Physicians must better emphasize to patients the importance of continuing dual-antiplatelet therapy after stenting procedures in order to help decrease the risk of stent thrombosis, according to a study published online Dec. 24, 2010, in the American Journal of Cardiology.
“After implantation of coronary stents, non-adherence to dual-antiplatelet therapy is the main predictor of stent thrombosis, myocardial infarction, and death,” the authors wrote. And while the American Heart Association has issued strategies and recommendations to improve this, predictors for the discontinuation of thienopyridines remain unstudied.
To better understand the problems with treatment adherence, Alexandre S. Quadros, MD, PhD, of the Institute of Cardiology of Rio Grande do Sul, University Foundation of Cardiology, Porto Alegre, in Rio Grande do Sul, Brazil, and colleagues enrolled 405 patients who presented to the cath lab for coronary stent implantation between November 2007 and March 2008, and using a risk score assessed patients’ reasons for discontinuing thienopyridines post-surgery.
At hospital discharge, patients who received a bare-metal stent (BMS) were instructed to take thienopyridines for 30 days with aspirin, while those treated with a drug-eluting stent (DES) were instructed to stay on thienopyridines and aspirin for one year. All patients were administered an explanation of the importance of adherence to dual-antiplatelet therapy at discharge.
At 30 days, the researchers distributed Morisky questionnaires to patients to assess whether or not patients adhered to thienopyridine treatment recommendations. Ninety-seven percent of the patient cohort received BMS while 3 percent received DES—17 percent of patients who received a BMS discontinued drug therapy, while no patients who received DES stopped treatment.
The results showed that 66 patients discontinued dual-antiplatelet therapy and 102 patients had adherence problems, but did not discontinue drug use. The median time frame for discontinuation was 10 days and patients who discontinued treatment were more frequently: unmarried, lacked private health insurance and had an income that was two-times less than minimum wage ($256.00 per month).
The main reasons for discontinuing drug therapy were: medication cost (41 patients), not receiving sufficient information about the importance of a dual-antiplatelet regiment (11 patients) and receiving advice from another physician to stop the drug (10 patients). In addition, reasons included allergies, urinary bleeding, hemorrhagic stroke and refusal to take physician advice to continue the treatment.
Patients who discontinued thienopyridines compared to those who continued therapy said that they were not aware of the importance of the treatment (50 percent vs. 26 percent).
Of the 102 patients who had problems with treatment adherence, 15 percent stopped taking medication at least once during the 30-day period but were still classified as having “better adherence” and 11 percent had “serious problems” with adherence and delayed taking thienopyridines several times per week.
“This information could be useful to target strategies to increase compliance in vulnerable subgroups of patients and aid in the decision of whether to use a drug-eluting stent in patients at highest risk for thienopyridine discontinuation,” the researchers wrote.
And while Quadros and colleagues said that there may be some interventions that could help improve adherence problems, patient involvement will be the key to improvement. While technology systems may help, structured reminders and alerts for patients via telephone calls or consultation will be most helpful.
The researchers said the study may have limitations due to the fact that no long-term outcome data are available. However, they noted that the “adherence rates in this time frame are particularly important because clopidogrel (Plavix, Bristol-Myers Squibb/Sanofi-Aventis) discontinuation in the first month after stenting is the most powerful predictor of stent thrombosis.”
While Quadros et al said that no association between clopidogrel discontinuation and outcomes could be made at 30 days due to the low cardiac event rates, they concluded that previous studies have outlined that thienopyridine discontinuation is a front-line predictor of stent thrombosis, which has a 70 percent risk of MI and 40 percent risk of death.