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Drug Coated Stent Debate Yet to be Resolved

May 12, 2008 | Parker Waichman Alonso LLP

Experts continue to disagree on the usefulness and safety of drug coated stents.   Stents are an important element in heart-disease treatment.  Tiny wire-mesh tubes, stents 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.

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.  New stents approved by the U.S. Food and Drug Administration (FDA) in 2003 are drug-coated 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."

In December, the FDA announced that it is preparing to issue new drug-coated stent testing requirements.  The revised rules are expected to be more stringent and to specify the numbers of patients on whom new drug-coated stents can be tested and for how long.  The rules also offer a recommended length of time patients should take anti-clotting drugs following implantation.

Drug-coated stents are recommended for patients with an increased risk of suffering from reclosure, Tu said, such as those with diabetes, smaller-than-normal blood vessels, or long lesions left by heart disease.  Drug-coated stents have been quite successful in preventing repeat procedures, Mauri said and, “have medication on them.  The medicine releases slowly over time and prevents cells from building up that could lead to a blockage."  But, even those who favor drug-coated stents note that they have risks, such as that medications must be taken with them—a strict regimen of anti-clotting medications for at least one year following the procedure.  "Patents who are unable to comply with this regimen should be treated with bare-metal stent implantation," said Dr. Murtuza J. Ali, an interventional cardiology fellow at the Boston University Medical Center.   If the patient isn't diligent about taking the anti-clotting drugs, a heart attack could result over time, Mauri said.  "We know if these medicines are stopped early, there are risks of blood clots forming inside the stent," she said.