NEW ORLEANS — Cardiologists are reporting a major advance: A long-awaited study suggests that many people with a bad aortic valve, the heart’s main gate, can avoid open-heart surgery and have a new one placed through a tube in an artery instead.

There is a downside — a higher risk of stroke — and uncertainty about how long these valves will last.

Still, doctors predicted that if the new valve wins federal approval, patients would embrace it as they did balloon angioplasty, which has allowed millions to have clogged arteries fixed without an operation.

“The fact that it’s not open-heart surgery sells itself, and the rest gets lost in the mix,” said Dr. Craig Smith, heart surgery chief at Columbia University and New York-Presbyterian Hospital.

He led the study and gave results Sunday at an American College of Cardiology conference in New Orleans.

Dr. Michael Crawford, chairman of the meeting and cardiology chief at the University of California, San Francisco, called it “a historic event” that would dramatically change practice. “As good as surgery is, patients just don’t want it,” he said.

The aortic valve can stiffen and narrow with age, making the heart strain to push blood through it. Severe cases are treated with surgery to replace the valve, but that’s risky for many older people who have this problem. Without an operation, half die within two years.

The study tested a way to wedge in a new valve without surgery. Dr. Edward McNulty, a cardiologist at the University of California, San Francisco, explained how it works:

Through an artery in the groin or the chest, “a new heart valve is literally crimped on a balloon and advanced across the narrowed, older, diseased heart valve. The balloon is inflated and the new valve left in place.”

A test of this gentler approach in people too sick for surgery found it greatly improved survival, doctors reported last fall. The new study involved nearly 700 people eligible but at high risk for surgery.

Their median age was 84, and they were randomly assigned to get valves replaced through surgery or the new way. Here’s how much people dread this operation: 28 people withdrew from the study or refused treatment once they found out they had been placed in the surgery group.

In the end, both groups did very well.

After one year, about 24 percent of the artery patients and 27 percent of the surgery patients had died — comparable results in a study this size and considerably fewer than researchers had predicted.

However, strokes and other neurological problems were twice as common in the artery-treated group — 8 percent versus 4 percent. Previous studies also have found more strokes with the artery approach.

Other complications were a trade-off: Major bleeding and new cases of a fluttering heartbeat called atrial fibrillation were more common after surgery; there were more blood-vessel problems with the artery approach.

Leakage was more common with the new-style valve, too, though doctors said that problem can get better with time. “It will take longer to figure that out,” Smith said.

The valve’s maker, Edwards Lifesciences Corp. of Irvine, Calif., paid for the study, and some researchers consult for the company. Edwards is seeking federal approval to sell the valve for inoperable patients now and plans to ask the same for less ill patients like those in the new study in a few months.

The company plans to charge $30,000 for the valve, which is already used in Europe.