Study raises doubts about drug-coated heart stents

BARCELONA, Spain — Experts have expressed concerns that drug-coated heart stents — metal-mesh tubes used to prop open coronary arteries — may in rare instances lead to potentially fatal blood clots.

Studies released Sunday at the World Cardiology Congress in Barcelona raised new concerns about the risks that may accompany the drug-coated stents, which were introduced in 2000 as an improvement on bare-metal stents.

Nearly 6 million people worldwide now have the drug-lined versions. The devices are intended to keep arteries open after they're cleared of fatty deposits and are often credited with saving patients from future heart attacks or bypass surgery.

A Swiss-Dutch study tracked 8,146 patients and found that recipients of drug-coated stents were at increased risk of thrombosis, or blood clots, that can occasionally result in death.

Two other Swiss studies, analyses of presented and published information discussed at the cardiology conference, also found that first-generation drug-coated stents had higher links to thrombosis compared to bare metal stents.

In bare metal stents, heart cells naturally grow to cover the stent, providing a natural biological lining. But in the drug-coated versions, the drugs prevent tissue growth — which is both their intent and their possible downfall.

Drug-coated stents were previously viewed as a great advance since the drugs they emitted prevented cells that could block the arteries from growing. A thick growth of cells is undesirable, but a thin layer of cells lining the artery is essential. In some instances, drug-coated stents have prevented this minimal protective cell layer from growing, leaving exposed metal, which essentially can act as a clot magnet.

"This is potentially explosive information," said Dr. Steven Nissen, president of the American College of Cardiology and director of cardiology at the Cleveland Clinic.

"It certainly makes me pause with substantial concern," said Nissen. He said there is already a shift in the U.S. away from using drug-coated stents in favor of their uncoated predecessors.

Doubts about drug-coated stents were initially raised in March by a small-scale Swiss study, though there have long been naysayers about their potential adverse effects. Results from the Swiss-Dutch study found that the incidence of thrombosis does not diminish as time passes.