Shorter Duration of Antiplatelet Therapy Reduces Clotting Risk in Patients with Drug-Eluting Stents

NEW ORLEANS, LA--Six months of antiplatelet therapy is equivalent to the 12-month regimen that guidelines currently recommend for patients with drug-eluting stents, according to data from the EXCELLENT study presented at ACC.11, the American College of Cardiology's 60th Annual Scientific Session. These results provide the first evidence from a randomized controlled trial in support of a shorter duration of treatment.

Data suggest drug-eluting stents—while outperforming bare metal stents—have a slightly higher risk of late stent thrombosis, with the most important risk factor being stopping dual antiplatelet therapy (DAT) (clopidogrel and aspirin) too soon. However, long durations of dual antiplatelet therapy can increase the risk of bleeding.

“The recommended duration of dual antiplatelet therapy was 3 to 6 months in the early introduction period of drug-eluting stents,” said Hyeon-Cheol Gwon, MD, PhD, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. “Current ACC/American Heart Association guidelines recommend 12 months or longer without solid scientific evidence,” he said in explaining the rationale for the investigation. In addition, prolonged duration of clopidogrel (Plavix) therapy in addition to aspirin may be associated with greater cost and high bleeding risk.

In the EXCELLENT study, 1,443 patients from 19 centers were randomly assigned to 6 or 12 months of DAT following implantation with a stent that released either everolimus or sirolimus. The hypothesis going into the study was that 6 months of therapy is noninferior to 12 months in terms of target vessel failure at 12 months. The 12-month data are available for 1,428 patients; results of the stent trial were previously presented at the Transvascular Cardiovascular Therapeutics conference in 2010. This is the first presentation of findings that compare 6-month and 12-month DAT. Patients will be followed for at least 2 more years.

Patients were included in the study if they had >50% stenosis by visual estimation; evidence of myocardial ischemia (eg, stable angina, unstable angina, recent infarction, silent ischemia), and a positive functional study or reversible changes in the ECG that corresponded with ischemia. The target lesion was to be located in a native coronary artery; there were no limitations on lesion length or multiple stenting.Baseline characteristics were similar between the two groups. Median age was approximately 63 years and >60% of patients were male.

Target vessel failure, defined as cardiac death, myocardial infarction (MI), and target vessel revascularization, occurred in 34 of 716 patients (4.7%) in the 6-month group and 31 of 712 patients (4.4%) in the 12-month group (HR=1.17 [0.73–1.89]). For this primary end point, the 6-month group was noninferior to the 12-month group, with a prespecified noninferiority margin of 40% (P=0.0031). A subgroup analysis found that for patients with diabetes, relative risk favored treatment with 12 months of therapy (HR=3.15) compared with 6 months of therapy in those without diabetes (HR=0.42; P<0.001 for the interaction).

For the safety endpoint—a composite of death, MI, cerebrovascular accident, stent thrombosis, and a type of major bleeding—results were 24 (3.4%) in the 6-month group and 22 (3.1%) in the 12-month group (HR=1.13 [0.64–1.99]). Major adverse cerebrovascular and CV events for these groups were 54 (7.5%) and 60 (8.4%), respectively. A subgroup analysis by stent type showed even numbers by outcome for the everolimus stent at 6 and 12 months, but the study was underpowered to compare the two regimens reliably for death, MI, and stent thrombosis.

“Our results may be very reassuring for many physicians who may need to discontinue clopidogrel before the routinely recommended 12-month duration for various reasons,” Gwon said. “However, we need to remember that this study was underpowered to test the noninferiority of the shorter duration for hard endpoints. A larger-scale randomized controlled trial is needed.”