New Type of Stent Shows Promise
TUESDAY Nov. 11, 2008 -- A new generation of stents shows promise in avoiding the late-onset problems that have plagued drug-eluting stents in patients with heart disease, researchers say.
The tiny mesh tubes that are stents are intended to prop open narrowed arteries, but this new stent works in a novel way. It is coated with an antibody that provokes cells lining artery walls to migrate to and cover the stent, thus speeding the healing process and keeping arteries open longer.
"This is kind of the third-generation stent. One could even call these 'smart' or 'smarter' stents, because they are designed to deal with some of the problems that have existed in the earlier versions," said Dr. Gregory Dehmer, professor of internal medicine at Texas A&M Health Science Center College of Medicine and director of the cardiology division at Scott & White in Temple. "It's an exciting development, but . . . we have to temper our enthusiasm with the growing knowledge that some of the problems with drug-eluting [emitting] stents didn't show up for two to three years."
Even with continued promising results, the new device is likely years away from the U.S. market. "The FDA has largely taken a position of making companies repeat their studies here in the U.S.," said Dr. John P. Reilly, an interventional cardiologist and director of cardiovascular CT at Ochsner Health System in New Orleans. "It will probably be three years before the technology comes to the U.S."
The findings come from two European studies expected to be presented Tuesday and Wednesday at the annual scientific meeting of the American Heart Association, held this year in New Orleans.
Stents are used in patients undergoing angioplasty procedures to reopen narrowed arteries. Bare metal stents were the first to be introduced, but patients often had to undergo repeat procedures.
Drug-eluting stents, coated with slow-release drugs to prevent the vessel from closing up again, came next. But these also had limitations, namely late-stent thrombosis, or stent-related blood clots.
"The drug-eluting stents are doing exactly what they were designed to do, which is inhibit the excessive tissue growth after the injury from the balloon angioplasty or bare metal stent platelet, and they are doing it well," Dehmer said. "The problem is that, at the same time, they are also inhibiting the normal healing response, or the cell growth that covers up the metal stent drugs and incorporates it into the vessel wall."
The new stent is known as an "endothelial progenitor cell-capturing" (EPC) stent. As their name implies, endothelial progenitor cells are those that have the ability to differentiate into endothelial cells, or those cells that line the walls of the arteries.
The first study, by German researchers at Muller Hospital Munich, presented data on 1,640 "real world" patients, mean age almost 63 years old. One-quarter of the patients were diabetic, two-thirds had high blood pressure, one-quarter were current smokers, and more than one-third had had a prior heart attack.
Almost 74 percent of the participants received statin drugs (which include Crestor, Lipitor or Zocor) prior to stenting. This family of cholesterol-lowering drugs also stimulates the number of endothelial progenitor cells in the blood.
At one year, only 1 percent of participants receiving the new stent had experienced a stent-related blood clot, 5.4 percent needed a revascularization on the same artery, and 5.1 percent underwent a catheter-based procedure to restore blood flow.
Just over 9 percent had a major adverse cardiac event such as a heart attack, unanticipated bypass surgery, or death. Just over 2 percent of patients died of cardiac causes, 1.8 percent of which were heart attacks.
The second study involved 236 patients at the Academic Medical Center of the University of Amsterdam in the Netherlands. All were treated with the EPC stent. The average age here was 65.
Three patients (1.2 percent) suffered stent thrombosis, and 10.2 percent required a repeat revascularization procedure of the same vessel.
Almost 14 percent suffered a major adverse cardiac event (2.5 percent of all patients had a heart attack), and 3 percent died, 0.8 percent of cardiac causes.
According to the study authors, these numbers were as good or better than those for drug-eluting stents.
One expert was encouraged by the findings.
"Earlier work indicated this line of investigation might be fruitful, but the magnitude of benefit with EPC-capturing stents in this study is a little surprising," said Dr. Kirk Garratt, clinical director of interventional cardiovascular research at Lenox Hill Hospital in New York City. "The target lesion revascularization (TLR) rates ran about 5 percent, even for diabetics, which is at least as low as we've seen with drug-eluting stents. The ongoing work with higher-risk patient groups is also very encouraging. It's looking like EPC-capturing stents might be an excellent alternative to drug-eluting stents, and will only require a short course of dual antiplatelet drugs."
And Garratt was impressed by the device's safety profile, as well. "Of the several biological approaches under study to improve coronary stent results, this approach is among the most benign," he said. "It doesn't involve potent cellular or genetic manipulations that could have unexpected consequences. In that regard, this should be a safer approach."
The U.S. Food and Drug Administration has more on stents.
Posted: November 2008