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Patients who receive drug-eluting stents should continue antiplatelet medications

January 17, 2007

American Heart Association Joint Science Advisory

Patients who have had drug-eluting stents inserted to prop open blocked coronary arteries should continue to take medications to reduce the risk of blood clots for at least one year after the stent is inserted, a new scientific advisory recommends.

The American Heart Association, American College of Cardiology, Society for Cardiovascular Angiography and Interventions, American College of Surgeons and American Dental Association issued the joint advisory today. It will be published in Circulation: Journal of the American Heart Association, Journal of the American College of Cardiology and Catheterization and Cardiovascular Interventions (CCI): Journal of the Society for Cardiovascular Angiography and Interventions.

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, helping to hold it open, which improves blood flow to the heart muscle and relieves chest pain. Drug-eluting stents are coated with medication which is slowly released to reduce the risk of restenosis, or re-blocking of the artery.

The medications clopidogrel and ticlopidine are in a class of prescription drugs called thienopyridines. Thienopyridines and aspirin are known as antiplatelet agents. They are begun before stent insertion to reduce the chance of clotting within the stent, which may result in heart attack or death.

"Despite this benefit, antiplatelet therapy is sometimes prematurely discontinued within the first year after stent implantation," the advisory warns.

This practice is potentially deadly. Stopping antiplatelet therapy too early after a stent is placed is the leading independent predictor of stent thrombosis - blood clots that frequently lead to heart attack and/or death. "Death rates due to presumed or documented stent thrombosis range from 20 percent to 45 percent," the advisory reports.

"We want to alert patients and healthcare professionals that this is a serious medical issue; they shouldn't even think about stopping antiplatelet therapy because it could result in heart attack or death," said Cindy Grines, M.D., chair of the advisory writing committee and a cardiologist at William Beaumont Hospital in Royal Oak, Mich. "If a physician, dentist or surgeon feels that stopping these medicines is absolutely necessary, the patient's cardiologist should be consulted, and the medications should be re-started as soon as possible. Patients are advised to postpone elective procedures if the physician or dentist doing it isn't comfortable with continuing antiplatelet medicine."

Grines noted the importance of taking both medications - aspirin plus the prescription thienopyridine - for what is called dual antiplatelet therapy, which is shown to be most effective for preventing stent thrombosis, or clotting. She said this is particularly true for patients receiving drug-eluting stents, with the risk of thrombosis remaining high for at least one year after receiving a drug-coated stent, as compared with one-to-three months for bare metal stents.

"Drug-eluting stents are both good and bad," Grines said. "They're good because they prevent the tissue growth that causes arteries to re-narrow (restenosis); therefore, a person will be less likely to need repeat angioplasty or bypass surgery. The bad is that the reduced tissue growth means the stent is exposed to the blood for a longer time, which increases the risk of clotting."

Research cited in the advisory showed stent thrombosis in up to 29 percent of patients who discontinued antiplatelet therapy early. In a study of 500 patients who received drug-eluting stents after a heart attack, the death rate over the next 11 months was 7.5 percent for those who stopped taking their prescription thienopyridine medication, compared to 0.7 percent in those who had not stopped therapy. Another study of 652 patients with drug-eluting stents found that discontinuing clopidogrel was associated with a 30-fold greater risk of stent thrombosis.

"Patients should receive appropriate antiplatelet therapy according to existing practice guidelines wherever possible," said Raymond J. Gibbons, M.D., American Heart Association president. "This will usually require patients taking both aspirin and a thienopyridine (most commonly clopidogrel) for periods of up to at least one year after stenting and aspirin indefinitely. Patients should not discontinue either aspirin or the thienopyridine within the first year without consulting their treating cardiologist."

Factors that lead to stopping thienopyridine medications early include drug cost (about $4/day for clopidogrel), physician or dentist instructions to patients to stop taking them before procedures, and inadequate patient education and patient understanding of the importance of taking the medicines. The advisory group made the following recommendations to eliminate early discontinuation of dual antiplatelet therapy:

1. Before implanting a stent, the physician should discuss the need for antiplatelet therapy with the patient. In patients not expected to comply with 12 months of thienopyridine therapy, for whatever reasons, a bare metal stent should be strongly considered.

2. In patients who are likely to require surgery within 12 months of receiving a stent, a bare metal stent or balloon angioplasty with a provisional stent should be considered instead of routinely using a drug-eluting stent.

3. Healthcare professionals must make a greater effort to educate patients before hospital discharge about the reasons for prescribing thienopyridines and for taking the dual antiplatelet therapy, as well as the risks for stopping it early.

4. Patients should be specifically instructed before hospital discharge to contact their cardiologist before stopping any antiplatelet therapy, even if instructed to do so by another healthcare provider.

5. Healthcare providers who perform invasive or surgical procedures should be made aware of the potentially catastrophic risks of prematurely stopping thienopyridine therapy, and should contact the patient's cardiologist to discuss optimal patient management.

6. Elective procedures that carry a risk of bleeding should be delayed until a month after the patient has completed an appropriate course of thienopyridine therapy, which is ideally 12 months after receiving a drug-eluting stent in patients who are not at high risk of bleeding, and at least one month after a bare metal stent.

7. For patients who receive a drug-eluting stent and who must have procedures that mandate stopping thienopyridine therapy, aspirin should be continued if at all possible, and the thienopyridine restarted as soon as possible after the procedure (due to concerns about late stent thrombosis).

8. The healthcare industry, insurers, congress and pharmaceutical industry should insure that issues such as drug cost do not cause patients to prematurely discontinue thienopyridine therapy and incur catastrophic cardiovascular complications.

American Heart Association