The characteristics and efficacy of catheter ablation of focal atrial tachycardia arising from an epicardial site.

Background Although epicardial structures around the atrium such as adipose tissue possess arrhythmogenicity, little is known about atrial tachycardias (ATs) originating from epicardial sites (Epi-ATs). This study aimed to elucidate the prevalence, characteristics, and outcome after radiofrequency catheter ablation (RFCA) of Epi-ATs and to reveal the association between Epi-ATs and the epicardial structures. Methods The electrocardiographic, electrophysiologic, and anatomical properties and results of RFCA were analyzed in 42 patients with a total of 49 ectopic ATs. Results Six Epi-ATs (12%) were observed in six patients (14%). Four of six were respiratory cycle-dependent ATs and one was a swallowing-induced AT. The Epi-AT origins were adjacent to a pulmonary vein (five cases) and vein of Marshall (one case). A Valsalva maneuver or atropine infusion to define the arrhythmia mechanism affected the appearance of the Epi-ATs. The congruity rate between epicardial adipose tissue and the AT origin was significantly higher (100% vs. 44%, p = .045), and the epicardial adipose tissue volume of the atrium was significantly larger (104.1 vs. 64.6 ml, p = .04) in the Epi-AT group. Endocardial RFCA targeting the AT foci resulted in acute success in five of five cases. However, electrical isolation including of the AT foci resulted in acute failures (two of three cases) or a recurrence (one of one case). Conclusions Six Epi-ATs were associated with thoracic veins and epicardial arrhythmogenic structures. The main cause provoking the Epi-ATs was associated with autonomic nerve activity.