Stents don’t work? A look back at the research
In 2020, hospitals placed more than 45,000 coronary stents in Medicare patients that met criteria for overuse, a recent report from the Lown Institute Hospitals Index finds. Coronary stents were the most overused service by volume of the eight measured, and were provided unnecessarily even at some of the most prestigious hospitals in the country.
Coronary stenting or balloon angoplasty (known as percutaneous coronary intervention or “PCI”) for stable heart disease has long been considered an indicator of overuse, because many years of evidence shows that PCI doesn’t provide benefits to patients beyond medication therapy. However, some hospitals disagree, saying their stents are appropriate.
What’s the evidence behind PCI, and why do hospitals keep doing these procedures? We revisit this issue with a look back at research and interviews over last few years to give you the answers.
Dr. Lown’s example
The practice of placing a stent or balloon into patients’ arteries to open up blockages started in Switzerland in 1977 when Dr. Andreas Grüntzig first performed this intervention. This procedure quickly became the standard of care for treating heart attack patients and saved countless lives.
Soon, PCI became more popular for treating patients not having heart attacks, but for patients with stable heart disease as well. The assumption was that unblocking arteries would prevent a future heart attack or stroke, just as unblocking a clogged pipe prevents it from bursting. However, there was little evidence to support this theory.
As PCI became widespread, cardiologists like Dr. Bernard Lown recognized that they were widely overused and put patients at unnecessary risk of harm. As Dr. Lown wrote, his team took a conservative approach, avoiding PCI and the coronary artery imaging that typically leads to these interventions. Instead they treated risk factors, prescribed medications when necessary, recommended lifestyle changes, and discussed stress. Over 35 years, their clinic saw about a thousand patients scheduled for surgeries looking for a second opinion; fewer than 30% of patients were referred for PCI. Their published work showed a low rate of cardiac events and mortality for patients managed conservatively.
Do stents for stable heart disease work?
Dr. Lown’s experiment showed that many patients with stable heart disease could be managed without surgery and avoid poor outcomes. This finding would later be validated in multiple randomized trials. See the following timeline of trials of PCI compared to medical therapy:
As early as 1983, the Coronary Artery Surgery Study (CASS) showed no mortality benefit of coronary artery bypass surgery (a precursor to PCI) compared to medical treatment, putting in question the “clogged pipe” theory of heart disease.
Early trials show no mortality benefit for PCI
Eleven randomized trials including 2,950 patients are done between 1987 and 2001, evaluating PCI compared to medical therapy. A 2005 meta-analysis of these trials showed no mortality benefit or difference in cardiac events for PCI, except for patients who recently had a heart attack. At this time, PCI was still seen to be effective for reducing angina (chest pain).
COURAGE study puts PCI to the test
This large trial of 2287 patients found that PCI in addition to medical therapy did not reduce all-cause mortality, heart attack, or hospitalization for heart disease compared to medical therapy alone.
Prior to COURAGE, fewer than 3000 patients had been included in PCI trials, and trials had not incorporated modern stents and medication management standards.
The benefits of PCI over medical therapy remain controversial, with competing studies finding different results. While one meta-analysis found a long-term mortality benefit to PCI and another study found a benefit for patients with reduced blood flow to the heart, other trials once again found no benefit to PCI particularly when compared to modern medical therapies.
ORBITA Trial breaks new ground
The ORBITA trial tested PCI for the first time against medical therapy plus a “sham” procedure, in which patients believed they were getting a stent but nothing was inserted. The results showed not only that PCI did not have a mortality benefit but also that it did not improve chest pain. The authors experience backlash from cardiologists contesting their findings.
ISCHEMIA Trial validates conservative approach
ISCHEMIA is the largest study to date measuring the effect of stents and bypass surgery on patients with stable coronary artery disease. Given previous studies showing a potential PCI benefit for people with reduced blood flow, this trial looked at the impact of PCI for people with severely reduced blood flow. The results showed no difference in risk of heart attack or death compared to drug therapy, even for patients with severe ischemia.
Why do we still put in stents?
Despite trial after trial showing a lack of benefit, why are these invasive cardiac procedures still common for patients with stable heart disease? These trial findings go against the intuitive idea that arteries with plaque are like a “clogged pipe” and that opening blocked arteries prevents heart attacks and death. In fact, it’s not a single blocked artery, but the presence of plaque throughout the coronary system (known as atherosclerotic plaque burden) that is most dangerous. Opening up an artery only treats the symptom of the disease; plaque buildup in the arteries is best ameliorated with lifestyle changes and medical therapy.
As Louisville cardiologist Dr. John Mandrola wrote about the ISCHEMIA trial in Medscape, it is hard to disabuse the clogged pipe analogy because it fits so well with how we believe our bodies should work. “While part of our brains can understand the data, another part of our brain cannot unsee the gnarliness of a severely stenosed coronary artery,” he wrote.
It’s also difficult for cardiologists to change their practices when they want to do something to improve their patients’ condition. “It’s hard to think that the procedure we were trained to do for so many years doesn’t actually help patients,” said Dr. David L. Brown, professor of medicine at Washington University of St. Louis, in response to the ORBITA trial. “But if cardiologists look at the evidence objectively and with an open mind, that should be all it takes for them to make changes in how they talk to patients about the issue,” he said.
We also can’t ignore the financial incentives behind cardiac interventions. Clinicians are paid much more for doing surgical interventions than they are for consulting patients on lifestyle changes. When you add the financial reward on top of the belief that they are helping patients “that’s the methamphetamine of being a physician, it’s very mentally addictive,” said Dr. Vinay Prasad, Associate Professor in the Department of Epidemiology and Biostatistics at the University of California San Francisco. Even when faced with new evidence about an intervention, it’s difficult to sway doctors’ views. “Smart people are very good at coming up with reasons why the new study doesn’t apply to them,” said Prasad.