Medtronic, Inc., announced Monday that its Mosaic bioprosthetic heart valves that were implanted 12 years ago in a pre-market approval trial are still working.

The artificial heart valves are designed to replace a diseased or damaged heart valve-usually the aortic or mitral valve. The device was approved by the U.S. Food and Drug Administration in 2000.

The patients in this prospective, nonrandomized trial were followed for 12 years at six international centers. The study involved 1,029 patients who had aortic valve replacement (AVR) and mitral valve replacement (MVR), and received the artificial valves between 1994 and 2000.

A study published in the Journal of Thoracic and Cardiovascular Surgery revealed a freedom from structural valve deterioration of 93.3 percent in AVR patients 60 years and older, and 95.3 percent in MVR patients 70 years and older. In addition, hemodynamic performance data showed stability up to 10 years, indicating durability of the Mosaic bioprosthesis over time.

“These strong findings address and support the intermediate- to long-term durability of the Medtronic Mosaic bioprosthesis in the aortic and mitral position,” Dr. Eric Jamieson, professor of surgery from the University of British Columbia in Vancouver and a principal investigator of the study since 1994, said in a statement. “I expect these results will be reviewed favorably by cardiothoracic surgeons, especially for patients 60 years of age and older requiring aortic valve replacement and patients 70 years of age and older who are candidates for mitral valve replacement.”

The third-generation valves are made of porcine (pig) tissue that is attached to a cloth-covered, flexible plastic stent, and was designed with technology that preserves tissues and mitigates calcium.

Medtronic is the world's largest medical device company, and Minnesota's seventh-largest public company based on revenue, which totaled $15.8 billion in its most recently completed fiscal year.