It is unlikely data from a big study backed by Boston Scientific Corp. (BSX) on using expensive implanted devices to help mildly symptomatic heart-failure patients will be ready for presentation at a cardiology conference this week, the company's chief executive said Tuesday.

The company had hoped results from the study, called Madit-CRT, would be ready for this week's Heart Rhythm Society conference in Boston, and industry participants and analysts are also watching closely for the results. But this is an event-driven trial that depends on patients having major problems or dying, so pinning down the timeline for completion and data presentation has been difficult.

"I'd have to say it's probably unlikely at this point," said CEO James Tobin, referring to the likelihood of releasing data this week, while speaking at a Bank of America health-care conference.

He said a data release could be a month or six weeks away, and that there wouldn't be a long delay.

Interest in the study is high because it has the potential to expand a market for implanted heart devices that has settled into a steady but unspectacular growth pattern. There is anticipation that results from the study of 1,820 patients will show benefits for treating patients with milder cases of heart failure with so-called cardiac resynchronization therapy, or CRT, devices.

These tools are approved today for use in patients with more severe heart failure, but Boston Scientific and rivals Medtronic Inc. (MDT) and St. Jude Medical Inc. (STJ) would very much like to expand the market. Madit-CRT focuses on whether the devices, which coordinate beating in erratic hearts, will help prevent death or heart-failure events compared with regular implanted defibrillators.

Because of this comparison, one key benefit for companies may be some patients who tend to get ordinary defibrillators today will be sent for more expensive CRT devices that also have defibrillators.

JPMorgan analyst Michael Weinstein said in a recent research note that Madit-CRT could represent the defibrillator market's first meaningfully positive catalyst since another key study came out about five years ago.

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