One-year data from two studies showed an Abbott Laboratories (ABT) heart stent outperformed both newer and older versions of Boston Scientific Corp. (BSX) devices by leading to lower rates of serious events, adding to evidence that has helped make Abbott's stent a market leader.

When it came to a subgroup of diabetic patients, however, the 3,690-patient, Abbott-sponsored "Spirit IV" trial showed similar performance between the Abbott and older Boston Scientific stents. This sets the table for Boston Scientific to defend its turf among a big patient group it has targeted.

Data from Spirit IV and the other trial, called "Compare," were released Wednesday at the Transcatheter Cardiovascular Therapeutics conference in San Francisco.

The devices at issue are drug-coated stents, which prop open clogged heart arteries and use medication to combat renarrowing. They make up a roughly $4 billion global market where Abbott and Boston Scientific are big competitors.

The companies also share some business because Boston Scientific sells the Abbott-made Xience device under a different name and a profit-sharing deal. Because of that arrangement, good data for Xience can help or hurt Boston Scientific depending on how it affects sales of its different stents.

Spirit IV showed Xience topping Taxus Express, an older device Boston Scientific has essentially replaced with a new version called Taxus Liberte. Boston Scientific argued that Liberte is better than the older stents on certain fronts; data released on Tuesday showed benefits for Liberte in small arteries and long areas needing treatment, for example.

But Abbott believes Spirit IV results remain relevant because the Boston Scientific stents are similar. Abbott's case was bolstered by the single-hospital, 1,800-patient Compare study from the Netherlands that represented the first big match-up between Xience and Liberte, and similarly showed better Xience performance.

Whether stent-implanting doctors will shift business due to the two studies, which Abbott believes is possible, remains to be seen. Cardiologist Gregg Stone, Spirit IV's main investigator, said Wednesday that he views Xience as the top stent for nondiabetics. He serves on both Abbott and Boston Scientific advisory boards.

Spirit IV included twice as many patients with Xience devices as Taxus Express stents. The main measurement was a combination of death from heart events, heart attacks linked to the problem artery, and retreatment of the problem area due to restricted blood flow. On this composite measurement, known as target lesion failure, the rate at one year for Xience patients was 4.2%, while it was 6.8% with Taxus Express.

On the specific measure of retreatment in the problem area, the rate was 2.5% with Xience and 4.6% with Taxus Express. Notably, this study didn't include routine patient follow-up with angiogram imaging tests - doctors believe this can fuel repeat procedures due to narrowing they see, but isn't causing discomfort.

The study also showed a lower rate of rare but dangerous stent-related clots, which are a closely watched complication, with the Xience device at one year.

Compare's main goal, meantime, was to track a combination of serious events including death, nonfatal heart attacks and retreatment of the previously treated artery. On this measure, the rate for Xience at one year was 6.2%, compared with a 9.1% rate for Taxus Liberte.

Unlike clinical trials that hand-pick patients and may omit certain complications, Compare tracked patients with a variety of "real-world" problems.

Xience's dominance in Wednesday's data stopped when it came to diabetics, who tend to have smaller vessels that are prone to re-clogging.

Among diabetic patients in Spirit IV, who made up nearly one-third of the study, the rates of events were similar between Xience and Taxus Express despite the Xience advantages among nondiabetics.

That study "actually supports Boston Scientific in relation to the diabetic outcome, even though we're using our last-generation stent," said Keith Dawkins, the associate chief medical officer at Boston Scientific, in an interview. The company said late Wednesday it was reviewing the results from Compare.

Stone, a professor of medicine at Columbia University Medical Center, said outcomes for diabetics can still be improved and should be an area of focus for future drugs and stents.

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