Study Shows Cryoablation Beats Antiarrhythmic Drugs for Treating Paroxysmal Atrial Fibrillation

March 15, 2010 7:14 AM CT

By Peggy Noonan and Mellanie True Hills

Important new research on treatments for people with paroxysmal atrial fibrillation (AF) was released this morning. Researchers found a form of catheter ablation called cryoablation worked better than drugs to control arrhythmias in people with paroxysmal atrial fibrillation. 

One year after treatment, 69.9% of people in the study who were treated with cryoablation had no episodes of AF, compared to 7.3% of those who were treated with anti-arrhythmic medications. The data came from the STOP AF (Sustained Treatment of Paroxysmal Atrial Fibrillation) clinical trial that was presented at the 59th Annual Scientific Sessions of the American College of Cardiology (ACC) in Atlanta, Georgia, and applies only to people with paroxysmal AF.

Cryoablation is a type of catheter ablation that uses extreme cold or freezing to block conduction of signals that trigger AF, such as where the pulmonary vein enters the left atrium, or upper chamber of the heart. This minimally-invasive procedure is monitored with fluoroscopy and does not require 3-D electroanatomical mapping systems.

What’s different about this trial, besides using cryo as the energy source, is that it involved both a single-point cryo-catheter and a cryoballoon, which inflates and fills with coolant for a 360 degree conduction block at the base of the pulmonary veins.

For this study, a total of 245 people were enrolled in the multi-center trial that was conducted at 26 US and Canadian medical centers. The paroxysmal AF participants were randomized to receive treatment either by cryoablation or anti-arrhythmic drug therapy. For every three people in the study, two (a total of 163 people) received cryoablation treatment compared to one (82 total) treated with anti-arrhythmic medications. Another 65 “crossed over” for cryoablation after they failed drug therapy.

How well did it work? 

Two criteria were used to gauge effectiveness for those who had cryoablation. 

  • Short-term (acute) treatment success, which required electrical isolation of three or more pulmonary veins and was accomplished in 98.2 percent of those who had cryoablation, and
  • Longer-term success, which was 69.9 percent and was defined as absence of detectable AF after the 90-day blanking period, the healing period during which AF events are not counted, or any AF intervention or AF drug not in the study protocol during the 12-month follow-up period.

Is there a downside? 

There were no treatment-related deaths or atrioesophageal fistulas (bleeding between the atrium and the esophagus), but there were complications. Phrenic nerve palsy, a complication that occurs in some catheter ablation procedures, was noted after 29 of the 259 ablation procedures that were done in 228 patients, or 11.2% of the ablation procedures. But after 12 months, 224 of those patients (98.2%) were free of any phrenic nerve injury effects.

Another complication that can occur with ablation is pulmonary vein stenosis, a narrowing or blockage in the veins that carry oxygen-rich blood from the lungs to the left atrium of the heart. In this study, 7 patients (3.1%) developed pulmonary vein stenosis, but only two needed treatment. 

The bottom line 

“These data are a promising indication of the safety profile of cryoablation and its effectiveness in isolating the pulmonary veins to stop AF,” according to STOP AF investigator Kevin Wheelan, MD, chief of staff at Baylor Heart and Vascular Hospital in Dallas.

Although this method has been used to treat more than 9,000 patients worldwide, it is still considered investigational in the US. The maker of the device, Medtronic, Inc., of Minneapolis, plans to include data from this study in its submission for FDA approval.

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Peggy Noonan specializes in writing about health for consumers and medical professionals. She writes for leading national magazines and consumer publications as well as StopAfib.org.

Mellanie True Hills is founder and CEO of StopAfib.org and an atrial fibrillation survivor.