Mechanisms of Intra-Atrial Re-Entrant Tachycardias in Congenital Heart Disease: Types and Predictors.

Intra-atrial re-entrant tachycardia (IART) is a severe complication in patients with congenital heart disease (CHD). Cavotricuspid isthmus (CTI)-related IART is the most frequent mechanism. However, due to fibrosis and surgical scars, non-CTI-related IART is frequent. The main objective of this study was to describe the types of IART, circuit locations, and to analyze predictors of CTI versus non-CTI-related IART. This is an observational study that includes all consecutive patients with CHD who underwent a first IART ablation in a single referral tertiary hospital from January 2009 to December 2015 (94 patients; 39.4% women; age: 36.55 ± 14.9 years, 40.4% with highly complex cardiac disease). During the study, 114 IARTs were ablated (1.21 ± 0.41 IARTs per patient). CTI-related IART was the only arrhythmia in 51% (n = 48) of patients; non-CTI-related IART was the only mechanism in 27.7% (n = 26), and 21.3% of patients (n = 20) presented the two types of IART. Severe dilation of the systemic ventricle, absence of severe dilation of the venous atrium, highly complex cardiac defects, and nontypical electrocardiography (ECG) were related to non-CTI-related IART in univariate analysis. In multivariate analysis, nontypical ECG (odds ratio 3.64; 1.01 to 4.9; p = 0.049) and grade III CHD complexity (odds ratio 9.43; 1.44 to 11.7; p = 0.001) were predictors of non-CTI-related IART. In conclusion, in our population with a high proportion of complex CHD, CTI-related IART was the most frequent mechanism, although non-CTI-related IART was present in 49% (alone or with concomitant CTI-related IART). High-grade CHD complexity and nontypical ECG were strongly related to non-CTI IART.