Stent studies don't reflect “real world” patients

April 10, 2011 - 0:0

NEW YORK (Reuters Health) -- Stroke-preventing devices are not being tested in people who resemble the patients most likely to receive them, a new study shows.

The researchers looked at tests being done as part of “post-market surveillance studies,” which test products that are already approved and in general use by the public.
They found that patients who had small mesh tubes, called stents, placed into their neck in these studies were healthier than other patients in a broader nationwide registry of people who received stents.
“We were surprised,” said Dr. Robert Yeh, the lead author of the study and a cardiologist at Massachusetts General Hospital and Harvard Medical School.
The “intention and presumption of most post-marketing studies is that they represent the group of patients that we see in clinical practice.”
Yet the patients in the larger registry database who weren't in the post-marketing studies were 50 percent more likely to have had a stroke in the past, and were four times as likely to die in the hospital, Yeh said.
“When we look at these results (from post-marketing surveillance) we should be a little bit careful in applying them to the patient in front of us,” Yeh told Reuters Health.
People in the study were having a stent put into a major blood vessel in the neck that had become narrowed, to widen it and prevent plaque from moving into the brain and causing a stroke.
The blood vessel is known as the carotid artery. When carotid artery stents were first approved, the Food and Drug Administration required that companies monitor their safety and effectiveness after they came on the market.
Like stents that are placed in heart arteries, carotid artery stents are implanted through an incision in the skin - usually in the groin -- without surgery.
Yeh and his colleagues looked at the health characteristics before and after stenting for 7,115 patients in the national registry; roughly half of them participated in surveillance studies. They found that four of every 10 patients in the surveillance studies had experienced a stroke or mini-stroke before they had the stent.
In contrast, six of every 10 patients who were not involved in any studies had had a stroke or mini-stroke (also called a transient ischemic attack, or a TIA).
Surveillance study participants were also less likely to have had any symptoms of stroke at the time of their stent procedure. “There's a reasonable explanation for that,” said Dr. William Gray, a cardiologist at Columbia University Medical Center and New York-Presbyterian Hospital, who has conducted post-market studies of stents. He was not involved in this study.
Gray said it all comes down to insurance; Medicare, in particular. Medicare, the federally-funded health insurance for people over age 65, pays for stenting when people have symptoms.
When people don't have stroke symptoms, they are more likely to enroll in studies - such as post-marketing surveillance -- that will cover the costs of the procedure, Gray told Reuters Health. Yeh agreed that insurance could partially explain the differences, but he thinks it doesn't explain them all.
The risk of dying 2 years after stenting was also 20 percent lower among patients in the post-marketing studies than among people in the larger registry who didn't enroll in a study.
Yeh said that difference might be explained by the skills of the physicians performing the stenting procedures for post-marketing studies.
“Maybe physicians are paying more attention,” Yeh told Reuters Health.
Or, it could be that studies exclude sicker patients, because people need to be well enough to sign and read papers and consent to joining the study, Yeh said. The authors write that post-marketing surveillance studies “may be insufficient for monitoring long-term, community-based outcomes,” and that nationwide registries might be better able to fill that role.
The study, published in the journal Circulation, was funded by the American College of Cardiology Foundation, which developed the national database, or registry, of carotid artery stent procedures.
The Food and Drug Administration and Boston Scientific - a company that makes carotid artery stents -- did not respond to requests for comment.
Another stent maker, Abbott, said in an email to Reuters Health, the “company is supportive of clinical registries as they contribute to the overall body of data on product use and provide additional data that help physicians treat their patients,” but would not comment on the study.
When the carotid artery becomes clogged, another option for widening it is to have surgery to remove the plaque. Doctors have debated the benefits of carotid artery stents versus surgery. Neither procedure is ideal. People who have surgery are more likely to later have a heart attack, while those who undergo stenting are more likely to suffer a stroke later on (see Reuters report, October 11, 2010).