Stent heart devices from Abbott Laboratories (ABT) and Medtronic Inc. (MDT) outperformed an older device from Boston Scientific Corp. (BSX) in three-year data from two studies by better helping patients avoid serious events, Abbott and Medtronic said Monday.

Abbott and Medtronic each released fresh study details during the Transcatheter Cardiovascular Therapeutics conference in San Francisco. The data came from separate, company-funded studies that the companies used to win approval for their drug-coated stents in the U.S. last year. The scaffolds for heart arteries use medication to fight renarrowing and comprise a roughly $4 billion global market.

Abbott's Xience stent leads the domestic market behind solid study data, and Medtronic has been working to improve modest sales for its Endeavor stent by highlighting the device's long-term safety profile.

In both studies released Monday, the companies measured their devices against the Taxus Express stent from Boston Scientific that formerly led in the U.S. and has since been replaced by a newer version called Taxus Liberte. Abbott and Medtronic have argued that their studies remain relevant, however, because of similarities between the newer and older Boston Scientific devices.

The Spirit III study for Abbott's Xience stent has previously shown Xience outperforming the Boston Scientific device on certain fronts, including a composite measurement of serious events including death and heart attacks.

In the three-year data from the 1,002-patient study, Abbott's stent had a 9.1% rate of so-called major adverse cardiac events, compared with a 15.7% rate for Taxus Express, Abbott said. In addition to cardiac death and heart attacks, that composite measurement includes retreatment of the same area in the affected artery.

On another combined measure of events called target lesion failure, the rate was 8.3% with Xience and 14.4% with the Boston Scientific stent, Abbott said.

The company also noted that Xience had no additional cases of late-developing, stent-related clots in the study between years two and three.

The rise of Xience has both helped and hurt Boston Scientific. While its Taxus device lost the market lead, Boston Scientific has maintained a strong position because it also sells the Xience stent under the name Promus and a profit sharing deal with Abbott.

Abbott cited market-share estimates for July from an outside firm that show Xience and Promus holding more than half the U.S. market combined. Taxus Liberte is next at 20%, followed by a Johnson & Johnson (JNJ) stent and Medtronic's Endeavor.

Endeavor's share has been squeezed by the popularity of Xience and Promus, but also the perception created by some earlier study data that Endeavor isn't a strong performer when it comes to avoiding renarrowing that can lead to repeat procedures to clear heart arteries.

The fresh evidence from Medtronic's 1,548-patient Endeavor IV study doesn't show a difference between Endeavor and Taxus Express at three years on measures of retreatment. But it does show fewer late-developing clots for Endeavor between years one and three, and this fuels a finding of fewer heart attacks with the Medtronic stent at three years, the company said.

Medtronic also noted better performance for Endeavor on a combined measure of death due to heart events and heart attacks.

Avoiding rare but potentially deadly clots that develop after a year became a serious concern in the coated-stent market after evidence arose three years ago about the dangers of such developments. While clotting worries have since eased, the need to keep coated-stent patients on long courses of anti-clotting drugs has kept doctors from using those devices in many cases.

In the Endeavor IV study, Endeavor had more cases of clots through 360 days than Boston Scientific's stent. But there was one case among Endeavor patients between 360 days and 1,080 days, and 11 cases among Taxus Express patients in that span.

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