Author + information
- Published online February 1, 2017.
- Hugh Calkins, MD∗ ()
- ↵∗Address for correspondence:
Dr. Hugh Calkins, Johns Hopkins Hospital, Sheikh Zayed Tower 7125R, 1800 Orleans Street, Baltimore, Maryland 21287-6568.
During the past 2 decades, catheter ablation of atrial fibrillation (AF) has emerged as an important treatment option for patients with symptomatic AF refractory to antiarrhythmic drug therapy (1). Despite intense worldwide efforts to improve the safety and efficacy of this procedure, it is well recognized that success rates are modest, particularly when viewed from a long-term horizon (1–3). This is particularly true for patients with persistent AF (3). It is because of this limited long-term efficacy of AF ablation that considerable efforts are focused on new targets for AF ablation. These targets can broadly be grouped as ablation of the “fixed” substrate for AF and the “dynamic” substrate for AF. The purpose of this study was to provide new insights concerning the dynamic substrate for AF as assessed with the FIRM (Focal Impulse and Rotor) mapping system (Abbot Medical, Minneapolis, Minnesota), its relationship to the fixed substrate as assessed with echocardiography, and its potential impact on ablation strategies.
In this issue of JACC: Clinical Electrophysiology, Zaman et al. (4) report the results of a clinical trial that examined the location of electrical rotors and focal AF sources identified with the FIRM system. These electrical rotors and focal AF sources were classified as being within 1 cm from the pulmonary veins (PVs) or >1 cm from the PVs. Data from 3 groups of patients were evaluated. The first group were patients who underwent a de novo ablation for paroxysmal AF (PAF) (n = 41). The second group included patients who underwent a re-do ablation for PAF (n = 38), and the third group consisted of patients who underwent an initial ablation for treatment of persistent AF (n = 96). Patients with persistent AF had a larger left atrial (LA) diameter than either of the PAF groups (which had similar LA diameters). Patients underwent mapping for electrical rotors and focal AF sources using a basket catheter placed initially in the right atrium, followed by the left atrium, combined with the FIRM System. Once the electrical rotors and focal AF sources were identified as ablated, PV isolation was performed. More patients with de novo PAF (78%) had sources near the PVs than the patients with re-do PAF (47%) or persistent AF (47%). Among the 175 patients, ablation restored sinus rhythm directly in 28% of patients and resulted in an organized atrial tachycardia in 19% of patients. The investigators concluded that patients with PAF who had a previous AF ablation resembled patients with persistent AF in the frequency with which electrical rotors or focal AF sources lay >1 cm from the PV ostia. The clinical implications of these data are clear.
Designing and analyzing data from a complex multicenter trial is no easy task, and the investigators should be congratulated. This study had several take-home messages. First, the study provided tantalizing evidence of the potential value of mapping the dynamic AF substrate. Second, the results of this study suggested that assessment of LA size was insufficient to distinguish patients with electrical rotors and focal AF sources that lie in close proximity to the PVs from those with ablation sites that are further removed. Finally, this data might help explain why PV isolation alone is insufficient to control AF in one-third of optimal ablation candidates. As the investigators have noted, perhaps mapping and ablation of the dynamic substrate with the FIRM system in patients with PAF will bring the single procedure success rate far closer to the 90% mark, which is what we are seeking. Despite my interest in the results of this study, I must caution readers that “all that glitters is not gold.” Data such as that presented in this current study were at most hypothesis-generating. To prove that a particular mapping or ablation strategy adds value can only be known when subjected to a prospective randomized clinical trial. It was somewhat frightening to see how quickly ablationists embraced another marker of the dynamic substrate (complex fractionated atrial activity) only to learn years later from the Star AF (Substrate and Trigger Ablation for Reduction of Atrial Fibrillation) study that this ablation strategy was no better, and perhaps worse than PV isolation alone. Despite the obstacles that exist, I remain optimistic that ablation strategies that target both the fixed and dynamic AF substrates will ultimately be developed and proven to be of clinical value. As for electrical rotors and focal AF sources identified with the FIRM system, time will tell.
↵∗ Editorials published in the JACC: Clinical Electrophysiology reflect the views of the authors and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology.
Dr. Calkins is a consultant to Medtronic, Abbot Medical, and Boehringer Ingelheim; and has received research support from Boston Scientific.
Francis E. Marchlinski, MD, served as Guest Editor for this paper.
- American College of Cardiology Foundation
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- 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: a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation
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