Rotor Locations and 1 Year Outcomes of FIRM Ablation IntroductionPulmonary vein isolation (PVI) is currently the gold standard for catheter ablation of atrial fibrillation (AF). The mechanism for AF-maintenance is still controversial. The concept of rapidly activating spiral rotors perpetuating AF has led to the development of several rotor-mapping systems. We present our experience with focal impulse and rotor modulation (FIRM) using a 64-electrode basket catheter and computational system and evaluate its feasibility in conjunction with PVI to treat AF. Methods and ResultsTwenty-five patients underwent FIRM mapping and ablation to treat AF (paroxysmal = 10, 40%). A basket catheter was used for rotor identification within the right atrium (RA) then left atrium (LA). Radiofrequency energy was applied at and around each rotor core for 300 seconds and rotor-mapping and ablation was repeated until all rotors were eliminated before circumferential PVI was performed. Three (1.0, 4.0) rotors were identified per patient, predominantly in the LA (LA = 59). Note that 7/59 left-sided rotors were located 8/59 at the PV antrum. Twelve (48%) patients had either AF termination (termination = 6/12) or conversion to another rhythm, or cycle length (CL) prolongation 10% after rotor ablation. After a single procedure, 13 (52%) patients were free of atrial tachyarrhythmia after a follow-up period of 13 1 months. ConclusionEarly results suggest that FIRM-ablation can terminate AF in a significant number of patients. Rotors were frequently identified in the PVs and PV antrum, supporting PVI as the cornerstone of AF ablation.