The Mayo Clinic has secured $48 million in grants from St. Jude Medical Inc. (STJ), a Johnson & Johnson (JNJ) subsidiary and a U.S. research institute for a major trial that could eventually spur more use of devices to treat a common heart-rhythm problem.

Atrial fibrillation, which involves disorderly heart beating that can heighten the risk of strokes, already represents a fast-expanding market for catheters that typically use heat to destroy tissue linked to the disorder. The market's growth profile, at more than 15% a year according to Morgan Stanley, has attracted medical-device companies such as Medtronic Inc. (MDT) seeking to offset slower growth in more mature markets.

Still, there hasn't been a large-scale study yet that clearly establishes the merits of device treatment in comparison with drugs, which remain the typical first-line treatment for atrial fibrillation.

Enter the "Cabana" trial, which will include 140 centers tracking 3,000 patients who will be split between treatment with so-called ablation catheters or drugs to control their heart rhythm for two to five years.

The study's main goal is to test whether using catheters to treat the disorder is better than drug therapy - which has been shown to have some drawbacks - in reducing mortality. The study will also track several other measures of safety and effectiveness.

Morgan Stanley analysts recently called Cabana a "landmark study" that could prove very meaningful for the atrial fibrillation market. Establishing devices as a first-line treatment for the disorder "has the potential to more than double the current annual ablation volume," they said.

Researchers are keeping the study "wide open" while they seek to answer tough questions, and either treatment method could look better, said Douglas Packer, a cardiologist at the Mayo Clinic and the Cabana study's principal investigator.

But he does see this as a landmark study that will help establish how patients with the heart disorder - which is the most common arrhythmia - are treated.

"I think that regardless of the outcome, the number of patients and the strength of the trial should have substantial impact of therapy," Packer said.

The catch is that it will take six years until results from Cabana, which will start enrolling patients in August, will be released. Morgan Stanley suggested interim results could come as early as 2011, but Packer said there is no plan to release data along the way.

Results from a small pilot study on 60 patients, used to help set parameters for the big study, could be released as early as August.

St. Jude is paying $20 million to fund Cabana while the National Heart, Lung, and Blood Institute is paying $18 million and J&J's Biosense Webster subsidiary is spending $10 million.

Both St. Jude and Biosense Webster have established catheter-ablation businesses. Biosense Webster became in February the first company to win Food and Drug Administration approval to specifically market ablation catheters to treat a certain type of atrial fibrillation. Before then treatment was done "off label" with catheters approved for other purposes.

Medtronic recently established itself as a big potential player by buying two small companies with devices under review, including one with technology that freezes tissue rather than burning it to disengage faulty signals.

-By Jon Kamp, Dow Jones Newswires; 617-654-6728; jon.kamp@dowjones.com