Stent Repair: Coated replacements better than radiation
Small mesh cylinders called stents, which doctors surgically implant to prop open clogged arteries, have a vexing tendency to become blocked soon after they’re inserted. Stents can be cleared, but the only approved treatment for keeping a bare-metal stent from clogging again is the application of radiation directly inside the blood vessel.
Two U.S. studies now find that inserting a new, drug-coated stent inside the old one—like a sleeve inside a sleeve—keeps blood flowing better than zapping it with radiation does.
In recent decades, millions of people with blocked coronary arteries have avoided heart-bypass surgery by undergoing angioplasty, in which a doctor inflates a balloon-tipped catheter in a blocked artery to clear the obstruction. But angioplasty is only a temporary fix in many patients. The U.S. Food and Drug Administration approved the insertion, after angioplasty, of bare-metal stents in 1994 and drug-coated stents in 2003.
The move to stents has paid dividends, but within a few months after they are implanted, about 20 percent of bare-metal stents clog. The blockages are made up of cells and proteins similar to those that form a scab, says cardiologist Gregg W. Stone of Columbia University Medical Center, a researcher in one of the new studies.
Radioactive pellets inserted into a bare-metal stent impede cell growth and can keep blood flowing through the vessel more consistently than angioplasty alone can. “But radiation is cumbersome to use and expensive,” says cardiologist David R. Holmes of the Mayo Clinic in Rochester, Minn., who coauthored the other study.
What’s more, radiation sometimes contributes to a blockage by exacerbating vessel damage at the edges of the stent, Stone says.
Subscribe to Science News
Get great science journalism, from the most trusted source, delivered to your doorstep.
Drug-coated stents discharge their cargo slowly over several weeks, the period when the vessel is still traumatized from angioplasty and at greatest risk of forming a clog inside the stent, says cardiologist David J. Moliterno of the University of Kentucky in Lexington, who didn’t participate in either of the new studies.
To compare the two treatments, the two research teams randomly assigned 780 people with blocked bare-metal stents to have angioplasty followed either by insertion of a second, coated stent or by radiation at the stent site.
The stent-in-stent approach proved better. Only 9 percent and 11 percent of stents laced with the drugs sirolimus (Rapamycin) and paclitaxel (Taxol), respectively, needed to be reopened during the two 9-month trials, the scientists report in the March 15 Journal of the American Medical Association. In patients receiving radiation, roughly twice as many stents required reopening during that time. The companies that make the two drug-coated stents sponsored the trials.
Coupled with earlier work, the new studies “establish the role of drug-[releasing] stents as the preferred treatment” for blocked bare-metal stents, says cardiologist Adnan Kastrati of the German Heart Center in Munich.
Some U.S. doctors are already using the stent-in-stent approach, Stone says.
In response to the new results, radiation treatment will probably fall into disuse, Stone and Holmes say.