A U.S. government report found that more research is needed to determine the potential long-term benefits of using tissue-burning catheters to treat a common heart problem that represents a fast-growing market for medical-device companies.

Johnson & Johnson (JNJ), St. Jude Medical Inc. (STJ) and Medtronic Inc. (MDT) are among the competitors that either have or are establishing big businesses to treat atrial fibrillation with catheters. With an annual-growth profile of more than 15%, the market for addressing the heart-rhythm disorder has become very attractive to a sector looking to offset slower growth in other cardiology markets.

The growth has come, however, without deep evidence that using devices, rather than drugs, delivers favorable long-term results. The best method for treating the rhythm problem, which puts patients at risk for stroke, is among the top-priority targets for "comparative effectiveness" research called for by the Obama administration.

The new report examining evidence for device-based treatment came from the Agency for Healthcare Research and Quality. Looking at existing studies on radiofrequency ablation, in which heat delivered by catheters is used to burn tissue to cut off problematic electrical signals, the report found the procedure helps maintain normal heart rhythms for up to one year.

But the report found little evidence regarding long-term outcomes and said the impact of device-based treatment on avoiding strokes was unknown when compared with drugs. Additionally, there is thin evidence regarding the benefits of device treatment on quality of life, avoiding anti-coagulation medication or hospital readmissions, the report found.

"Radiofrequency holds promise for treating atrial fibrillation, but it is clear that more research is needed to demonstrate its potential long-term benefits," said Carolyn M. Clancy, director of the Agency for Healthcare Research and Quality, in a release. The agency is part of the U.S. Department of Health and Human Services.

"This report crystallizes the questions that researchers need to ask going forward," Clancy said.

The market for catheter-based treatment of atrial fibrillation took off without specific U.S. Food and Drug Administration approval because doctors can use devices cleared for other purposes in so-called off-label cases. J&J's Biosense Webster unit in February became the first company to win FDA approval to market catheter treatment specifically for the disorder based on results from a moderately sized study.

The industry has put money toward acquiring large-scale and long-term evidence to support use of the devices. The Mayo Clinic announced last month that it had secured $48 million in grants from St. Jude, Biosense Webster and the National Heart, Lung, and Blood Institute for a major study on the matter.

Called "Cabana," the study will include 3,000 patients to be monitored for years who will be treated with either catheters or drugs to control their heart rhythms. The study's main goal is to see whether catheters help reduce mortality, but it will also track several other measures of safety and effectiveness.

Atrial fibrillation is the most common type of arrhythmia, affecting more than 2.2 million Americans, and its prevalence increases with age, the Agency for Healthcare Research and Quality noted.

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