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Late blood clots tarnish drug-coated stents.

Article Excerpt
Uncommon complication raises questions about who really needs a drug-coated stent and how long to continue drug therapy after getting one.

Medicine is both science and art. It's also a balancing act, teetering between the benefits of therapies for treating and preventing illness and their hazards. When it comes to new drugs, devices, and operations, healing powers are usually seen first, with harms trickling in over time. That's been the case for drug-coated stents. They were hailed as a huge innovation when introduced in 2003 and almost universally adopted for holding open cleared coronary arteries. Now, with more than four million drug-coated stents implanted in the U.S. alone, an uncommon but hazardous side effect known as late stent thrombosis is giving some cardiologists pause about using them.

How stents help

Stents are flexible wire-mesh cages slightly smaller than the spring inside a ballpoint pen. The early ones were made of bare metal. They are placed inside an artery immediately after balloon angioplasty has cleared it of cholesterol-filled plaque. Cells lining the artery underneath the stent gradually grow over and around the metal struts, embedding the stent in place and covering it with healthy living tissue.

About one-third of the time, though, the healing response goes overboard. The cell growth doesn't stop once the stent struts are covered, but continues into the open space in the middle of the stent. This overgrowth, called restenosis, narrows the space available for blood flow, sometimes even more than the initial blockage, and leads to the...