Mapping and ablating stable sources for atrial fibrillation: summary of the literature on Focal Impulse and Rotor Modulation (FIRM)

Abstract

Atrial fibrillation (AF) is the most common sustained arrhythmia and the most common indication for catheter ablation. However, despite substantial technical advances in mapping and energy delivery, ablation outcomes remain suboptimal. A major limitation to AF ablation is that the areas targeted for ablation are rarely of proven mechanistic importance, in sharp contrast to other arrhythmias in which ablation targets demonstrated mechanisms in each patient. Focal impulse and rotor modulation (FIRM) is a new approach to demonstrate the mechanisms that sustain AF ("substrates") in each patient that can be used to guide ablation then confirm elimination of each mechanism. FIRM mapping reveals that AF is sustained by 2-3 rotors and focal sources, with a greater number in patients with persistent than paroxysmal AF, lying within spatially reproducible 2.2 ± 1.4-cm(2) areas in diverse locations. This temporospatial reproducibility, now confirmed by several groups using various methods, changes the concepts regarding AF-sustaining mechanisms, enabling localized rather than widespread ablation. Mechanistically, the role of rotors and focal sources in sustaining AF has been demonstrated by the acute and chronic success of source (FIRM) ablation alone. Clinically, adding FIRM to conventional ablation substantially improves arrhythmia freedom compared with conventional ablation alone, and ongoing randomized trials are comparing FIRM-ablation with and without conventional ablation to conventional ablation alone. In conclusion, ablation of patient-specific AF-sustaining mechanisms (substrates), as exemplified by FIRM, may be central to substantially improving AF ablation outcomes.

Quantification of the cryoablation zone demarcated by pre- and postprocedural electroanatomic mapping in patients with atrial fibrillation using the 28-mm second-generation cryoballoon

“…More recently, some specific strategies of substrate ablation have proved to be interesting, including ganglionic plexus 21,22 and rotor ablation procedures. 23,24 While we await more trial data, it is interesting that this second-generation cryoballoon creates lesions that are near the ganglionic plexi on the LA posterior wall. 21 Additionally many stable rotors have been found near the "PV ostia-to-LA antrium" border which is contiguous with the area of cryoballoon ablation.…”

Computer-Aided Clinical Decision Support Systems for Atrial Fibrillation

“…The algorithm/ablation procedure used by Narayan et al was called focal impulse and rotor modulation (FIRM). Based on the outcome of the clinical studies on FIRM-guided ablation and several other follow-up studies, the FIRM algorithm was found to be effective, especially when combined with PVI [53]. The FIRM technology was later commercialized as a clinical diagnosis system for AF, now owned by Abbott Electrophysiology.…”

Cryoablation in persistent atrial fibrillation – a critical appraisal

“…This widely circumferential extension of the cooling area may provide collateral benefit by ablating local contributors in AF triggering and maintenance such as ganglionic plexi and rotors, which may have therapeutic implications among patients with persistent AF [17, 44, 45]. …”