Patients with myocardial infarction who stopped taking antiplatelet drugs within 30 days of receiving a drug-coated stent had nine times the risk of death compared to patients who followed doctors' orders.
The study is published in the journal Circulation.
" An alarming one in seven patients in our study stopped taking their antiplatelet medication within the first 30 days of receiving a drug-eluting stent ( DES ), even though they were prescribed the drugs at the time of hospital discharge and recommendations are to continue them for a minimum of three to six months after the procedure," said John A. Spertus, lead author of the study and at the Mid America Heart Institute in Kansas City.
Researchers looked at the real-world use of drug-eluting stent in myocardial infarction patients and a class of drugs called thienopyridines that work along with Aspirin to help keep platelets in the blood from clumping and leading to the formation of blood clots.
Thienopyridines include the drugs Clopidogrel ( Plavix ) and Ticlopidine.
Several studies have confirmed the benefits of drug-eluting stent in preventing restenosis.
However, with stents there is the potential problem of stent thrombosis, which can be associated with devastating consequences.
Antiplatelet agents, including thienopyridines, reduce the likelihood of stent thrombosis.
According to Spertus, no previous studies have defined the frequency and consequences of prematurely discontinuing thienopyridine therapy.
The risk of stent thrombosis with bare-metal stents decreases rapidly after two to four weeks, and patients typically need thienopyridines for only about one month.
In comparison, with drug-eluting stents the risk of stent thrombosis lasts for a longer period of time and patients with DES require prolonged thienopyridine therapy ( typically for several months ).
In a 19-center study of 500 heart attack patients ( average age 61 years and 68 percent male ) who received a drug-eluting stent and were discharged with prescriptions for thienopyridines, 68 patients ( 13.6 percent ) stopped their medication within 30 days.
Those who stopped were:
- less likely to have completed high school;
- less likely to be married;
- more likely to avoid health care due to cost;
- more likely to have pre-existing cardiovascular disease or anemia when they arrived at the hospital; and
- less likely to have received discharge instructions about their medications or be referred for cardiac rehabilitation.
After one year, 7.5 percent of patients who stopped their medication within the first 30 days had died compared to 0.7 percent of the compliant patients.
In addition, 23 percent of those who stopped their medication early were readmitted to the hospital, compared to 14 percent of those who continued their medication, he said.
" The rate of death was significantly higher and the frequency of cardiac hospitalizations was almost twice as great over the next 11 months among those who stopped their thienopyridines as compared to those who continued them," Spertus said.
Researchers said previous studies under controlled conditions found that the combination of drug-eluting stent plus three to six months of antiplatelet medication effectively prevented restenosis for patients with atherosclerosis.
Yet, clinical trials differ from real-world practice where patients may have less intense follow-up or limited access to the medications they need. That's why it was important to see how patients would fare under real-world conditions, including those getting stents on a more emergency basis, such as for treatment of myocardial infacrtion, Spertus said.
" The lack of a high school education was associated with a 79 percent higher risk of stopping treatment," Spertus said. " This finding indicates that more patient education about why the medicine is necessary could save lives.
Treatment decisions made at the height of clinical urgency can have long-lasting consequences on the chronic care that patients need to have the best possible outcomes. In this case, prolonged use of thienopyridines after drug-eluting stent implantation for heart attack treatment is clearly required for patients to get all the benefits of reduced restenosis and to avoid the catastrophic complication of stent clotting, he said.
Source: American Heart Association, 2006