direct systemic venous return to the pulmonary arteries outside of the heart) was the most frequent Fontan type, utilized in 749 participants (66.8%). These baseline characteristics establish a comprehensive framework for understanding the physiological challenges faced by this multi-institutional cohort, particularly as the right ventricle is forced to serve as the systemic pump, a role for which it is not evolutionarily designed.

Acquired Comorbidities and Pharmacological Management

The registry data underscores the substantial clinical burden associated with the Fontan circulation, as typical Fontan-related adverse events occurred in 59% of cases (n=662). Among these complications, chylous pleural effusions (the leakage of lymphatic fluid into the chest cavity due to elevated central venous pressure) were reported in 108 participants (9.6%). Thromboembolic risks remain a significant concern for clinicians managing these patients; specifically, Fontan thrombosis (the formation of blood clots within the Fontan circuit) occurred in 79 participants (7.1%). Furthermore, the study documented that nonperioperative stroke affected 73 participants (6.5%), highlighting the persistent neurological risks that exist independently of the immediate surgical period. Electrophysiological instability represents another major challenge, as the researchers found that a history of arrhythmia was present in 41.3% of patients (n=463) overall. This burden was not uniform across the cohort, as the prevalence of arrhythmia increased with age, suggesting that the cumulative physiological stress on the single ventricle and atria predisposes older patients to rhythm disturbances. For the practicing clinician, these data emphasize the necessity of vigilant screening for both mechanical and electrical complications as patients transition to adult specialized care.

The Escalating Mental Health Crisis in Adult Survivors

The clinical management of the Fontan patient extends well beyond the primary cardiac anatomy, as the registry data reveals a high prevalence of non-cardiac conditions that complicate long-term care. The researchers found that acquired comorbidities were present in 57.5% of patients (n=645), indicating that more than half of this population requires multi-disciplinary oversight. Respiratory and sleep-related issues were particularly prominent; specifically, asthma affected 132 participants (12%), while sleep apnea was present in 103 participants (9%). Notably, the burden of sleep apnea increased by age, suggesting that clinicians should maintain a high index of suspicion for sleep-disordered breathing, which can further exacerbate pulmonary hypertension and heart failure. Pharmacological management in this cohort reflects the complex physiological requirements of maintaining a single-ventricle circulation. The study found that antithrombotic medication use was nearly universal among the cohort, a finding that aligns with the high risk of thromboembolic events inherent to the Fontan physiology. Beyond anticoagulation and antiplatelet therapy, the use of other cardiovascular medications varied widely by age. These treatments included beta-blockers, angiotensin-converting enzyme inhibitors, and pulmonary vasodilators, which are medications used to reduce the workload on the heart and lower the resistance in the lung vasculature. The age-dependent variation in these prescriptions highlights the evolving hemodynamic needs of patients as they age and the potential progression of ventricular dysfunction.

References

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3. Schumacher KR, Rosenthal DN, Batazzi A, et al. The Impact of Fontan Circulatory Failure on Heart Transplant Survival: A 20-Center Retrospective Cohort Study.. Circulation. 2025. doi:10.1161/CIRCULATIONAHA.124.072961

4. Alsaied T, Bokma JP, Engel ME, et al. Factors associated with long-term mortality after Fontan procedures: a systematic review. Heart. 2016. doi:10.1136/heartjnl-2016-310108

5. Ho KM, Bham E, Pavey W. Incidence of Venous Thromboembolism and Benefits and Risks of Thromboprophylaxis After Cardiac Surgery: A Systematic Review and Meta‐Analysis. Journal of the American Heart Association. 2015. doi:10.1161/jaha.115.002652

6. Ponzoni M, Azzolina D, Vedovelli L, et al. Ventricular morphology of single-ventricle hearts has a significant impact on outcomes after Fontan palliation: a meta-analysis. European Journal of Cardio-Thoracic Surgery. 2022. doi:10.1093/ejcts/ezac535

7. Huisenga D, Gemert SLB, Bergen AV, Sweeney JK, Hadders‐Algra M. Developmental outcomes after early surgery for complex congenital heart disease: a systematic review and meta‐analysis. Developmental Medicine & Child Neurology. 2020. doi:10.1111/dmcn.14512