A study of 200 heart patients in the United Kingdom shocked the international cardiology community on Thursday when it reported that patients who had stents put in to treat nonemergency chest pain showed about the same improvements as patients who got a "sham" placebo procedure.
The findings from the first-of-its-kind study contradicted widespread assumptions that using the metal mesh tubes to prop open clogged arteries would allow patients to walk longer on a treadmill by hastening blood flow to the muscles that make the heart pump. Cardiologists said the study is likely to cut down on the use of stents, affecting Minnesotans with chest pain and the Minnesota companies that make stents, including Medtronic.
Several companies with major operations in Minnesota are key manufacturers of stents, including Medtronic, Boston Scientific and Abbott Laboratories. Medtronic stock dropped nearly 3 percent Thursday, while Boston Scientific dropped 1.5 percent and Abbott Labs rose half a percent.
The study didn't disclose which companies' stents were used in the trial.
The peer-reviewed study, published Thursday in the medical journal Lancet, found that patients with stable chest pain who got a stent could tolerate running on a treadmill for an extra 28 seconds, on average, six weeks after the procedure. Patients who got a placebo procedure, but no stent, improved their treadmill tolerance by 12 seconds after six weeks. The difference was statistically insignificant.
"I think this is a game-changer," said Dr. Rita Redberg, a researcher and cardiologist at the University of California, San Francisco, who was not involved in the research. If the study doesn't result in fewer stents being placed, "I think we have some real explaining to do."
However, doctors were quick to note that the study doesn't change the thinking about the use of stents in medical emergencies. Most stents are placed in patients with unstable blockages or who have had heart attacks, whereas the Lancet study focused on stent placements in patients with stable blockages but episodic chest pain, or "angina."
"If you're having a heart attack, a stent is lifesaving," said Dr. Michael Miedema, a preventive cardiologist with the Minneapolis Heart Institute at Abbott Northwestern Hospital. "That hasn't changed at all."
The study report noted that some patients may still choose to have a stent placed for nonemergency chest pain, rather than taking prescription drugs to treat their stable angina.
Questions about study
A spokesman for Abbott Labs in Minnesota said the study population had "very mild" disease and was not reflective of patients who typically get stents placed. More than 25 percent of the patients who got stents in the trial would not have had one implanted under current medical guidelines.
The Society for Cardiovascular Angiography and Interventions, a not-for-profit trade group for interventional cardiologists, also questioned "the conclusions of this study."
"SCAI has long stood by the conviction, based on abundant clinical evidence, that PCI is the preferred treatment for cardiac patients who need more than medicines to improve their health and quality of life," the society stated in a news release.
(PCI stands for "percutaneous coronary intervention," the medical term for a minimally invasive stent procedure.)
Stents are widely used — or overused, according to some critics — to treat chest pain and blood flow problems that happen when arteries that supply blood to the heart muscle become blocked with a waxy buildup called plaque.
To place a stent, an interventional cardiologist inserts a thin tube into a puncture site, often in the groin area, and then advances the narrow device into the blood vessels on the heart. Often a tiny medical-grade balloon at the end of the tube is inflated to push aside the plaque, and then the metal mesh tube is expanded to hold the vessel open.
In many cases, the stent is coated with a drug designed to fight inflammation and prevent the vessel from re-closing. Prices for "drug-eluting" stents vary depending on the model sold and the purchasing power of the hospital buying it. In 2015, hospitals in the U.S. paid an average price of about $1,300 for a stent, which was a 10 percent decline from two years earlier, according to purchasing data from the ECRI Institute in Pennsylvania.
Doctors perform more than 500,000 stenting procedures worldwide each year for the relief of angina.
In the study published Thursday, physicians at five hospitals in the United Kingdom took 196 patients who had at least a 70 percent blockage in a single coronary artery and randomized them to get either a real stent placed or a "sham" procedure that mimicked stent placement but left no device in the body. The patients were not told which group they were in until after six weeks.
"PCI did not improve exercise time beyond the effect of the placebo," the study authors wrote. "This result might seem to contradict the real-world experience that patients report relief of angina after PCI. However, real-world data inevitably mix physical effects with placebo effects. Forgetting this point, or denying it, causes overestimation of the physical effect."
SCAI, the interventional cardiologists' group, said the number of patients in the study was "very small," which undercut its ability to offer conclusive findings. Also, using a person's tolerance for treadmill exercise is an imprecise and subjective measure, the organization said.
Miedema said doctors were already becoming more conservative in using stents for nonemergency cases, and that this study will accelerate that trend. In some ways, it will give doctors extra muscle when trying to convince patients that they should try taking prescription drugs before stents.
" 'I have this big blockage and you're just going to leave it alone? You're not going to do anything about it?!' That's the way that they phrase it," he said. "This study makes [medical management] more of a defensible treatment plan."
Dr. M. Nicholas Burke, director of cardiovascular lab operations at the Minneapolis Heart Institute, called the results "surprising" and "disappointing" and said they should challenge doctors to review how they use stents. They should also rely on blood flow readings inside arteries, rather than patients' complaints and symptoms, to determine the best candidates for stents.
"It's not that stents were bad," he said. "It's just that we're probably using them too much and we're not being perhaps as specific about who gets them. I think that we can do better and this study shows us that we need to do better."