The device, approved by the Food and Drug Administration (FDA), is called the Medtronic CoreValve System.
On March 28, Loyola University Medical Center became the first Illinois hospital to implant the device in a patient who was not part of a clinical trial.
The new device is deployed with a catheter, which is inserted in an artery in the groin and guided up to the heart.
Once in place, the artificial valve takes over the function of a diseased valve. The system is much less invasive than traditional open-heart surgery.
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The study found that patients who received the device had significantly lower mortality than heart valve patients who underwent open-heart surgery.
"This is a major breakthrough," said Fred Leya, co-principal investigator at the Loyola site, along with Mamdouh Bakhos.
The study, published in the New England Journal of Medicine, included 795 seriously ill heart-valve patients who were randomly assigned to receive the new device or to undergo open-heart surgery.
After one year, the mortality rate was 19.1 per cent in the group that underwent open-heart surgery, but only 14.2 per cent in the group that received the new device.
At the one-year mark, quality-of-life scores increased 23.2 points in the device group and 21.9 points in the open-heart surgery group.
Quality of life is measured on a 100-point scale, in which 5 points is considered important and 20 points is considered a very large improvement.
Aortic stenosis occurs when the heart's aortic valve is narrowed, restricting blood flow from the heart to the body. The valve doesn't open properly, forcing the heart to work harder to pump blood.
Aortic stenosis can lead to heart failure and death, researchers said.
The FDA approved the device in January 2014 to treat patients with severe aortic stenosis who are too ill or frail to have their aortic valves replaced through open-heart surgery.
Such patients have a nearly 50 per cent risk of death at the one-year mark unless they are treated.