Overview

Drug eluting stents are now widely used to treat blockages of the coronary arteries. These devices generally have drug eluting surfaces (known as Drug Eluting Stents or DESs) to minimise the risk of various after-effects of the stent and the insertion procedure, i.e. restenosis, late stent thrombosis, etc.

The concept of the stent grew out of cardiologists' experience with angioplasty balloons after their invention in the 70s & 80s. Sometimes the wall of the coronary artery became weakened after balloon dilatation - used to press the occluding plaque against the inner wall of the artery thus opening the artery up to increased blood flow.

Although the artery would be opened successfully using a balloon, in a small percentage of cases, the artery would collapse after the balloon was deflated. Sometimes this might not happen until the patient had been moved to the recovery room. Since there was no "fix" available, the only option for this patient was emergency bypass surgery to repair the problem. The solution was the stent, invented in 1986, a metal tube or "scaffold" that was inserted after balloon angioplasty. The stent was mounted on a balloon and could be opened once inside the coronary artery.


While stents virtually eliminated many of the complications of abrupt artery closure, restenosis persisted, i.e. re-blocking of the artery (typically after six-months) was still a problem in about 25% of cases. This necessitated a repeat procedure. The cardiology community also discovered that restenosis, rather than being a recurrence of coronary artery disease, was actually the body's response to the "controlled injury" of the artery by the angioplasty procedure and that the blockage due to restenosis as actually growth of smooth muscle cells, similar to a scar forming over an injury.


Physicians and companies began testing a variety of drugs that were known to interrupt the biological processes that caused restenosis. Stents were coated with these drugs, imbedded in a thin polymer layer for a controlled time-release of the drug. This was the birth of the Drug Eluting Stent (DES). Data shows that, the drug-eluting stent has been extremely successful in reducing restenosis from the 20-30% range to single digits.


The Use of Drug Eluting Coronary Stents :-

A coronary stent is a wire mesh tube used to prop open a previously blocked artery to the heart. The stent stays in the artery permanently, helps hold it open, improves blood flow to the heart muscle and relieves symptoms of chest pains. The artery with a stent, however, can gradually become blocked again. This process, called restenosis, often requires another procedure.

There are two separate issues regarding the safety of drug-eluting stents which should be distinguished by patients and physicians :

The First Issue :-

is well-established from a scientific standpoint. Patients who have had a stent procedure should take both aspirin and another drug that acts against platelets (most often clopidogrel) for periods of one to 12 months, depending on their particular circumstances and the type of stent. Existing joint clinical guidelines from the American Heart Association, American College of Cardiology and Society for Coronary Angiography Intervention include specific recommendations about this. Research published earlier this year has shown that many patients are not following appropriate anti-platelet therapy during the first year after their stenting, and that they are more likely to have heart attacks and die. It is very important that patients do not discontinue their anti-platelet therapy within the first year after stenting without consulting their treating cardiologist.

The Second Issue :-

is less well-established at this time. The suggestion has been made that blood clots within drug-eluting stents are more common at a later date (more than a year after stent placement) than with bare metal stents. There is conflicting data regarding the magnitude and significance of this difference. Some of the patients in these longer-term studies were no longer taking aspirin, which is usually indicated on a lifelong basis for all patients with known coronary artery disease.

Additional studies will probably be required to define the risk of late blood clots in patients with drug-eluting stents and the appropriate therapy to prevent them. In the meantime, it is important that all patients who have undergone stenting procedures continue aspirin indefinitely. Additional therapy should be left to clinical judgment based on individual patient circumstances.


Are Drug-Eluting Stents safe or not ?

Based on all presently available information, drug-eluting stents are safe and effective in most circumstances. The key is you must be willing to take your medications in the prescribed manner and for the prescribed duration to help ensure safety.


It's worth remembering that you basically have four options if your arteries become narrowed, each with risks : -

Bare-metal stents : -

These stents can work well, but have a much higher rate of restenosis than drug-eluting stents. If you will need some type of noncardiac surgery soon (for example, a stomach or hernia operation), you may do better with a bare-metal stent.

Drug-eluting stents : -

As we've been discussing, these stents work well and have a lower rate of restenosis than bare-metal stents. The issue we're trying to sort out is whether the use of drug-eluting stents in some people causes a higher risk of dangerous blood clots. As of right now, we can't give a definitive answer.

