Cryoballoon Better than Drug Therapy for Eliminating Paroxysmal Afib

An investigational cryoablation catheter system that isolates the pulmonary veins proved nearly 10 times more effective than conventional anti-arrhythmic drug therapy in eliminating intermittent (paroxysmal) atrial fibrillation (AF) and the new system was equally safe. Investigators reported these findings from the STOP AF (Sustained Treatment of Paroxysmal Atrial Fibrillation) clinical trial at a late-breaking clinical trials session at the 59th Annual Scientific Sessions of the American College of Cardiology.

One year after therapy, 69.9% of patients treated with the catheter system remained free of atrial fibrillation versus 7.3% on conventional anti-arrhythmic drug therapy (P<.001), said Douglas Packer, MD, who is professor of medicine at the Mayo Clinic in Rochester, MN, and principal investigator of STOP AF.

STOP AF enrolled 245 patients with paroxysmal AF from 26 medical centers in the US and Canada. All patients had failed previously on at least one anti-arrhythmic drug. They were randomized in a 2:1 ratio to either cryoablation (n=163 patients) or treatment with an anti-arrhythmic agent not previously taken (n=82). Over the next 90 days, referred to as a “blanking” period, each patient’s physician was allowed to adjust drug therapy or repeat cryoablation as needed. Then patients were followed at 1, 3, 6, and 9 months.

Both groups had similar baseline demographic and disease characteristics. Median age was 56 years, 77% were male, and mean left ventricular ejection fraction was 60%. At baseline, 60-80% of patients experienced palpitations, rapid heartbeat, and fatigue as their major symptoms.

Cryoablation was initially successful in 98% of patients, and at one year, nearly 70% of these patients were free of AF and had not needed to use a non-study drug or an interventional procedure to treat AF, compared with 7.3% of the group treated with anti-arrhythmic drug therapy.

The new system was not without complications, Packer said. Pulmonary stenosis occurred in 10 veins (7 patients), and two patients had significant stenosis. There were 29 events of phrenic nerve injury in 28 patients. “This was largely reversible. Twenty-five of the 29 events resolved at 12 months,” Packer noted.

He emphasized that the cryoablative catheter system is a relatively new technology for the investigators in the study, and as with any new technology, a learning curve exists. “With experience, the procedure time was reduced,” he noted. “The complication rates are similar to radiofrequency ablation. The potential advantages of cryoablation justify the learning curve,” Packer told reporters.

Once experience with the new system is gained, additional trials will be needed to compare procedure times of different approaches.

The study was sponsored by Medtronic. The Arctic Front® Cardiac CryoAblation Catheter System is available in Europe and some other countries, and is investigational in the United States.