Focal impulse and rotor modulation: Acute procedural observations and extended clinical follow-up

Focal impulse and rotor modulation (FIRM) was based on the premise that atrial fibrillation (AF) is sustained by rotors that are sufficiently stable to be eliminated by targeted ablation. Early experience reported high success as compared to conventional strategies.

The purpose of this study was to report on a single-center experience with extended follow-up by using FIRM in a variety of patients with AF.

All FIRM-guided ablation procedures were included. During spontaneous or induced AF, FIRM software constructed phase maps to identify putative AF sources, then targeted for radiofrequency ablation, with adjunctive pulmonary vein isolation (PVI), if needed. All mapped rotors and/or sources were eliminated on the basis of repeated FIRM mapping.

Of 47 patients, sustained AF was not present or induced in 4 patients who did not undergo FIRM ablation. Of the remaining 43 patients, prior AF was paroxysmal in 9 (21%) and 72% had a median of 1 prior PVI. Spontaneous AF (n = 22, 52%) and induced AF (n = 21, 49%) were mapped, and all patients had rotors identified (1.8 ± 0.8 per patient; 70% in the left atrium). AF termination occurred in 2 patients (5%) and none organized to atrial tachycardia. Touch-up redo PVI was also performed in 31 patients (72%). At 16.0 ± 10.7 months (range 1-34 months), only 9 patients (21%) were free of recurrent AF; and only 5 patients (12%) were free of AF and off antiarrhythmic drugs.

Long-term clinical results after FIRM ablation in this diverse challenging cohort showed poor efficacy. Randomized clinical trials are needed to evaluate the efficacy and clinical utility of the FIRM ablation approach for treating AF.