November 19, 2013

DALLAS, TX – Ablating the source of arrhythmic drivers in the atrial substrate of patients with paroxysmal and persistent AF failed to reduce the recurrence of AF at six months, according to the results of a new study.

In persistent AF, the results showed that the ablation of these triggers in addition to circumferential pulmonary-vein isolation was no better than pulmonary-vein isolation alone for reducing the recurrence of AF at six months or one year. In fact, patients treated with the additional ablation of focal triggers had a significantly increased risk of serious adverse events.

Ablation of rotors driving AF was equally ineffective in paroxysmal AF. In these patients, those who underwent high-frequency ablation of the arrhythmic rotors alone fared no better in terms of AF recurrence at six months than those who underwent circumferential pulmonary-vein isolation. Ablation of the trigger was statistically noninferior to pulmonary-vein isolation for the reduction of AF and atrial tachyarrhythmias at one year.

Dr Felipe Atienza

Presenting the results of the Radiofrequency Catheter Ablation of Drivers vs Circumferential Pulmonary Vein Isolation in Patients with AF (RADAR-AF) study here at the American Heart Association 2013 Scientific Sessions , lead investigator Dr Felipe Atienza (Hospital Gregorio Marañón, Madrid, Spain) believes that the concept of ablating drivers of AF in patients with paroxysmal disease might still play a role.

"There are several trials ongoing and already published in the US, mostly coming from the group of Dr Sanjiv Narayan (University of California, San Diego), which uses a different strategy to identify substrates in AF," Atienza told heartwire . "They use a different computerized system to identify where the rotors are based, and our results are in keeping with them in the sense that in paroxysmal AF patients you might not need to isolate all four pulmonary veins, but [ablate] the site maintaining AF."

Radar Speed Trap: Better Mapping Needed

The RADAR-AF study involved 113 patients with paroxysmal AF, including 58 patients who underwent circumferential pulmonary-vein isolation and 55 randomized to high-frequency ablation of the AF source using mapping software to identify the triggers (EnSite NavX, St Jude Medical). In those with persistent AF, 58 patients were randomized to circumferential pulmonary-vein isolation and 59 to high-frequency source ablation plus pulmonary-vein isolation. The paroxysmal AF analysis was designed as a noninferiority analysis, whereas the persistent AF analysis was designed to test whether high-frequency source ablation was superior to circumferential pulmonary-vein isolation.

In paroxysmal AF, ablation of the AF drivers failed to show statistical noninferiority vs pulmonary-vein isolation for the primary end point of freedom from AF at six months. When investigators included patients who underwent additional ablation procedures within the first year, ablation of the AF drivers fared as well as pulmonary-vein isolation, with 69% of patients in both arms free from AF at 12 months.

In persistent AF, there was no benefit to ablating the AF driver when added to pulmonary isolation. Serious adverse events occurred in 24% of the persistent-AF patients who underwent source ablation plus pulmonary-vein isolation vs 10% of patients who underwent circumferential pulmonary-vein isolation alone.

For Atienza, the way forward will include a technique that avoids ablating "everywhere in the atrium" without clear knowledge of the mechanisms underlying AF. This future will involve pursuing lines of investigation like theirs and Narayan's that focus on the specific sites that maintain the disease.

Dr Mark Link

Commenting on the study results, Dr Mark Link (Tufts University School of Medicine, Boston, MA) said that ablation of AF using circumferential pulmonary-vein isolation has a success rate of approximately 70%, and the hope has been that ablation of drivers within the atrial substrate could improve those rates.

"This trial does not kill the notion that the substrate is important," Link told heartwire , "especially because in paroxysmal AF just ablating the substrate did just as well as our standard ablation. I think it keeps the theory alive, but what it does say is that this current technique for identifying rotors is inadequate and that we need better techniques. There are a number of ongoing clinical trials looking at this, so while I would say that it's not standard of care to do rotor or substrate ablation, there will be more trials coming out in the future."

The RADAR-AF trial was sponsored by an unrestricted grant from St Jude Medical and the National Center for Cardiovascular Research in Spain .

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