Thromboembolic Prevention in Adolescents and Adults with Long-standing Fontan Circulation: Is ASA Equipotential to Anticoagulation?

Objectives: The risk of thromboembolism increases with duration of Fontan circulation. It is still discussed controversially, when to start preventive medication and which drug should be chosen. We aimed to characterize clinical relevant thromboembolism in long-standing Fontan circulation and to analyze whether acetylsalicylic acid (ASA) is equipotential to vitamin K antagonists (VKA).

Methods: A total of 78 adolescents and adults were included (20.7 ± 5.7 years; 51 male). Last medication and duration of therapy were documented, either prior to thromboembolism or up to the end of observation time. Perioperative events were excluded.

Results: A total of 44 patients were on VKA, 15 on ASA, and 19 without treatment. During a mean observation time of 8.1 ± 5.6 years, 15 (19.2%) patients experienced thromboembolism. Nine patients had deep venous thromboses, among these, five with pulmonary embolism. Supraventricular tachycardia (SVT) occurred in four cases, two with cerebral embolism and thrombus within the Fontan tunnel, respectively. Two patients had an isolated thrombus in the Fontan tunnel.

Time of Fontan circulation was significantly longer in patients with thromboembolism (25.6 ± 8.3 vs. 20.0 ± 5.2 years, p < 0.001). NYHA class was worse (p = 0.03). Lacking treatment (odds ratio [OR]: 10.2; 95% CI: 1.5–66.3) and ASA (OR: 2.8; 95% CI: 0.9–8.12) carried significantly higher risk of thromboembolism than VKA (OR: 0.17 95% CI: 0.09–0.33). Kaplan–Meier analysis did not differ in lacking treatment versus ASA (p = 0.2). VKA treatment was associated with four relevant bleeding complications.

Conclusion: In adolescents and adults with long-standing Fontan circulation, anticoagulation is superior to ASA to prevent thromboembolism attributable to the inability of ASA to prevent deep vein thrombosis and intracardiac thrombus formation in SVT.