Your Questions on Heart Stents Including Those on Problems With New Stents Answered

 What is a stent?

A stent is a mesh-like structure that is installed in the artery after balloon inflation opens it. It acts as a retainer wall and prevents the artery from collapsing.

What is the difference between ‘new’ and ‘old’ stent?

First the names: the old stent is called bare metal stent and the new one is called drug-coated or drug-eluting stent. The old stents are simply made of metal. The new stents have a polymer coating on them. This polymer coating is impregnated with a drug that is released slowly over time.

Why was there a need for a drug-eluting stent?

Stents are a great improvement over simple balloon angioplasty. However, about one out of every five stents (20%) closes up after placement in the heart artery. It is called stent stenosis. This is mostly due to scar formation. The new drug-coated stents came to the market with a premise that the chances of stent stenosis will be negligible. The post-marketing studies have shown stenosis rate for the new stents to be up to about 10%; still an improvement over old stents.

I am hearing a lot about problems with new stents. What exactly is wrong with new stents?

Once bare-metal stents are installed, they are covered by the person’s own smooth endothelium within a few weeks. This leads to a smooth surface-somewhat like a plaster coat on a rough wall. The new drug-eluting stents however have polymer coating that prevents the smooth endothelium from covering its surface. This leaves a rough surface exposed to the blood flow inside the artery, which leaves it prone to a blood clot (thrombus) formation. This problem is called late stent thrombosis. The blood clot formation can lead to heart attack and possible death. This potentially fatal problem is unique to drug-eluting stents.

If new stents can cause fatal problems, why not take them off the market?

The new stents came to the market with the premise of solving a problem that has plagued the old stents: stent stenosis. This problem can lead to repeat procedures to open plugged up arteries in some cases. The chance of new stents stenosing or closing again is less than that for the old stents. The late stent thrombosis is reportedly a rare occurrence.

What about a moratorium on the new stents till the problem is better studied?

The experts still think that benefits of new stents outweigh their potential risks. From the manufacturer stand point, moratorium tends to be a fatal public relations event in most of the cases. Remember saccharin: the artificial sweetener that got put under moratorium in 1977? I do not think many of us know that moratorium was withdrawn in 1991 and that in 2000, the U.S. Congress repealed the law requiring saccharin products to carry health warning labels.

Does that mean that public safety does not matter? Are we going to let all those people die from this complication?

A lot is being done to determine the enormity of the problem of late stent thrombosis and to decrease the chances of late stent thrombosis. The new stents could mean potential death knell for stent stenosis. Research trials showed these stents to be beneficial in blockages of certain diameter and length. Our desire to get rid of frustrating problem of stent stenosis lead to several off-label uses of new stents. The suggestion for now is that we should refrain from off-lable use.

A prolonged use of blood thinners Plavix and aspirin is being suggested after placement of new stents. It is said that we may be able to take care of the problem of late stent thrombosis by using Plavix and aspirin for at least a year after stent placement. Some authorities are suggesting that we should continue to use Plavix and aspirin till we have studied the phenomenon of late stent thrombosis better.

What are your thoughts?

1. We should refrain from off-label use of new stents for now. This should be done while we continue to study the phenomenon of late stent thrombosis in all the patients that got new stents.
2. We should continue to use Plavix and aspirin in patients who get new stents till more information is available. This should be done while understanding that these recommendations are for the most part empirical.
3. The question that needs to be answered is: is Plavix and aspirin use really going to take care of the problem of late stent thrombosis? If yes, how long do patients need to be on Plavix and aspirin? Both these questions need to be answered through well-designed trials.
4. For the sake of my patients, new stents will be unattractive if  life-long Plavix and aspirin are recommended after their deployment. What if you have to be off blood thinners for some reason like bleeding ulcer or brain hemorrhage- say ten years down the line?

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