UPDATE 2-Medtronic atrial fibrillation system shines in study
* Trial meets main goals
* Cryoablation seen superior to anti-arrhythmic drugs
* Procedure nearly 10 times more effective
* Pilot also showed ablation worked better than drugs
* Medtronic shares up 3.7 pct (Wraps in small pilot study, adds share move)
ATLANTA, March 15 (Reuters) - A noninvasive procedure that freezes and kills problem-causing heart tissue was nearly 10 times better at eliminating a potentially serious heart rhythm disorder than conventional anti-arrhythmic drugs, researchers said on Monday.
A clinical trial of Medtronic Inc's (MDT.N) cryoablation system looked at 245 patients with paroxysmal atrial fibrillation, a condition marked by intermittent episodes of abnormal heart rhythm that causes the upper chambers of the heart to quiver.
A small pilot study funded by St. Jude Medical Inc (STJ.N) compared the two therapies in a sicker population of patients and also found that the procedure worked better than drugs.
Atrial fibrillation is the most common heart disorder, affecting 2.2 million Americans and 10 million people worldwide. It significantly raises the risk of stroke.
Patients in the Medtronic-sponsored trial who underwent the cryoablation procedure -- which involves using a catheter to freeze away the heart tissue where the problem originates -- was just as safe as drugs used to treat the condition and far more effective, meeting the study's primary goal of eliminating atrial fibrillation one year after the procedure.
Dubbed Stop-af, the Medtronic trial showed that almost 70 percent of patients who had cryoablation remained free of the condition after one year, compared with just 7 percent of patients who received drug therapy, according to data presented at the American College of Cardiology meeting in Atlanta.
"This is the best data we have at this point in support of cryoablation (to treat atrial fibrillation)," said Dr. Douglas Packer of Mayo Clinic, the lead investigator of the study.
Over 3 percent of patients treated by cryoablation experienced a serious condition -- a narrowing of the pulmonary vein in 7 out of 228 patients, one of whom required another procedure to widen the vein.
Damage or irritation to the nerve that controls the diaphragm was reported in 11 percent of the cryoablation procedures, but none of the cases was considered serious, with 98 percent resolved by the 12-month follow-up.
Complications related to the atrial fibrillation itself were also monitored. During the follow-up period, 97 percent of patients who got the procedure and 92 percent of the drug therapy patients did not suffer heart attack, stroke or death.
Less than 1 percent of patients treated with cryoablation were hospitalized for a recurrence of the disease, compared with 6 percent in the drug group.
Patients in the pilot study had advanced atrial fibrillation and tended to have other medical problems, such as high blood pressure, diabetes or coronary artery disease,
Packer, who also led the pilot study, dubbed Cabana, acknowledged that the main limitation of this study was its small size, but said it lays the foundation for a larger one.
He said the larger study, which will include 180 centers, is currently enrolling patients.
Anti-arrhythmic drugs eliminate atrial fibrillation in about half of all patients but can have adverse side effects.
Cryoablation is an alternative that is growing in popularity. Over the past decade, more patients have been referred for ablation procedures when drugs proved ineffective.
Catheter ablation involves inserting a thin tube into a blood vessel, usually through a site in the upper leg or neck, and then threading it though the body until it reaches the heart. When it reaches the area of the heart that causes abnormal rhythms, the tissue is ablated, or destroyed.
The procedure has been used to treat arrhythmias for years. The U.S. Food and Drug Administration initially cleared ablation catheters to treat arrhythmias, such as atrial flutter, but not atrial fibrillation.
Only Johnson & Johnson (JNJ.N) has an ablation device approved by U.S. health regulators specifically to treat atrial fibrillation.
The Medtronic device, which the company added to its portfolio with the 2008 acquisition of CryoCath, has been approved in Europe and Australia.
Medtronic shares were up 3.7 percent to $45.55 in late-morning trading on the New York Stock Exchange. (Reporting by Debra Sherman and Bill Berkrot; Editing by Derek Caney and John Wallace)