Pace mapping for the identification of focal atrial tachycardia origin

Background - Focal atrial tachycardia (FAT) is extremely difficult to map and ablate when it is difficult to induce and nonsustained. The objective of this study is to evaluate the efficacy of pace mapping in identifying the FAT origin. Methods and Results - The study included 7 patients with drug-refractory FAT who experienced daily multiple episodes before ablation and presented with difficult-to-induce and nonsustained FAT and a distinct P wave morphology. Pace mapping was systematically performed in the areas of interest using 3-dimensional mapping to match the P wave morphology and paced intracardiac activation sequence recorded from multiple catheters. The anatomic origins of FAT were the right pulmonary vein (PV) in 3 patients, mitral annulus, crista terminalis, tricuspid annulus, and right-sided PV via a posterior conduction of previous PV isolation. In all patients, pace mapping obtained best-matched P wave morphology in ≥11/12 leads of surface ECG at the successful ablation site, and paced intracardiac activation sequence was identical to that of induced FAT. Focal ablation was delivered in 4 patients, including non-PV FAT in 3 and FAT in 1, via posterior gap along the previous right-sided PV isolation, and circumferential right-sided PV isolation was performed in the other 3 patients. No FAT was induced at the end of the procedure. All patients were free of arrhythmias without antiarrhythmic drugs during the 8.4±5.6-month follow-up. Conclusions - The combination of paced P wave morphology and intracardiac activation sequence can be used for the identification of FAT origin in patients with difficult-to-induce and nonsustained FAT.