Secondary mitral regurgitation (MR) can be a serious complication of heart failure — in a recent study, two-thirds of the people who were taking the maximum recommended doses of drugs for severe forms of the disease were hospitalized or dead within two years.

But researchers at a widely watched medical device conference in San Diego said this past weekend that when a similarly sized group of patients had a MitraClip heart device made by Abbott Laboratories implanted, the rate of hospitalization and death dropped to 46 percent. Abbott's "Coapt" trial, which included patients at several Minnesota hospitals, was described as giving doctors a long-sought way to treat secondary MR.

The stock market greeted the news by sending Abbott shares up more than 3 percent, closing at $71.44 on Monday. Abbott officials said Monday that the Coapt study results show promise.

"Patients had fewer heart failure hospitalizations, a reduction in risk of death, and quality of life was improved. These are all things that are really important to patients," Barathi Sethuraman, divisional vice president of clinical affairs in Abbott's structural heart business, said Monday from the annual Transcatheter Cardiovascular Therapies (TCT) symposium of the Cardiovascular Research Foundation.

"Transcatheter" refers to medical devices that can be put in the body without surgery. Typically, these minimally invasive devices are folded inside catheters and then inserted into the diseased heart or blood vessel using live X-rays to navigate. The medical team unfurls the heart valve, stent or other device, then withdraws the delivery catheter from the puncture site in the leg or wrist.

Abbott's MitraClip has been approved in the United States since 2013 as a minimally invasive treatment for primary MR, which happens when the mitral valve itself becomes diseased and allows blood to flow backward in the heart.

Doctors have been using the MitraClip experimentally to treat secondary MR, which occurs when blood flows backward through the mitral valve. This happens when the heart's overall shape has changed as part of advanced heart failure, which distorts how the valve's leaflets open and close.

For cases using one device, the MitraClip secures the valve's leaflets near the center, in effect creating two smaller valves — one on each side of the clip — that continue to open and close with a better seal, so that blood only moves in the intended direction through the heart. (The average number of clips used in the study was 1.7 per patient.)

Abbott Labs intends to file its application with the Food and Drug Administration (FDA) by the end of the year to market the device for secondary MR, Sethuraman said.

The Coapt study, published in the New England Journal of Medicine at the same time the results were published at TCT, says 614 patients at 78 hospitals in the United States and Canada were randomized between 2012 and 2017 to get either MitraClip plus medical therapy, or traditional medical therapy alone. The patients had at least moderate to severe secondary MR, and their left ventricles pumping only 20 to 50 percent of the blood it was supposed to, even though they remained on the maximum recommended dose of drugs throughout the trial.

MitraClips were implanted in 287 of the 293 people for whom it was attempted during the trial. Two years later, the MitraClip patients had an annualized hospitalization rate of 36 percent for heart failure, compared to 68 percent for the control group of 312 people. Death from any cause was 29 percent in the MitraClip group and 46 percent in the control arm.

The trial was sponsored by Abbott. Sethuraman said the study researchers felt the results came out so strongly in favor of the MitraClip that they would no longer feel comfortable randomizing secondary MR patients to medical therapy alone.

"There is an option for these patients now," Sethuraman said.

She acknowledged that patients were carefully screened to meet strict eligibility criteria for the trial. Dr. Ian Meredith, chief medical officer for competitor Boston Scientific Corp., said during a conference call with investors on Monday that Abbott had "threaded the needle" in patient selection, and it remained to be seen how mitral clipping will perform down the road.

But Meredith congratulated Abbott on the study, saying it was a "great day" for functional MR patients seeking "thoughtfully designed" strategies to repair mitral valves instead of implanting artificial ones. (Earlier this year, Boston Scientific announced a $90 million investment in a mitral-valve repair company called Millipede, whose transcatheter annuloplasty ring is still in development.)

"Is it unethical to treat patients with MR medically? No. This is one trial," Meredith added.

About 10 percent of Americans age 75 or older — about 4 million — have one of the forms of mitral regurgitation. Abbott doesn't release device prices, but the New York Times reported Monday that the device costs about $30,000, which does not include costs for the hospital or medical team.