A Medtronic Inc. (NYSE:MDT) stent graft system for treatment of aneurysms that occur in the aorta has successfully met primary endpoints through 12 months of a clinical trial, according to the company.

In the VALOR II study of 160 patients at 24 U.S. medical centers the Valiant thoracic stent graft system showed a 97 percent success rate for treating aneurysms through 12 months, the company said.

The overall mortality rate was 12.6 percent with 3.3 percent of the patients having died of “aneurysm-related” causes.

The primary and secondary endpoints of the study were defined as “the absence of (a) aneurysm growth (>5 mm) at one and 12 months, and (b) type I and/or type III endoleak for which a secondary procedure was performed or recommended at or before the 12-month visit,” according to the company.

The results of the study were presented at a clinical trials session at the annual meeting of the Society for Vascular Surgery in Chicago.

A thoracic aortic aneurysm occurs when an artery wall in the aorta weakens, causing the wall to expand or bulge as blood is pumped through it. About 15,000 people in the U.S. die from the aneurysms every year, according to data from the Cleveland Clinic.

MDT already has Conformite Europeenne (CE) Mark approval for the Valiant Captivia Thoracic stent graft system in the European Union, where the product has been available since mid-2010. Medtronic’s cardiovascular businessbrought in $8.54 billion to the company in 2010, essentially flat compared to the previous year.