Ablating Electrical 'Rotors' Gets Results in Persistent AF

May 10, 2011

May 6, 2011 (San Francisco, California) — The use of an investigational diagnostic mapping system designed to locate electrical sources not traditionally ablated during conventional atrial-fibrillation (AF) ablation procedures identified localized electrical rotors, or focal drivers, of AF in nearly all patients [1]. Furthermore, ablation of these focal electrical sources, in addition to conventional wide-area circumferential ablation (WACA) of the pulmonary veins, resulted in significantly better outcomes than pulmonary vein isolation alone.

During the late-breaking clinical-trials session here at the Heart Rhythm Society 2011 Scientific Sessions, researchers presenting the results of the unique ablation protocol used in the Conventional Ablation for Atrial Fibrillation with or without Focal Impulse and Rotor Modulation (CONFIRM) trial reported that the mapping technology and subsequent ablation led to improved AF-free survival in patients who underwent ablation of these electrical sources in addition to pulmonary vein isolation.

"The results from the study show that with a single procedure we can improve the success rate over conventional ablation, and we should really evaluate the way we think about atrial fibrillation," said lead investigator Dr Sanjiv Narayan (University of California, San Diego).

"Spinning Waves" of Electrical Activity

Speaking with the media during a morning press conference, Narayan said that "spinning waves" of electrical activity, which he called rotors or focal beats, have been identified in animal models, but there had been no direct evidence that they existed in humans. However, the development of the physiological mapping system of AF allowed researchers to test the hypothesis that these electrical rotors existed in humans and, if stable, would make for attractive sites of localized ablation.

In total, 103 patients were enrolled in CONFIRM. Of these patients, 95 had sustained AF and were randomized to WACA, the primary ablation being complete pulmonary vein isolation, or to WACA and ablation of the identified rotors or focal beats, known as focal impulse and rotor modulation (FIRM). Of the patients included in the trial, approximately 67% had persistent AF.

Narayan explained that during an electrophysiology study, AF is recorded by baskets in the left or both atria and that the novel computational system, developed through grants from the National Institutes of Health and the Doris Duke Charitable Foundation and now licensed to Topera Medical (Lexington, MA), is able to show images and the location of the sources of AF activation. To heartwire , Narayan said the electrical focal beats were located all throughout the atria in patients, including some areas where clinicians would normally perform pulmonary vein isolation. In other patients, however, the activity was located in the anterior and posterior walls of the left atrium, areas of the heart that would not normally be ablated during a conventional procedure. In other patients still, the focal beats were located in the right atrium.

Overall, focal electrical beats were identified in 97% of patients, with patients in both the conventional ablation arm and those in the ablation plus FIRM arm having two sources of electrical rotors per patient. However, the WACA-plus-FIRM protocol successfully terminated or slowed AF in 88% of patients, while AF was terminated or slowed in just 14% of patients undergoing conventional ablation. Regarding AF-free survival at two years, 84% of those treated with WACA plus FIRM were free of the arrhythmia, compared with 50% of patients who received WACA alone.

Terminating AF Quickly

During the clinical-trials session, Narayan noted that the protocol for ablating the electrical rotor beats required FIRM ablation at the source for <10 minutes or until AF was terminated. He noted that the FIRM ablation was able to restore sinus rhythm in as quickly as six minutes prior to conventional ablation and in one patient within a minute. While the electrical mapping system requires additional time prior to the ablation procedure--the initial mapping setup took an hour--this has been reduced to around just 10 minutes, said Narayan.

Dr Douglas Packer (Mayo Clinic, Rochester, MN), the chair of the morning press conference, spoke on the significance of the CONFIRM trial, noting that atrial-fibrillation ablation procedures take an extensive amount of time and that anything that can shorten the procedure--such as identifying sites for localized ablation that can rapidly terminate AF and return patients to sinus rhythm--would be appreciated.

"The thing that I'm most interested in, though, is that this is one of those rare occasions where we're actually going back to real physiology, so that it becomes a physiologically based ablation rather than an anatomically based ablation. I think that's a substantial interest," said Packer.

Narayan reports honoraria from Medtronic, St Jude Medical, Biotronik and fellowship support from Medtronic, Boston Scientific, St Jude Medical, and Biosense. He holds intellectual property rights for the diagnostic technology owned by the University of California Regents, which is currently licensed to Topera. He is a cofounder and equity holder in Topera. Topera does not sponsor research in any of the investigator's trials, including the CONFIRM trial.

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