Cardiac Stents Overview
Types of Heart Stents continued...
In 1986, French researchers implanted the first stent into a human coronary artery. In 1994, the FDA approved the first heart stent for use in the U.S.
First-generation stents were made of bare metal. Although bare-metal stents almost eliminated the risk of the artery collapsing, they only modestly reduced the risk of restenosis. About 25% of all coronary arteries treated with bare-metal stents would close up again, usually within about six months.
So doctors and companies began testing stents which were coated with drugs that interrupted the process of restenosis. These are called drug-eluting stents, which are now approved by the FDA.
In clinical trials, drug-eluting stents dramatically reduced the rate of restenosis to less than 10%. Drug-eluting stents also reduced the need for repeat procedures in patients with diabetes, a condition associated with an increased risk of restenosis.
Despite these benefits, there were concerns that drug-eluting stents were associated with a rare but serious complication: late in-stent thrombosis, in which a blood clot forms inside the stent one or more years after it's implanted. Because this complication can be fatal, it is extremely important that patients with drug-eluting stents take aspirin and an anticlotting drug such as Plavix, Effient (prasugrel), or Ticlid (ticlopidine) as prescribed, and not stop them without their doctor's approval.
Innovations in Heart Stents
Due to concerns such as late in-stent thrombosis, the use of drug-eluting stents started to decline in late 2006. But many cardiologists believed that fears were overblown. They also began to re-examine whether drug-eluting stents were significantly more effective than the older bare-metal stents, especially in patients with blockages that were deemed to have a low risk of restenosis.
In December 2006, the FDA held a public meeting on the issue of late in-stent thrombosis. While concluding that more information was needed, the agency stated that drug-eluting stents, when used as directed, were not associated with an increased risk of heart attack or death. Subsequent research studies confirmed the safety and effectiveness of drug-eluting stents, prompting the continued development of new stent technologies.
In recent years, the usage of drug-eluting stents has steadily increased, and the global market for heart stents is expected to exceed $8 billion by the year 2015.
Many new second- and third-generation stent designs are under development, in clinical trials, or have been approved for use outside the U.S. These include:
- A stent with a covering that delivers an anti-restenosis drug over a period of several months and then essentially becomes a bare-metal stent
- A stent that is absorbed by the body and disappears after it has done its work
- A stent which uses a bio-engineered coating to quickly create a thin, all-natural layer inside the artery
Other technologies under development include platinum-coated stainless steel stents, diamond carbon-coated stents, and gene therapy/antibody-coated stents.