Aortic stenosis is primarily a problem for the elderly: In developed countries such as the United States and Canada, about 3 percent of those over age 75 will develop the dangerous heart valve disease. With an aging U.S. population, that creates some urgency to expand treatment options and better understand the risks and benefits of those treatments.

Enter a team of researchers from New York-Presbyterian/Columbia University Medical Center and other institutions in the United States and Canada. Last April, the group published results from a definitive trial: For average-risk patients, a less invasive valve replacement procedure using a catheter was just as effective and safe as surgery to replace a faulty valve.

“We even saw suggestions of superiority,” said Martin Leon, M.D., co-author of the study and director of the Center for Interventional Vascular Therapy at New York-Presbyterian/Columbia University.

The American Heart Association named the study, published in the New England Journal of Medicine, one of the top 10 heart and stroke science advances of 2016.

The aortic valve connects the heart and the aorta, the large blood vessel that carries blood from the heart. In aortic stenosis, the opening of the aortic valve narrows over time, restricting blood flow and often eventually damaging the heart itself. The narrowing may occur because of scarring and calcium buildup in the flaps of the heart valve — or, in rare younger patients, it can be caused by a malformation of the valve itself.

Conventionally, surgeons have sewn in a new heart valve — either metal or from a human, cow or pig donor — during open-heart surgery. But some patients are not healthy enough to undergo such an invasive procedure.

So in the early 2000s, interventional cardiologists began testing novel devices that could be threaded into place via catheters inserted through a small incision in the leg or chest. The so-called transcatheters are tipped with an inflatable balloon and expandable new valve. The cardiologist can push the old valve wide open and place the new one inside, then expand it to fit.

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At first, the procedure — dubbed transcatheter aortic valve replacement, or TAVR — was associated with frequent, serious complications, including stroke and the need for a pacemaker. The first clinical trials of TAVR’s effectiveness were conducted in people with severe aortic stenosis who were at high risk of not making it through open-heart surgery, often because they were frail or had other serious illnesses such as advanced lung or kidney disease. A 2010 study found that TAVR was a good alternative for patients who were poor candidates for open-heart surgery.

Since then, improvements in TAVR devices and their use by interventional cardiologists and surgeons have been “remarkable,” said Craig Smith, M.D., co-author of the recent study and surgeon-in-chief at New York-Presbyterian/Columbia University. Even for patients who were candidates for surgery, interventional cardiologists began to use TAVR. But the medical community lacked research-based evidence that such choices were warranted.

Now they have it.

In the recent study, researchers evaluated outcomes for more than 2,000 patients in nearly 60 surgical centers in the United States and Canada. Patients were randomly assigned to TAVR or open-heart surgery to replace damaged valves, and the team followed them for two years, evaluating the rate of deaths from any cause and disabling strokes.

There was no significant difference between the two groups. About 19 percent of patients in the TAVR group died or had a disabling stroke compared with about 21 percent in the surgery group. Plus, researchers reported another important finding: Patients who had catheters threaded through an incision in the leg were less likely to die or suffer a disabling stroke than those with catheters inserted through the chest.

They also found that TAVR caused fewer cases of kidney damage and life-threatening bleeding.

Today, TAVR is essentially the standard-of-care for severe aortic valve stenosis and patients at high surgical risk, Leon said, and insurance companies almost always cover it. Average-risk patients should talk with their doctors about whether the option is right for them, he said.

Interventional cardiologist Laura Mauri, M.D., of Brigham and Women’s Hospital in Boston, said TAVR is “now a good treatment option available for many more patients.” But, she cautioned, “it will be particularly important to evaluate the long-term results for these catheter-based valves as they begin to replace surgical techniques for valve replacement in appropriate patients.”

The jury’s still out for patients at low risk for surgery complications. But Leon and his colleagues are now enrolling low-risk patients in a study to test TAVR versus surgery. Results are expected in a few years.

Editor’s note: This is one in a 10-part series of the top medical research advances of 2016 as determined by the American Heart Association.