Medicated stent raises safety concerns

Drug-coated stents have fallen under the suspicion of safety concerns when Swiss-Dutch experts at the World Cardiology Congress (WCC) in Barcelona presented their study, depicting recipients of drug-coated stents were at increased risk of potentially-fatal thrombosis (formation of a blood clot (thrombus) in the heart or artery).

A drug-coated or medicated stent is a tiny, expandable mesh-like metal cylinder, coated with medicine that decreases scar formation on the stent, and fits over an uninflated angioplasty balloon. These stents are used to open up a coronary (heart) blood vessel that is narrowed or blocked by plaque build-up (atherosclerosis), and to maintain that opening by permanently placing a metal stent within the heart artery. These metal stents help restore normal blood flow to the heart muscle.

Medicated stents are preferred over bare-metal stents by many interventionists because they slash risk of artery re-blockage (restenosis) from about 25% to less than10%.

However, after the study, heart experts say the drug-coated therapy may be too aggressive. The reason behind is that bare metal stents let a thin layer of cells to grow over them to make a biological lining. The medicines in the drug-coated ones prevent tissue growth that could block the arteries from growing. While the excessive tissue growth is bad, a thin layer of cells is necessary to cover the bared metal, which if not covered can cause clotting and block arteries.

Now the drug-coated stents therapy is facing questions from heart experts about the device’s long-term safety. The Safety concerns were raised when a Swiss-Dutch study revealed that the medicated stents carry a higher risk of potentially fatal blood clots than older, bare-metal stents, in rare cases.

After the sensational disclosure of the use of medicated stents, some cardiologists say they will be more cautious about their use in the future. In the United States alone this year, about one million patients will undergo a balloon angioplasty procedure and of them nearly 80 to 85% will receive a stent placement.

The study followed up 8,146 patients for 18 months.

Dr. Gabriel Steg of Hospital Bichat-Claude Bernard in Paris, who is also an author of a Swiss study underlining the risks of coated stents, said on Monday, “It raises the flag of caution over the indiscriminate use of first-generation, drug-eluting stents and reminds us that we should stick with tested indications and not overextend this to any patient.”

Dr. Christoph Kaiser of University Hospital in Basel, Switzerland, an early critic of the value of drug-coated stents, said new evidence from the recent follow-up program suggested that they might be worthwhile in just one of three cases.

Besides this Swiss-Dutch study, the two other Swiss studies also reported that medicated stents had higher risk of thrombosis compared to bare-metal stents that are not coated with medicine.
As per the estimates of the Interventional Council of India, 60% of the 65,000 stents implanted in the country last year were medicated. Nearly sixty lakh patients worldwide have received coated, or drug-eluting, stents since they were introduced in 2000, with about 1.5 lakh patients using them in India since June 2002.

The market of those stents is estimated at more than $5 billion a year. These coated stents cost around three times as much as bare-metal devices.

This is not the first time the medicated stents are facing the criticism, even three years ago the US Food and Drug Administration issued a warning after receiving more than 290 reports of blood clots in patients using Cypher drug coated devices, with more than 60 deaths associated with them.