Medtronic Incorporated's AneuRx stent graft system, used to prevent rupturing of swollen vessels that supply blood to the abdomen, is linked to more deaths than open surgery for the same purpose, U.S. regulators said.

The risk of death from an aneurysm increases each year after getting the AneuRx implant, reaching 1.5 percent after five years, according to a public health notice posted on the Food and Drug Administration's website Tuesday. That's "substantially higher" than the 0.18 percent average annual mortality rate with standard surgical repair, the agency said.

The FDA has been reviewing the safety of AneuRx since side effects and deaths prompted the agency to issue public health notices in 2001 and 2003 about the risks for patients with life-threatening abdominal aortic aneurysms, or AAA. Medtronic, of Minneapolis, said the data are skewed by poor follow-up, patients refusing treatment and an elderly patient population.

"Based on the highest-quality data available, AneuRx performs better compared to open surgery in late AAA-related deaths," company spokesman Daniel Beach said Tuesday in an e-mail. The FDA's analysis relies on average mortality risk from surgery rather than a controlled clinical study, Beach said.

AneuRx is the only product of its kind on the U.S. market that has been used in a significant number of patients with five years of follow-up data, the FDA said. The agency still recommends using it if surgery poses special risks because of inexperienced doctors or patients' age or health complications.

Stents are a minimally invasive alternative to surgical repair of the abdominal aorta, a large vessel that supplies blood to the abdomen, pelvis and legs. An estimated 1.2 million people in the U.S. have abdominal aortic aneurysms. Only about 15 percent are ever diagnosed and half of these are never treated, according to Medtronic.

Medtronic rose 95 cents, or 2 percent, to close at $48.34 on Tuesday.