Coronary bypass surgery : -

Bypass surgery is used to divert blood around blocked arteries in the heart. This surgery uses a healthy blood vessel harvested from your leg, arm, chest or abdomen and connects it to the other arteries in your heart so that blood is bypassed around the diseased or blocked area. While bypass surgery does work well, it's also more invasive than using stents, which means a longer recovery time. In addition, the risk of complications for bypass surgery can be higher than with stents.

Medications and lifestyle changes : -

This is a good option for many people. If you have symptoms from your narrowed arteries, such as angina, and your condition isn't severe or immediately life-threatening, it may be worth first trying medications such as statins and lifestyle changes such as eating a more balanced diet. This option can be as effective as receiving a stent, especially for those who don't have unstable and "acute" chest pain (angina). Keep in mind that even if you receive a stent, your doctor will likely also prescribe medications such as statins.


What should you do if you have a drug-eluting stent ?

Here's what to do if you have a stent of any kind : -

Take aspirin : -

If you have a stent, you'll have to take aspirin daily and indefinitely to reduce the risk of clotting.

Take anti-clotting medication : -

People with stents are given prescription anti-clotting medications such as clopidogrel (Plavix). The American Heart Association and FDA recommend that people who have had drug-eluting stents inserted should continue to take medications such as Plavix to reduce the risk of blood clots for at least one year after the stent is inserted.

Listen to your cardiologist : -

Always talk with your cardiologist about how long you should take anti-clotting and other medications because the answer will vary depending on the nature of the blockage you had and your risk of bleeding. The most important thing to remember is to take all your medications exactly as your doctor prescribes.

What are my chances of clotting my drug-eluting stent and having a heart attack if I do or do not take Plavix (clopidogrel) and aspirin ?

One study from Duke University evaluated the records of patients who received stents at Duke. People who did not have trouble for the first 6 months had only a 1 in 40 chance of clotting over the next year if they continued their anticlotting medicines, but a 1 in 20 chance of clotting if they stopped their anticlotting medicines 6 months after their stents were inserted. (A)


A different study from Denver evaluated patients beginning one month after stent placement until the end of the first year. They found that 99 patients out of 100 who continued medication were alive at that time. The patients who stopped the anticlotting medicines after only a month and may have discontinued their other medicines as well were older and sicker than the ones who continued the medicines. They had a 1 in 13 chance of dying by the end of the first year. (B)

Another study found that 7 of 121 people (6%) with drug-eluting stents who stopped their medicine developed clots in their stents, while only 4 of many (1790) patients who continued their anticlotting medicine had their stents clot during the period up to 1 ½ years after the stent was inserted. (C)

In a European study, late stent clotting (after 30 days) occurred in 6 per thousand patients per year during the three years after the stent was inserted. (D) One can conclude that it is much better to keep taking the medicine to prevent the stent from clotting than to stop taking the medicine too soon.


If bleeding occurs, how soon do the effects of anticlotting drugs wear off? What can be done to control the bleeding ?

Both aspirin and Plavix (clopidogrel) interfere with the action of existing platelets—the blood cells responsible for controlling bleeding. A study of patients having coronary artery surgery analyzed the frequency of major bleeding in patients in terms of how long before surgery they stopped their anti-platelet therapy (anticlotting drugs). The investigations found major bleeding in 44 patients per 1000 who stopped the medicine 5 days or more before surgery.

The risk increased to 93 per 1000 in those who stopped 3 days before surgery and to 111 per 1000 in those who stopped the day before surgery. If bleeding needs to be stopped immediately, platelet transfusions are recommended.


What is my risk of bleeding while I am on aspirin with Plavix (clopidogrel) ?

In one study of 3759 patients taking these drugs together for 18 months, life threatening bleeding occurred in 3 patients out of 100. A comparison group took aspirin alone and they had a risk of life threatening bleeding in 1 patient per 100. In another study, during an average period of 28 months following stent insertion, patients on aspirin with clopidogrel had a 1.7% chance of severe bleeding and a 2.1% chance of moderate bleeding. In comparison, people receiving low dose aspirin alone had risks of 1.3% for severe bleeding and 1.3% for moderate bleeding.

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