One-year data from a large study showed an Abbott Laboratories (ABT) heart stent again outperformed an older device from Boston Scientific Corp. (BSX) by leading to lower rates of serious events, adding to evidence that has helped make Abbott's device a market leader.

The 3,690-patient, Abbott-sponsored "Spirit IV" trial showed similar performance between the Abbott and Boston Scientific stents among a subgroup of diabetic patients. However, the study has set the table for Boston Scientific to defend its turf among a patient group it has targeted. Data from the study 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. Abbott and Boston Scientific are big competitors, although they 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 deal, good data for Xience can help or hurt Boston Scientific depending on how it affects sales of its different stents. The company's home-grown Taxus-brand stents, which were matched up against Xience in the Spirit IV trial, are more profitable for the company.

Specifically, Spirit IV showed Xience topping Taxus Express, an older device Boston Scientific has essentially replaced with a new version called Taxus Liberte. Abbott believes the study results remain relevant because the Boston Scientific stents are similar. Boston Scientific, however, argued that Liberte is better than the older version on certain fronts - data released on Tuesday showed benefits for the newer version in small arteries and long areas needing treatment, for example.

Whether stent-implanting doctors will shift business due to the Spirit IV study, which Abbott believes is possible, remains to be seen.

The study 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 patients treated with Xience 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 did not 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.

The results come two days after Abbott released a three-year update from its Spirit III study measuring Xience against Taxus Express. That study, which helped Abbott gain access to the U.S. market where Xience supplanted Taxus as the top-selling stent, also showed superior Xience performance.

Because nearly a third of patients in the bigger Spirit IV study are diabetics - a group that Boston Scientific in particular has targeted - results for this group were highly anticipated.

On the diabetes front, the rates of events were similar between the two stents despite the Xience advantages among non-diabetics. The 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.

Cardiologist Gregg Stone, the study's main investigator, noted that diabetics tend to have smaller vessels that are prone to re-clogging. Stone, who serves on both the Abbott and Boston Scientific advisory boards, is a professor of medicine at Columbia University Medical Center.

He 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