Treatment of Atrial Fibrillation by the Ablation of Localized Sources

Abstract

Objectives We hypothesized that human atrial fibrillation (AF) may be sustained by localized sources (electrical rotors and focal impulses), whose elimination (Focal Impulse and Rotor Modulation, FIRM) may improve outcome from AF ablation. Background Catheter ablation for AF is a promising therapy, whose success is limited in part by uncertainty in the mechanisms that sustain AF. We developed a computational approach to map whether AF is sustained by several meandering waves (the prevailing hypothesis) or localized sources, then prospectively tested whether targeting patient-specific mechanisms revealed by mapping would improve AF ablation outcome. Methods We recruited 92 individuals during 107 consecutive ablation procedures for paroxysmal or persistent (72%) AF. Cases were prospectively treated, in a 2-arm 1:2 design, by ablation at sources (FIRM-Guided) followed by conventional ablation (n=36), or conventional ablation alone (n=71; FIRM-Blinded). Results Localized rotors or focal impulses were detected in 98 (97%) of 101 cases with sustained AF, each exhibiting 2.1±1.0 sources. The acute endpoint (AF termination or consistent slowing) was achieved in 86% of FIRM-guided versus 20% of FIRM-Blinded cases (p<0.001). FIRM ablation alone at the primary source terminated AF in 2.5 minutes (median; IQR 1.0–3.1). Total ablation time did not differ between groups (57.8±22.8 versus 52.1±17.8 minutes, p=0.16). During 273 days (median; IQR 132–681 days) after a single procedure, FIRM-Guided cases had higher freedom from AF (82.4% versus 44.9%; p<0.001) after a single procedure than FIRM-blinded cases with rigorous, often implanted, ECG monitoring. Adverse events did not differ between groups. CONCLUSIONS Localized electrical rotors and focal impulse sources are prevalent sustaining-mechanisms for human AF. FIRM ablation at patient-specific sources acutely terminated or slowed AF, and improved outcome. These results offer a novel mechanistic framework and treatment paradigm for AF. (ClinicalTrials.gov number, NCT01008722)

Not all rotors, effective ablation targets for nonparoxysmal atrial fibrillation, are included in areas suggested by conventional indirect indicators of atrial fibrillation drivers: ExTRa Mapping project

“…In addition, a notable feature of the present system is that the phase map is based on myocardial action potentials, which are similar to experiments employing optical mapping systems,11 whereas the phase maps produced by the aforementioned systems14, 16 are based only on the timing of the excitation wavefront propagation.…”

“…One of the systems was proposed by Narayan, et al14 (Topera ® Solution, Abbott Lab., CA, USA). The system employs a 64‐pole basket catheter to conduct a panorama mapping of the atria.…”

2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Patient Selection, Procedural Techniques, Patient Management and Follow-up, Definitions, Endpoints, and Research Trial Design

“…The first identification and targeted ablation of rotational activity with fibrillatory activities was reported in 2005, using the noncontact mapping technique by Lin et al 562 The next system that was developed for clinical use employed two 64-pole basket catheters to obtain simultaneous unipolar endocardial electrograms from 128 locations in both atria of patients undergoing AF ablation. 563 A computational mapping system (Rhythm-View, Topera, Inc.) was used to process the electrograms and generate activation movies of the atrial electrical activity. After considerable processing and interpolation, evidence was found for rotational activity in patients with paroxysmal, persistent, and long-standing persistent AF.…”

“…Both were considered drivers only if they sustained for ≥50 rotations or focal discharges. 563 This approach has recently been validated by linking FIRM simultaneously with optically mapped rotational activity in the same human hearts. 76 Although early reports documented findings showing that this approach to mapping and ablating rotational activity improved outcomes of AF ablation, 223,226,563,565,566,567 more recent studies have failed to confirm these early findings.…”

“…563 This approach has recently been validated by linking FIRM simultaneously with optically mapped rotational activity in the same human hearts. 76 Although early reports documented findings showing that this approach to mapping and ablating rotational activity improved outcomes of AF ablation, 223,226,563,565,566,567 more recent studies have failed to confirm these early findings. 568 Issues associated with the FIRM-guided protocol that have contributed to uncertainty regarding its clinical value include difficulties with basket catheter placement and appropriate electrode contact, and the inability to identify atrial electrogram characteristics expected from rotational activity that differ quantitatively from surrounding tissue.…”