Ablation of Localized Sources Improves AF Outcomes: CONFIRM Published

July 18, 2012

July 18, 2012 (San Diego, California) — An ablation procedure that targets reentrant circuits or focal impulses in the atria successfully terminated or slowed atrial fibrillation (AF) and improved clinical outcomes compared with a conventional ablation approach, research shows. After nine months of follow-up, focal impulse and rotor modulation (FIRM) combined with conventional ablation to isolate the left and right pulmonary veins resulted in greater freedom from AF compared with conventional ablation alone, report investigators [1].

"Brief ablation (FIRM) at patient-specific AF-sustaining sources was able to terminate or consistently slow persistent or paroxysmal AF before any conventional ablation in 86% of patients and substantially increase long-term AF elimination using very rigorous monitoring compared to conventional AF ablation alone," according to Dr Sanjiv Narayan (University of California, San Diego) and colleagues.

First presented at the Heart Rhythm Society 2011 Scientific Sessions and reported by heartwire at that time, the study results were published online today in the Journal of American College of Cardiology.

In accompanying editorial [2], Drs Karl-Heinz Kuck and Erik Wissner (Klinik St George, Hamburg, Germany) congratulate the researchers for "bringing to the electrophysiology community a truly novel approach to AF ablation," a procedure that has enormous potential if investigators can reproduce their results. Overall, however, the editorialists say that the novel FIRM-guided procedure might one day allow electrophysiologists to shift from a "blind" substrate-based approach to a "mechanistic ablation strategy targeting localized sources within the atria that perpetuate AF."

Taking on Localized Sources in the Atria

In the Conventional Ablation With or Without FIRM (CONFIRM) trial, 92 patients with symptomatic AF underwent 107 consecutive ablation procedures. Patients were randomized 1:2 to conventional ablation or FIRM-guided ablation followed by conventional ablation. Among the entire cohort, electrical rotors and focal impulses were present in 97% of patients with AF, of which 70% were rotors and 30% were focal impulses.

In terms of the prespecified acute efficacy end point, 31 of 36 patients treated with FIRM-guided ablation achieved AF termination or >10% AF slowing (approximately 15–20 ms prolongation of the AF cycle length). Of these 31 patients, AF was completely terminated in 20 subjects. Of patients who underwent conventional ablation alone, the acute efficacy end point was achieved in 13 of 65 subjects (p<0.001 vs FIRM-guided ablation). After a median of 273 days, 82.4% of patients in the FIRM-guided ablation arm were free from AF compared with 44.9% of patients treated with conventional ablation (p<0.001). The between-group difference was similar when patients who remained on antiarrhythmic medications were excluded from the analysis.

"FIRM-guided ablation was more effective than conventional ablation for patients undergoing their first procedure as well as for patients with prior conventional ablation, who were included to compare the mechanisms of AF across a wide range of presentations," write Narayan and colleagues. "Moreover, FIRM-guided ablation showed substantial efficacy benefit despite the use of highly sensitive implanted ECG monitors in 88% of cases."

One roadblock for now, according to the editorialists, is that the computational software used to create maps of the reentrant circuits and localized impulses is proprietary software (Topera Medical, Lexington, MA), and details about how the maps are created are yet to be published or reproduced by others. In addition, they note that results might not have been as successful if only patients with persistent AF were included in the trial, given that the role of localized sources in patients with longstanding persistent AF is unknown.