To medicate or not to medicate

Drug-eluting stents appear more effective in treating narrowed arteries

Reviewed by Dr. Choo Gim Hooi, Sime Darby Medical Centre, Subang Jaya, Malaysia

The heart is a pump that carries blood to the rest of the body; in turn, the heart also requires oxygen-rich blood to function, carried to it by the coronary arteries. With time a fatty substance called plaque builds up in these arteries, narrowing them and limiting the amount of blood that can flow to the heart. This narrowing of the arteries leads to coronary artery disease (CAD), which killed 7.25 million people around the world in 2008. If the coronary arteries become completely blocked off, a heart attack occurs. A severe blockage that cannot be treated with lifestyle changes or medication often require an angioplasty, where a balloon is expanded in the narrowed artery to widen it. A stent is usually inserted at the same time to keep the artery open.

A stent is a small mesh tube, usually made of metal, which is placed around the deflated balloon used in the angioplasty procedure and inserted through a catheter into the narrowed artery. When the balloon is inflated to push the plaque into the walls of the artery, expanding it, the stent is also stretched into the walls of the artery. When the balloon is deflated, the stent remains in place, holding the artery open. Cells in the artery will eventually grow over the stent, covering it completely so that the treated portion of the artery looks no different from the rest of it.

Unfortunately, in up to one out of five patients (20-30%) who undergo angioplasty with bare metal stenting, restenosis—the re-narrowing of the treated artery—will occur. As the tissue grows over the stent, scar tissue can form and overgrow, creating a new obstruction in the artery. In this case the artery will need to be treated again, with another angioplasty procedure or something more drastic, like bypass surgery.

To combat the high possibility of restenosis, drug-eluting stents, i.e. stents that are impregnated with medicine to reduce the development of scar tissue can be inserted instead. Medicated stents are now commonly used in the United States. The risks associated with drug-eluting stents include inflammation caused by the body reacting to the polymer coating of the stents and an increased risk of thrombosis, the formation of blood clots within the vessel.

Drug eluting stents have been shown to lower rates of restenosis up to 5 years post-implant.

There is however a concern with potential late stent thrombosis especially with the earlier generation of stents. Newer developments in stent technology, for example, with the use of bioabsorbable polymer, improved stent designs appear promising in maintaining the efficacy of drug-eluting stents in preventing restenosis whilst reducing the risk of stent thrombosis.

Sources:

• http://www.uchospitals.edu/specialties/heart/services/surgery/beating-heart.html
• http://abcnews.go.com/Health/HeartFailure/beating-heart-bypass-surgery-riskier/story?id=8999797
• http://en.wikipedia.org/wiki/Off-pump_coronary_artery_bypass
• http://en.wikipedia.org/wiki/Coronary_artery_bypass_surgery

Related articles:

• The silent killer
• Skipping hearts
• To pump or not to pump?
• The fight for his life

• Tip a friend
• Feedback