BY AMERICAN HEART ASSOCIATION NEWS
Editor’s note: This is one in a 10-part series of the top medical research advances as determined by American Heart Association volunteer and staff leaders.
For the nearly half a million Americans each year who need stents to hold open clogged or damaged heart arteries, a new class of dissolving devices is beginning to pass clinical trial hurdles, raising the possibility of use in the coming years.
In Europe, two such “bioresorbable” stents are commercially available, both tiny tubes, or “scaffolds,” made of polymers that slowly dissolve away within a few years after surgery: Abbott Vascular’s Absorb and Elixir Medical’s DESolve.
In theory, the experimental dissolvable devices may overcome some serious, long-term problems associated with today’s metallic stents. Among those problems: The permanent presence of a metal stent prevents a vessel from flexing in response to normal physical changes, which can damage the vessel over time, and an accelerated form of atherosclerosis inside the stents can cause them to fail.
According to several studies published this year, Abbott’s Absorb, a dissolving stent that slowly releases the drug everolimus, performed nearly as well or just as well as its metal drug-releasing counterpart.
“The fact that the outcomes are nearly the same is impressive given that this is really a first-generation technology that has been rigorously compared to the best-in-class metallic drug-eluting stent,” said Gregg Stone, M.D., an investigator on two of the trials. Stone is a professor of medicine at Columbia University and a research director at New York Presbyterian Hospital/Columbia University Medical Center.
Still, in each study, the dissolving heart stent failed to show broad or significant superiority over a conventional drug-eluting stent.
In the ABSORB III study reported in the New England Journal of Medicine in November, patients with angina were slightly more likely to develop a clot near the insertion site if they had the Absorb stent (1.5 percent versus 0.7 percent).
Researchers in the ABSORB II trial, reported in The Lancet in January, found that patients with restricted blood flow and lesions in the arteries of the heart who were given Absorb were less likely to have new or worsening angina (22 percent compared with 30 percent), but dealt with more heart attacks (4 percent compared with 1 percent).
“Saying they’re comparable is probably not enough for me,” said Ashvin Pande, M.D., director of invasive cardiology at Boston Medical Center.
BMC was one of many clinical trial sites for the Absorb studies, so Pande and his colleagues have been using the bioresorbable scaffolds for more than a year. Even so, it’s not clear yet that the new devices are better than their trusted, tested counterparts, he said. And Pande is especially concerned about the slightly higher rates of thrombosis with bioresorbable scaffolds.
With time and physician experience, those rates might drop, Pande said. He and his colleagues will also know if the new devices can minimize some of the longer-term issues they were designed for, such as the limited vessel motility of metallic stents.
“I think patients like the idea that this is going to go in there and fade away over time,” Pande said. “But really, is it going to make a clinical difference? I think it’s too early to say.”
When metallic stents were first coming into use, results were similarly “suboptimal,” Stone said. It takes doctors time to get used to techniques for implanting new devices, and time to learn which patients are most likely to benefit.
“The results will only improve over time,” Stone said.
Photo courtesy of Abbott