Heterotaxy syndrome and associated arrhythmias in pediatric patients

Background: Heterotaxy syndrome (HS) is a rare disorder with complex anatomy involving misarrangements of the cardiac conduction system. Arrhythmias may be related to anatomic variations and contribute to morbidity. Objective: The purpose of this study was to investigate the associations between arrhythmias, anatomy, and outcomes in a large HS cohort. Methods: A single-center retrospective review of patients ≤21 years of age diagnosed with HS was performed. Results: A total of 337 patients were included in the study. During median follow-up of 7 years (interquartile range 2–16 years), 129 patients (38%) had ≥1 clinically significant rhythm disturbance: tachyarrhythmias in 75 (22%), bradyarrhythmias in 29 (9%), and both in 25 (7%). Factors associated with tachyarrhythmia by multivariate analysis were at least moderate atrioventricular valve regurgitation (hazard ratio [HR] 1.66; 95% confidence interval [CI] 1.11–2.50), single ventricle anatomy (HR 2.30; 95% CI 1.09–4.85), and pulmonary venous obstruction (HR 2.33; 95% CI 1.45–3.76). Isomerism subtype was not associated with tachyarrhythmias. In adjusted and unadjusted analyses, bradyarrhythmias (symptomatic sinus/atrial bradycardia and high-grade or complete heart block) were associated with left atrial isomerism (LAI) compared to right atrial isomerism (HR 7.12; 95% CI 3.01–16.9). The overall transplant-free survival of the cohort was 66%. Tachyarrhythmias, but not bradyarrhythmias, were associated with mortality or need for transplant (HR 2.24; 95% CI 1.45–3.46). Conclusion: Clinically significant arrhythmias are common in HS. Although bradyarrhythmias are associated with LAI, tachyarrhythmia occurrence may depend more on hemodynamic and anatomic factors than isomerism subtype. Tachyarrhythmias, but not bradyarrhythmias, are associated with death or need for transplant.