# Comparison of Arrhythmia Prevalence and Incidence in Adult Patients with Lateral Tunnel and Extra-Cardiac Fontan Circulation

## TL;DR

This study compares arrhythmia rates in adult patients with two types of Fontan circulation and finds higher arrhythmia prevalence in those with lateral tunnel Fontan.

## Contribution

The study provides new evidence on arrhythmia burden differences between lateral tunnel and extra-cardiac Fontan patients in adulthood.

## Key findings

- Patients with lateral tunnel Fontan had a higher prevalence of arrhythmias (57.9%) compared to extra-cardiac Fontan patients (35.6%).
- Lateral tunnel Fontan patients were at greater risk of developing new arrhythmias and required more procedures like cardioversion and ablation.
- The findings suggest the need for tailored screening and risk assessment for lateral tunnel Fontan patients.

## Abstract

Although patients with total cavopulmonary connection (TCPC) Fontan are known to have a lower incidence of arrhythmias compared with atriopulmonary Fontan, there is debate about long-term prevalence of arrhythmia in the TCPC population or about the differences in arrhythmia burden between patients with lateral tunnel (LT) and extra-cardiac (EC) Fontan circulations. A retrospective cohort of 341 patients with LT and EC Fontan operations was identified in a single adult congenital heart disease (ACHD) center. Arrhythmias and related procedures were recorded. Logistic regression was used to determine factors affecting arrhythmia prevalence. Arrhythmia incidence was compared using interval-censored Cox regression. Of 341 patients, 254 (74.5%) had LT Fontan and 87 (25.5%) had EC Fontan. Patients with LT Fontan were older at their last ACHD follow-up (29 versus 25 years). Arrhythmia occurred in 52.2% of patients, 57.9% of the LT and 35.6% of the EC Fontan group. Compared to EC Fontan patients, patients with LT were both more likely to have an arrhythmia (OR 1.84, 95% CI 1.04–3.24) and at a higher risk of developing a new arrhythmia (HR 1.67, 95% CI 1.10–2.54). Patients with LT had more cardioversions, ablations, and revisions compared with EC Fontan patients. However, a similar proportion in each group were treated with antiarrhythmics and had a pacemaker. We summarize arrhythmia burden in a large single-center adult cohort of patients with TCPC Fontan, demonstrating increased arrhythmia in patients with LT. This work can inform screening protocols and risk assessment for this growing population.

The online version contains supplementary material available at 10.1007/s00246-025-03950-1.