Twin atrioventricular nodes, arrhythmias, and survival in pediatric and adult patients with heterotaxy syndrome.

BACKGROUND: Heterotaxy syndrome is likely to involve arrhythmias from associated conduction system abnormalities, which are distinct in different subtypes of isomerism and may change further after interventions and remodeling. OBJECTIVE: The purpose of this study was to understand the risk of arrhythmias and its relation to isomerism subtypes. METHODS: Patients diagnosed between 1980 and 2019 as having heterotaxy syndrome were enrolled and grouped as right atrial isomerism (RAI), left atrial isomerism (LAI), or indeterminate isomerism. RESULTS: Of the 366 patients enrolled, 326 (89.1%) had RAI, 35 (9.6%) LAI, and 5 (1.4%) indeterminate isomerism; 71 (19.4%) patients were adults. Arrhythmias occurred in 37.2% of patients (109 supraventricular tachycardia [SVT], 8 atrial fibrillation/flutter, 12 ventricular tachycardia, and 14 paced bradycardia). Freedom from arrhythmias by the age of 1, 5, 10, 20, and 40 years was 0.849, 0.680, 0.550, 0.413, and 0.053, respectively. Twin atrioventricular nodes were identified in 51.5% of patients with RAI, 8.7% of patients with LAI, and 40.0% of patients with indeterminate isomerism and were the key predictors of SVT. Indeterminate isomerism was also a risk factor for SVT. Other forms of tachycardia appeared relatively late. Sinus bradycardia with junctional rhythm was common in LAI (48.7%) and less in indeterminate isomerism (20.0%), with none occurring in RAI. Only in patients with RAI who showed the poorest survival, ventricular tachycardia worsened the long-term survival. CONCLUSION: RAI was the predominant subtype of heterotaxy in this cohort. Collectively, the median RAI/LAI ratio was 0.731 and 5.450 in Western and East Asian studies, respectively. Arrhythmias, tachycardia, or paced bradycardia were common, but the spectrum was distinct among subtypes.