Metal stents are used to open clogged arteries in heart patients. The main problem with metal stents is that a lot of clotting and scar tissue can form around the stent and cause the artery to close up again. At first, manufacturers tried to make stents out of gold and platinum to reduce the reaction people's bodies would have to the stents, but the clotting and scaring still occurred. Eventually, a stent was produced that could be coated with drugs to prevent clotting and scaring. These stents are called drug-eluting stents, and here is a brief overview of how they work.
The method for inserting a drug-eluting stent is the same as the original metal stent. The stent is slipped onto a tiny deflated balloon at the end of a thin tube. This tube is inserted into an artery and snaked through the artery until it reaches the blockage.
The balloon end is pushed through the blockage and inflated. The blockage is pressed against the artery wall as the balloon inflates, and the stent also opens and is pressed against the artery wall. The stent will keep the blockage pressed against the wall after the balloon is deflated and removed from the artery.
Researchers started to coat the stents with drugs in the late 1990s and early 2000s to prevent a condition called restenosis. Restenosis occurs when the area of the blocked artery that was opened during the placement of the stent gets blocked again – often by clotting and scar tissue. Drugs can be added to the stent to reduce the amount of clotting and scaring.
Sirolimus-based drugs were the first ones used on the stents. Sirolimus is made from bacteria and is a heavy-duty immunosuppressive agent, which lowers the immune response that develops the clots and limits the amount of scar tissue that can develop around a stent.
Stents can also be coated with a substance called paclitaxel. Paclitaxel is made from the bark of the Pacific yew (the Pacific yew is a conifer tree typically found in the Pacific Northwest region of the U.S.) and is normally used to treat certain types of cancers, but its antiproliferative properties which limit cell growth (like scar tissue) is also useful in preventing restenosis in stent patients.
The drugs are coated on the stent and are absorbed into the artery walls over an extended period of time while your body adjusts to the stent. The drugs have helped reduce the rate of restenosis from roughly 25 percent of stent patients using traditional metal stents to under 10 percent today for those using drug-eluting stents. For more information, talk to a cardiology specialist in your area.