Medtronic Inc. on Monday became the second company allowed to sell a technology in the U.S. that helps repair the hearts of tens of thousands of patients each year who are considered too ill or too frail for open-heart surgery.

The Food and Drug Administration approved the sale of Medtronic's self-expanding transcatheter CoreValve system for people with narrowing of the aortic valve in the heart. The approval came months earlier than expected, without the Fridley company having to go before an independent review panel. Medtronic was allowed to enter the market based on the strength of its clinical trials alone.

Approval had been expected in April. But Medtronic said its tests showed that CoreValve is "safe and effective with high rates of survival and some of the lowest rates of stroke and valve leakage reported." The FDA apparently agreed.

"It's a new day. For those of us who manage these patients, we just could not offer them these options before," said Dr. John Liddicoat, president of Medtronic's structural heart business. "To have lifesaving therapy to offer these patients, that is very rewarding. And the scale is astounding. A lot of people are going to benefit."

Liddicoat said about 550,000 people worldwide are diagnosed each year with aortic valve stenosis, a dangerous and often-fatal narrowing of the aortic valve. About 100,000 to 150,000 of those are in the U.S. Half of patients with aortic valve stenosis die within two years of diagnosis, and about 30,000 patients each year are considered too ill to risk open-heart surgery, the most common way to replace a diseased aortic valve.

CoreValve replaces the aortic valve without doctors cracking open a patient's chest. A catheter is snaked up into the heart through a vein in the leg or a small incision in the chest and a new valve is deployed over the old one. Recovery takes days, rather than weeks or months after open heart surgery.

Until Friday, Edwards Lifesciences of Irvine, Calif., was the only company with an approved transcatheter aortic valve in the United States — the Sapien valve. Medtronic and Edwards have been competing in Europe for several years.

At the same time, the companies also have been locked in a number of patent disputes over the device. Earlier this week, Edwards won a patent ruling against Medtronic in a Delaware federal court. An earlier Edwards patent victory in Europe was set aside, and Medtronic was allowed to resume sales there. That fight hasn't kept CoreValve from the market, however.

Dr. Jeff Popma, an interventional cardiologist who was a co-principal investigator for CoreValve's medical trials across the country, said: "I think that the commercial availability of the CoreValve is going to make a tremendous impact on patients' lives in the United States."

The FDA approved four different CoreValve sizes. That means 90 to 95 percent of patients in the extreme-risk group "can be treated in this way now," said Popma, who is on staff at Beth Israel Deaconess Medical Center and at Harvard Medical School in Boston. "There is tremendous physician interest in having the CoreValve available," he said.

Dr. Wes Pedersen, director of transcatheter valve therapies at the Minneapolis Heart Institute Foundation and a cardiologist at Abbott Northwestern's Minneapolis Heart Institute, has implanted the Edwards valve in nearly 140 patients. The valves are different, he said, and it may take some time for doctors trained on the Sapien valve to become proficient with CoreValve. But the CoreValve, he said, is a little easier to reposition if necessary.

"That gives you a little more comfort, so you can go back and move it if you need to," he said, adding that he welcomes the additional choice for a wider array of patients.

Medtronic officials said Friday that it will take time for the CoreValve to be widely available, with initial availability at the 45 centers that participated in clinical trials. It could take years before physicians across the country are fully trained in how to implant the device.

In a note to investors, Larry Biegelsen of Wells Fargo said the earlier approval could boost Medtronic's 2014 sales by $25 million to $50 million in a U.S. market worth $500 million this year. Joshua Jennings of Cowen said the earlier approval would help Medtronic ramp up sales and training more quickly and lead to a stronger 2015.

But Danielle Antalffy of Leerink Swann Research told investors that much will depend on how quickly Edwards' next-generation valve wins approval from the FDA, guessing that will happen in the next few months. She expects 2014 will end with Edwards continuing to control about 65 percent of the transcatheter aortic valve market.

James Walsh • 612-673-7428