Background: Advancements in cancer treatments for children, adolescents, and young adults (CAYAs) over recent decades have significantly improved their prognosis. However, these advancements have also led to an increased risk of developing various cardiovascular diseases, such as arrhythmias. Atrial fibrillation (AF) the most common arrhythmia in the general population, becomes more prevalent with age (1). The risk of developing AF is elevated in patients with cancer compared to the general population (2). Nevertheless, symptomatic arrhythmias remain uncommon among long-term survivors of childhood cancer (3).

Purpose: The main objective of this study was to explore the rates and risk of arrhythmias in CAYAs with cancer compared to controls.

Method: The Rebuc study is a retrospective matched cohort study that encompasses all young cancer patients (<25 years) in Sweden from 1958 and 2021, with a total of 65,173 individuals matched with 312,935 controls. All individuals with an arrhythmia diagnosis were identified and compared for the following arrhythmias: AF and atrial flutter (ICD-10: I48), supraventricular tachycardia (I47.1), ventricular tachycardia (I47.2), ventricular fibrillation (I49.0), sick sinus syndrome (I49.5), second- and third-degree atrioventricular block (AV-block) (I44.1 and I44.2).

Results: A total of 12,415 individuals with arrhythmias were identified, 2,352 CAYAs (3.6%) and 10,063 controls (3.2%) (Odds Ratio (OR) 1.13 95% CI 1.08-1.18, p<0.0001).

CAYAs had a higher risk of ventricular fibrillation, (OR 1.66 95% CI 1.22-2.27, p= 0.001) and the risk of third-degree AV-block was also 66% higher (OR, 95% CI 1.32-2.07, p<0.0001) compared to controls. CAYAs had no elevated risk for AF but were 1 year younger when diagnosed (60 vs. 61 years, p= 0.03). No significant difference was found in risk for supraventricular and ventricular tachycardias, second-degree AV-block or sick sinus syndrome.

Conclusion: CAYAs have a higher risk for life-threatening arrhythmias such as ventricular fibrillation and third-degree AV-block.

The risk of AF and other supraventricular arrhythmias was similar, but CAYAs experienced AF at a younger age than controls.