Drug-releasing stents are more effective than bare metal stents at keeping a blocked artery open after angioplasty, but the difference does not result in fewer deaths or subsequent heart attacks after the procedure, according to a review of recent studies.
However, the evidence shows that drug-releasing stents "did decrease the number of times a patient had to be re-treated for a blockage of the blood vessel or the stent," said Janette Greenhalgh, a research fellow at the University of Liverpool who led the review.
The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.
Angioplasty with stent placement is a procedure performed on people who have a buildup of fatty material inside the blood vessels that supply the heart. During the procedure, surgeons inflate a small balloon in the vessel to compact the fatty material against the vessel wall and widen its diameter. Then, "a tubular mesh scaffold called a stent is placed inside the vessel wall to help it remain open," said Greenhalgh.
In some cases, the vessel begins to narrow again and the patient must undergo another procedure. Some stents contain drugs that inhibit cell growth and inflammation. The stent releases drug slowly to prevent this narrowing.
Re-narrowing is a common problem in angioplasty patients treated with stents, occurring "between 20 and 50 percent of the time, depending on size, location and the complexity of the lesion" that caused the original blockage, Greenhalgh said.
Greenhalgh and her colleagues reviewed data from more than 14,500 patients, whose average ages ranged from 57 to 70, in 47 carefully controlled studies comparing the use of drug-releasing stents to bare metal stents.
The studies included 10 different types of drugs used in the drug-releasing stents, but the most widely used drugs were an anti-inflammatory drug called sirolimus and a chemotherapy drug called paclitaxel. Of the 47 studies, pharmaceutical companies funded 65 percent, in part at least.
Since bare metal and drug releasing stents have a similar track record when it comes to death and other major coronary complications "and drug-releasing stents are significantly more expensive," said Greenhalgh, it might not be cost-effective to prescribe the more expensive drug-releasing stents.
One economic review conducted in the United Kingdom suggested that drug-releasing stents might be better for patients with the highest risks of requiring re-intervention and might be cost-effective in only a small percentage of such patients.
Some patients who receive stents take an anti-clotting drug for a period after stent placement. In 2006, several studies appeared suggesting that patients with the drug-releasing stents might be at greater risk for developing blood clots, and groups like the American Heart Association recommended that these patients stay on anti-clotting drugs for up to a year.
Patients might consider this factor when deciding on the type of stent they will receive.
"One important question that we ask our patients before doing this procedure is 'Do you have any planned procedures that it's important for you to get done before we put this drug stent in?'" said Alan Yeung, M.D., an interventional cardiologist at Stanford University Medical Center.
If a patient has multiple surgeries on the horizon, Yeung said, they might not be a good candidate for a drug-releasing stent simply because they might need to take an anti-clotting drug for much longer than with a bare metal stent.