A randomized trial found no benefits â€” and several large drawbacks â€” in the use of ablations guided by focal impulse and rotor modulation in patients with atrial fibrillation.
A randomized trial found no benefits — and several large drawbacks — in the use of ablations guided by focal impulse and rotor modulation (FIRM) in patients with atrial fibrillation (AF).
Investigators randomized 113 patients with either persistent AF or long-standing persistent AF to FIRM ablation only, FIRM plus pulmonary vein isolation or pulmonary vein isolation plus posterior wall plus non-pulmonary vein trigger ablation.
FIRM ablations, which have now been performed for 5 years, use a catheter and a patented algorithm to find and remove electrical rotors in the heart that create AF. Facilities participating in the trials found rotors in all FIRM ablation patients. (They found a mean of 4 ± a standard deviation of 1.2 rotors per patient in the FIRM-only patients and a mean of 4.2 ± 1.7 rotors per patient in the FIRM plus pulmonary vein isolation group.)
In the FIRM-only group, acute success — defined as freedom from AF or atrial tachycardia — was achieved in 12 of 29 patients (41%). In the FIRM plus pulmonary vein isolation group, acute success was achieved after FIRM ablation (and before pulmonary vein isolation) in 11 of 42 patients (26%).
After a follow up period of 12 months ± 7 months, 4 FIRM-only patients (14%), 22 FIRM plus pulmonary vein isolation patients (52.4%) and 32 pulmonary vein isolation plus pulmonary wall plus non-pulmonary vein trigger ablation patients (76%) were free from AF and atrial tachycardia without using anti-arrhythmic drugs (log-rank p<0.0001). Patients in the last group experienced higher success compared to patients in the FIRM-only group (p < 0.001) and patients in the FIRM plus pulmonary vein isolation group (p = 0.02).
The use of FIRM ablation was associated not only with inferior outcomes but also significantly (p < 0.001) longer operations. Procedure time was 222 minutes ± 49 minutes in the FIRM-only group, 233 minutes ± 48 minutes in the FIRM plus pulmonary vein isolation group and 131 minutes ± 51 minutes in the no-FIRM group.
“This is the first randomized study that compared three ablation strategies in non-paroxysmal AF patients and reported a very poor outcome with rotor-only ablation,” the study authors wrote in the Journal of the American College of Cardiology. “Moreover, pulmonary vein isolation plus rotor ablation had significantly longer procedure time and lower efficacy than pulmonary vein isolation + posterior wall + non-pulmonary vein trigger-ablation.”
Several earlier non-randomized studies had found evidence that FIRM ablations might out-perform other procedure types, but the new randomized trial was not the first to question the benefits of FIRM.
Investigators led by Roland Tilz, MD, presented disappointing findings last year at the Scientific Sessions of the European Heart Rhythm Association. Tilz’s group followed 25 patients who underwent FIRM ablation using a 64-electrode basket catheter and found that FIRM ablation terminated or slowed AF in only half of all patients and that the condition recurred in 25% of patients after 1 year.
The results of the new trial, which was stopped for futility, may be bad enough to significantly reduce usage of FIRM ablations, even if tweaks are made to the technology.
"Unless there is a new version of rotor mapping that I feel is significantly different, probably in my lab and probably in the lab of other . . . investigators, this will be the end of rotor ablation with this system," said Andrea Natale, MD, who spoke about the findings during the Heart Rhythm Society’s 2016 Scientific Sessions. "I think the community is kind of split between the believer and the nonbeliever; I am not [a believer]."