Cardiac Stents Overview
Types of Heart Stents continued...
Because no new support is left at the site of the blockage during balloon angioplasty, in a small percentage of cases, the artery will resume its previous shape or even collapse after the balloon is deflated. In addition, about 30% of all coronary arteries treated with balloon angioplasty are affected by restenosis.
To help solve these problems, doctors developed small stents which could be mounted on the balloon section of the catheter and inserted into a blood vessel. During a stenting procedure, the stent expands when the balloon is inflated, locks into place, and forms a permanent scaffold to hold the coronary artery open even after the balloon is deflated and removed.
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 clopidogrel (Plavix), prasugrel (Effient), or ticlopidine (Ticlid) 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.