SAN FRANCISCO – Catheter ablation of a novel atrial fibrillation source that is identifiable via a new type of diagnostic mapping system resulted in greatly improved long-term atrial fibrillation–free survival rates, compared with conventional ablation, in the CONFIRM study.
This unique computational mapping system visualizes a stable source of AF known as a localized electrical rotor, which can be located anywhere in the atrium.
Dr. Douglas L. Packer
Animal studies have shown that AF is driven by these rotors. Now the novel diagnostic mapping system makes it possible for the first time to identify these same rotors in human AF so that they can be targeted for localized ablation, Dr. Sanjiv Narayan explained at the annual meeting of the Heart Rhythm Society.
As a consequence, at 2 years of follow-up in the 103-patient CONFIRM (Conventional Ablation With or Without Focal Impulse and Rotor Modulation) study, the rate of freedom from AF – as documented in most cases by continuous ECG monitoring via an implanted device – was 84% with rotor ablation plus a standard WACA (wide area circumferential ablation) for pulmonary vein isolation, which was significantly higher than the 51% rate in control patients who received WACA alone.
"The promising results of the CONFIRM trial provide a new paradigm" for the treatment of AF, said Dr. Narayan of the University of California, San Diego.
CONFIRM participants had relatively advanced and thus difficult-to-treat sustained AF. Two-thirds had persistent AF; the rest had paroxysmal AF. Their mean left atrial diameter was significantly enlarged (47 mm), and they averaged 1.9 failed antiarrhythmic drugs. Computational mapping identified localized rotors in all but two patients. The average number of rotors found was two.
Dr. Sanjiv Narayan
Acute termination or substantial slowing of AF was achieved during the ablation procedure in 88% of the 32 patients who underwent the FIRM (focal impulse and rotor modulation) form of ablation, compared with 14% of 71 control subjects who had conventional pulmonary vein isolation via WACA. Time to AF termination (typically to sinus rhythm) averaged 7 minutes in the FIRM group, compared with 4 minutes in WACA-only controls.
The diagnostic mapping takes a bit more than 10 minutes on average, and FIRM ablation takes another 10 minutes, adding a total of about 20 minutes to the typical 60- to 90-minute ablation time for a conventional WACA ablation. However, the incorporation of linear lesions and other sophisticated ablation techniques in complex cases can boost the ablation time to 5-7 hours, and the high 2-year success rate that was seen in CONFIRM suggests that ablating rotors may render these far longer, more elaborate ablation procedures superfluous, according to Dr. Narayan.
He also plans to study whether stand-alone FIRM ablation can replace FIRM plus WACA.
Heart Rhythm Society President Douglas L. Packer commented that because AF ablation procedures take a substantial amount of time, a technical advance that shortens that time "would be of enormous significance" to operators, patients, and payers.
"The thing that I’m most interested in, though, is that this would represent one of those rare occasions where we’re actually going back to a physiologically based treatment rather than simply an anatomically based ablation," observed Dr. Packer, professor of medicine and director of the translational electrophysiology research laboratory at the Mayo Clinic, Rochester, Minn.
CONFIRM was funded by grants from the National Institutes of Health and the Doris Duke Charitable Foundation. Dr. Narayan disclosed that he has an equity interest in Topera Inc., which has licensed the computational diagnostic mapping technology used to target electronic rotors for ablation.