AF occurs when the heart’s two upper chambers (the atria) quiver instead of beating effectively. In paroxysmal AF, the abnormal heart rhythm starts and stops on its own.

When drugs to control erratic heartbeats don’t work, doctors may use electric shock or thread catheters through blood vessels to zap cardiac cells with heat, a therapy called radiofrequency ablation.

The innovative therapy reported at the American College of Cardiology (ACC) 2010 Scientific Sessions utilizes freezing technology, or cryoablation, instead.

“Cryoablation could offer a straightforward and significantly simplified treatment for patients with very symptomatic and obnoxious atrial fibrillation,” says Dr. Douglas Packer, professor of Medicine at the Mayo Clinic in Rochester, Minnesota, and principal investigator of the Stop AF (Sustained Treatment of Paroxysmal Atrial Fibrillation) study.

In the pivotal trial, the Arctic Front Cardiac CryoAblation Catheter System from Medtronic kept nearly 70 percent of AF sufferers symptom-free for one year, compared to 7.3 percent of those given the usual drug therapy.

“There are 150,000 to 200,000 new cases of AF in the U.S. every year, Dr. Packer explained to Post editors. “Some will be asymptomatic and treated with blood thinners to prevent strokes. Others might be treated with anti-arrhythmic drugs. But the target population for ablation is people who don’t respond to drug therapy—and there are a lot of them.”

To date, more than 9,000 patients have been treated worldwide with the Arctic Front Cryocatheter. The treatment is not yet approved in the U.S., however.

“Seeking FDA approval for the system is the next step,” says Dr. Packer. “Data from Europe support the approach, but the FDA requires a large U.S. trial to demonstrate the device’s effectiveness and safety,” he explains. “This is the hallmark clinical trial in the U.S.”

Other ACC News on Atrial Fibrillation

Ablation therapy: Dr. Packer also reports that the CABANA pilot study of 60 patients with persistent or long-standing AF and underlying cardiovascular disease found that catheter ablation more effectively prevented recurrent AF than drug therapy. But the NIH-funded study is just getting started.

“The 4 to 5 year Cabana trial will consider longer-term issues of ablation: Does it reduce mortality, does it prevent strokes, and how much does it cost,” notes Packer.

Drug therapy: Analysis of pooled data from the EURIDIS and ADONIS trials suggest that it’s safe for doctors to prescribe dronedarone (brand name: Multaq) for their patients with atrial fibrillation within two days after discontinuing treatment with the drug amiodarone (brand name: Cordarone).

“Many doctors want to switch their AF patients from amiodarone to dronedarone,” says Dr. Peter Kowey, lead investigator and chief of the division of cardiovascular diseases at the Main Line Health System in Wynnewood, Pennsylvania. “These data will give some guidance until a randomized trial is completed.”

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