To experts and analysts, the only thing keeping trancatheter aortic valve replacement (TAVR) from eventually replacing open heart surgery — even for low-risk, younger patients — is whether the valves last as long and perform as well as those implanted in open heart surgery.

On Saturday, Medtronic announced that its Corevalve system, in which a new aortic valve is implanted with a catheter inserted through an artery in the leg, showed better results than replacing the valve surgically. Medtronic's study evaluated patients considered high risk for surgery.

The head-to-head study found an all-cause mortality rate of 14.2 percent in Corevalve patients after a year, compared with 19.1 percent in patients who had their valves surgically replaced.

"Our key finding that TAVR with Corevalve was associated with a significantly higher rate of survival at one year in patients at increased risk has significant and broad implications," said Dr. David H. Adams, chair of the Department of Cardiothoracic Surgery at the Mount Sinai Hospital in New York City and national co-principal investigator of the Corevalve U.S. Pivotal Trial.

Adams presented the study data at a meeting of the American College of Cardiology in Washington, D.C.

The U.S. Food and Drug Administration in Janurary approved the use of Corevalve in patients considered extreme risk for open heart surgery — those considered too ill to risk the operation. It has not yet been approved for use in high-risk patients, although FDA approval is expected later this year.

Aortic valve stenosis is a dangerous narrowing of the aortic valve that prevents the aorta from properly opening and closing and restricts blood flow to the rest of the body. An estimated 300,000 people worldwide suffer from it. As many as half of those with aortic stenosis die within a year. Yet, one-third of those with the disease are deemed to be in danger of dying during open heart surgery.

Still, TAVR is limited in the United States for patients considered too old or frail to survive open heart surgery. Lowering the bar to a high-risk group would significantly increase the number of patients for whom TAVR — and Corevalve — could be used. The advantage to TAVR comes not only in a shorter, less-invasive procedure, but with a much faster recovery for patients. The trend worldwide is to broaden the net of patients for whom TAVR is an option.

Medtronic's valve, which received European approval in 2007, has been implanted in more than 50,000 patients worldwide. Edwards Lifesciences is currently the only other company approved to sell a transcatheter aortic valve, the Sapien valve, in the country.

According to Adams, the Medtronic study also showed low stroke rates in patients with Corevalve — about the same as with open heart surgery — and a significant improvement in patients' quality of life.

"The results of the High Risk study confirm our findings in the Extreme Risk Study, namely that careful pre-procedural planning with CT-based determination of valve sizing and attention to 'best practice' implantation techniques result in a strong hemodynamic performance of the self-expanding Corevalve with low rates of one year paravalvular regurgitation and stroke," said Dr. Jeffrey J. Popma, director of Interventional Cardiology at the Beth Israel Deaconess Medical Center in Boston and national co-principal investigator of the Corevalve trial.

The High Risk study involved 747 patients who had a predicted risk of dying up to a month after surgery of 15 percent. The average age of patients in the study was 83.2 years old, and the study enrolled a nearly equal number of men and women.

"The results of the Corevalve High Risk Study effectively demonstrate the value of the heart team approach, with an equal number of cardiac surgeons and interventionalists generating the compelling clinical outcomes," said Dr. John Liddicoat, senior vice president at Medtronic and president of its Structural Heart Business.

In an interview, Adams said this is the first time TAVR has been deemed "superior" to traditional open heart surgery. He said it will be "interesting" to see how the Corevalve's performance impacts future use of the technology.

"I think its going to open the door to continued study of lower risk groups," he said, adding that the FDA will want more information. However, he said, "Our data is going to accelerate the march towards lower risk patients."