Anticoagulation Management and Valve-related Outcomes after Mechanical Valve Implantation in Patients with Fontan Palliation

Background Valvular dysfunction is a major contributor to morbidity in adults with Fontan palliation. Mechanical valve replacement offers superior durability compared with bioprostheses but requires lifelong anticoagulation, raising concern in the prothrombotic and low-flow Fontan circulation. Data on long-term outcomes after mechanical valve implantation in this population remains limited. Objectives To evaluate long-term bleeding, thromboembolic, valve-related, and cardiovascular outcomes after mechanical valve replacement in adults with Fontan palliation. Methods We retrospectively studied 26 adults with Fontan circulation who underwent mechanical aortic or atrioventricular valve replacement between 2003 and 2024. Outcomes included (1) major bleeding/thromboembolic complications, (2) valve-related complications, and (3) composite cardiovascular events (valve-related complications, death, or transplant). Events were analyzed as time-to-event endpoints. Anticoagulation control was assessed by time in therapeutic range (TTR). Results Median age at valve implantation was 21 (15–28) years. Fifteen prostheses were implanted in the atrioventricular position and 11 in the aortic position. Median follow-up was 14.3 years (364 patient-years). TTR was 71% for atrioventricular and 79% for aortic prostheses. Four patients experienced major bleeding/thromboembolic events. Ten- and 20-year cumulative incidences of major bleeding/thromboembolism were 9% and 22%, respectively. Valve-related complication rates were 13% and 28% at 10 and 20 years. Composite cardiovascular event rates were 31% and 60% at 10 and 20 years, driven primarily by progressive Fontan failure rather than prosthetic dysfunction. Conclusions Mechanical valve replacement in selected Fontan patients provides durable valve performance with acceptable long-term complication rates. Outcomes appear largely determined by the natural history of Fontan physiology rather than prosthesis-related failure.