Late arrhythmias following Fontan completion: insights from a Korean Multicentre Fontan Registry of over 1000 extracardiac conduit surgeries.

AIMS: Awareness of long-term arrhythmia complications after Fontan surgery is increasing, but the impact of surgical type and risk factors on arrhythmia development remain incompletely understood. METHODS AND RESULTS: We retrospectively analysed 1492 Fontan patients from the Korean multicentre registry (1979-2019), categorized into atriopulmonary connection (AP) (n = 106), lateral tunnel (LT) (n = 234), and extracardiac conduit (ECC) (n = 1143) with a median follow-up of 14 years. Arrhythmias occurred in 13.3% of patients at a median age of 17.3 years (tachyarrhythmias 9.9%, bradyarrhythmias 6.8%). At 20 years, freedom from any arrhythmia, tachyarrhythmia, and bradyarrhythmia was 82.5%, 86.9%, and 90.5%, respectively. On multivariable analysis, AP (HR 5.89, 95% CI 3.75-9.25; P < 0.001) and LT (HR 2.85, 95% CI 1.93-4.21; P < 0.001) were associated with a higher risk of arrhythmia compared with ECC. Older age at Fontan surgery also independently increased arrhythmia risk (HR 1.06, 95% CI 1.03-1.10; P < 0.001). Compared with ECC Fontan, LT Fontan and AP Fontan were associated with a progressively higher risk of both tachyarrhythmias (HR 2.99 and 8.20, respectively) and bradyarrhythmias (HR 2.63 and 5.47, respectively; all P < 0.001). The all-cause mortality rate and Fontan failure rate were 9.3% (0.69 per 100 patient-years) and 20.0% (1.61 per 100 patient-years), respectively. Late-onset arrhythmias were associated with an increased risk of mortality and Fontan failure (P = 0.003 and P < 0.001). CONCLUSION: This large, long-term registry shows that ECC Fontan confers a lower arrhythmia risk than LT or AP, and arrhythmias serve as a marker of Fontan failure and mortality in post-Fontan patients.