Use of Coated Stents on the Rise, But How Safe Are They?Jul 16, 2008 | Parker Waichman LLP
Experts disagree on whether stent science is moving too fast and doctors are concerned that blood clots can form at the site of drug-coated stents long after implantation. Now, it seems, drug-coated heart stent implantation is on the rise. Last month, 73 percent of all stent procedures in the U.S. used a coated stent, up from 62 percent in December, the lowest level in several years. The figures came from Goodroe Data Warehouse unit of VHA Inc., of Irving, Texas, and were based on a survey of 60 U.S. hospitals.
Coated stents accounted for the vast majority—approximately 88 percent—of the U.S. stent market about two years ago; however, in 2006, some studies sparked controversy in the stent market and suggested coated stents could result in reclogging and the formation of often-deadly clots years after implantation. Because of this, revised guidelines from medical societies and proposals by the Food and Drug Administration (FDA) to improve standards on future stents were prompted and coated stent sales tumbled through 2006 and 2007. This decline worsened when a study was released in March 2007 that questioned the efficacy of stents versus drug therapy.
Stents are tiny wire-mesh tubes that prop open arteries once doctors clear them of blockages. Some stents have a drug coating meant to keep vessels from re-clogging following balloon angioplasty procedures. Bare-metal stents tend to re-clog more often than drug-coated stents, so physicians are quick use drug-coated stents, even in those patients with complex heart disease, not the patients in whom the devices were tested. In either case, stents are implanted to maintain arterial blood flow. About one million Americans are implanted with stents annually with the most elaborate models costing about $2,000; uncoated, bare-metal stents, sell for less than half that.
Scar tissue causes stents to re-close in about one in five patients, who then require a follow-up procedure to remove and replace the device. Without the procedure, the patient can suffer a heart attack, said Dr. Laura Mauri, an assistant professor of medicine at Harvard Medical School and Brigham and Women's Hospital, in Boston. Drug-coated stents, which were approved by the FDA in 2003, work to prevent too much scar tissue from forming; however, research indicates that the drug can increase the risk of too little scar tissue forming and a blood clot appearing in the stent. "If not enough scar tissue forms to cover the stent, the metal can create a blood clot on its own," said Dr. Jack Tu, a senior scientist at Canada's Institute for Clinical Evaluative Sciences and a professor with the University of Toronto. "It's a fine balance. You want some scar tissue to form around the stent, but you don't want too much to form.
"People initially had a wave of shock" over the safety concerns, said William O'Neill, a cardiologist at the University of Miami medical school. Some doctors advise stent patients to take anti-clotting drugs indefinitely, or at least until more is known about the clotting risk, compared with J&J's initial recommendation of only three months.