An 85-year-old Minneapolis woman lies on the operating room table at Abbott Northwestern ­Hospital and waits for the future of heart valve medicine.

The diseased aortic valve in Anna Schu’s chest is threatening her health, but she’s not a good candidate for open-heart surgery. So she’s decided to have an experimental procedure and become the first person in ­Minnesota to get a new device from Boston Scientific Corp. that is implanted through an incision in her leg to make it easier on her body.

The heart valve, in its compressed metal scaffold, represents the vanguard of a medical technology niche that experts say is poised to balloon to $4 billion in global sales five years from now. All of Minnesota’s major heart-device makers are developing or already selling such devices, and more than 150,000 have been implanted worldwide. And federal regulators are keeping close watch.

“There’s very high interest in this procedure,” said Tom Fleming, general manager for the structural heart business at Boston Scientific. “This technology is providing a good alternative to surgery.”

While Schu is under anesthesia, her surgeon dips the device in a surgical basin for a pre-implant soaking. Out of its sterile packing material, the gizmo looks like a short fishing rod with a small silver Slinky on the end.

It’s a catheter-delivered heart valve, requiring only a small incision in the leg to reach her heart. The doctor will snake the device in a hollow tube in the incision, through her femoral artery, through her circulatory system and over the great aortic arch, to within millimeters of her heart.

The procedure works. In a 30-minute operation, the doctor uses imaging that looks like an animated X-ray to guide the device over Schu’s existing aortic tissue and release it. A short burst of dye in her blood confirms the fit is tight and the valve doesn’t need to be repositioned.

Later that day, Schu says she’s feeling better than she expected, and hospital staff are telling Schu she looks good. Boston Scientific’s inaugural Minnesota patient is released from the hospital and goes on to become a positive mark in the device’s 30-day survival statistics.

The technique is called minimally invasive transcatheter aortic valve replacement, often known as TAVR or TAVI. It’s designed to treat aortic stenosis, which is a narrowing of the body’s largest artery, obstructing blood flow. The condition is often fatal within two years for patients showing ­symptoms.

By and large, TAVR today is approved only for very sick and often elderly patients. But the medical device industry predicts that the procedure’s safety profile will eventually get so good that patients will choose it even if they’re good candidates for traditional surgery. That spread into healthier patients is why analysts project robust growth in the next five years.

Today, implanting an artificial heart valve by cutting through the chest offers a more precise placement, and fewer valve leaks. About 2 percent of surgically implanted valves leak blood, compared with a range of 7 to 20 percent for the valves delivered on the end of a catheter like Schu’s, according to Dr. Wesley Pedersen, medical director for the heart valve program at Allina Health’s Minneapolis Heart Institute.

“That’s substantial. When it is a moderate leak, and probably even a mild leak, it negatively affects mortality,” said Pedersen, who is also Boston Scientific’s principal investigator for the trial. “As we go to get these valves to young, low-risk patients, we can’t tolerate stuff like that.”

Analysts project that the global TAVR market will surpass $4 billion in sales by 2020, up from about $1.5 billion today. As newer devices like Boston Scientific’s join already-approved progenitor devices from Medtronic and Edwards Lifesciences, executives and analysts will be watching closely to see if device prices fall. So far, they reportedly haven’t budged from the initial price of around $32,000, though the companies don’t disclose their prices.

Key players

Competition is heating up. Fridley’s Medtronic paid a $750 million TAVR patent-infringement settlement to California’s Edwards Lifesciences last year, and went on to capture about 40 percent of the TAVR market, driving 3 percent sales growth in its $737 million coronary and structural heart division in the most recent quarter. Boston Scientific is hoping to get Food and Drug Administration approval for commercial U.S. sales of the investigational device used on Schu, called the Lotus, by 2017.

St. Jude Medical Inc. in Little Canada, which has a 40-year history of making heart valves, hasn’t updated its FDA approval target since announcing last week that it had investigated unexpected early results and was working to restart its clinical trial for the Portico TAVR. All three companies’ devices are available commercially in Europe, and several other companies are working on their own TAVR innovations.

But recent experience with mass defects in defibrillator lead wires and metal artificial hips shows the risks of rapidly rolling out a new medical technology — especially when the device is designed to last inside the body for more years than researchers have been able to test it in humans.

On Sunday, Edwards is scheduled to present final results of the world’s first five-year survival data, during the annual meeting of the American College of Cardiology in San Diego. Edwards has been in the U.S. TAVR market longer than any company, since 2011. An earlier analysis of its five-year data documented a statistically significant survival benefit from Edwards’ Sapien device, but also a higher incidence of stroke compared to a control group.

The federal government sees a need for close monitoring of TAVR patients. In 2012, the Centers for Medicare and Medicaid mandated that U.S. TAVR patients be included in a registry that tracks outcomes like death, stroke, heart attacks and quality of life, to see whether patients in the real world have as good outcomes as the patients in the clinical studies. The registry is supposed to answer how well the devices perform after five years, and whether patients with less risk in traditional open-chest surgery are being slipped into the TAVR ­population.

Last week the Journal of the American Medical Association published the first one-year mortality data from the registry and Medicare records, concluding that 12,000 patients from 2011 to 2013 had an overall mortality rate of 24 percent. Four percent of the patients experienced stroke after having the procedure.

Physicians said the findings seemed to confirm data in smaller prior studies that implanting aortic valves on the end of a catheter is at least as safe as doing the procedure by cutting open the chest. The median age of high-risk patients in the TAVR registry study was 84.

“There are some patients when, having seen this data, they say, gosh, I want this TAVR. … Let’s go for it. There are other patients who will look at it and will say, you know, I’m doing OK, I’m just going to hold off for now,” said Dr. David Holmes Jr., a Mayo Clinic interventional cardiologist who was the study’s lead author.

“Somebody who is 95 might say, looking at this data, ‘Gee, I’m not so interested in that,’ ” Holmes said. “Or they might say, ‘I’d rather have the procedure so that I don’t have to come back into the hospital again. I may not live any longer, but my quality of life is better.’ ”

No matter how individual decisions break down, the industry is prepping for a long run selling the catheter-delivered gadgets. As many as 30 percent of patients with severe aortic stenosis had been doing without any surgical treatment before TAVR, Holmes said, and the number of Americans in their 70s, 80s and 90s is ­rapidly growing.

The industry’s strong interest will be on full display Sunday in San Diego, where at least seven academic papers on catheter-delivered valve therapies will be presented in the cardiology conference’s “late-breaking” sessions for academic papers deemed potentially newsworthy. That’s one of the largest number of papers for any therapy.

The high interest also is evident in the profusion of marketing claims streaming out of the manufacturers’ PR departments, trying to draw even the narrowest distinctions among their products.

One key selling point for TAVR devices is whether they can be repositioned if the team doing the procedure doesn’t like the initial fit. Each company is deploying in its own linguistic jujitsu to emphasize how its device provides the most flexibility. Other subtle differences among the devices include the diameter of the delivery catheter, the way the devices are deployed in the heart, and the way that they attach to existing tissue.

For Minnesota valve-replacement patient Elnora Scheffler, factors like small differences in design aren’t what she was focusing on.

Scheffler, an 85-year-old resident of Morton said she couldn’t believe how easy and painless it was to have a valve implanted via catheter. She’d heard stories of relatives and friends who’ve had open-heart surgery and were left with pain and broken ribs, but she felt none of that.

“I was amazed,” she said. “It was almost hard to believe that I had something done. For all I know about people who have had heart problems and heart surgeries, I didn’t even feel like I had the right to talk about it, because it was so un-Earth-shaking.”