Arrhythmias in congenital heart disease: A nationwide cohort study.

Background: As more patients with congenital heart disease (CHD) survive into adulthood, the population of adults with CHD is expanding. This trend is accompanied by an increasing incidence of complications, including arrhythmias. However, the long-term risk of arrhythmias remains sparsely investigated.
Methods: In this observational cohort study, all Danish patients with CHD born from 1977 to 2024 were identified using registries and followed from date of birth until the occurrence of arrhythmia, emigration, death, or end of follow-up (March 2024). The risk of arrhythmias was assessed among patients with CHD and compared to age- and sex-matched controls from the background population.
Results: A total of 45,820 patients with CHD (50.9% men) were identified and matched with 183,280 controls from the background population. During a median follow-up of 21.5 years, 2.6% of patients with CHD and 0.2% of controls developed arrhythmias-corresponding to incidence rates (IR) of 1.2 (95% CI 1.2-1.3) and 0.1 (95% CI 0.1-0.1) per 1,000 PY, respectively, and a hazard ratio (HR) of 16.4 (95% CI 14.4-18.7). The most common arrhythmias in patients with CHD were advanced atrioventricular block (IR 0.4 [95% CI 0.4-0.4] per 1,000 PY) and atrial flutter/fibrillation (IR 0.5 [95% CI 0.5-0.6] per 1,000 PY). Patients with malformations of the heart chambers, transposition of the great arteries, tetralogy of Fallot, and atrioventricular septal defect were at the highest risk of arrhythmias. Moreover, the risk of arrhythmias among those with ASD was not negligible. In patients with CHD, arrhythmia was associated with a significantly higher risk of death (HR of 6.9 [95% CI 5.9-8.1]).
Conclusions: Patients with CHD are at significantly higher risk of arrhythmias than the background population, and those with complex CHD are at particularly high risk. In patients with CHD, arrhythmia is associated with an increased risk of death. Additional studies are warranted to investigate how we can improve the diagnosis and management of arrhythmias in CHD.
Competing Interests: Disclosures None declared.
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