Comparative Effectiveness of Aspirin and Clopidogrel Versus Aspirin in Acute Minor Stroke or Transient Ischemic Attack

Abstract

Background and Purpose- This study aimed to compare the effectiveness of dual antiplatelet therapy with clopidogrel-aspirin to that of aspirin monotherapy in patients with acute minor cerebral ischemia using a prospective, nationwide, multicenter, stroke registry database in South Korea. Methods- CHANCE trial (Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events)-like patients who met eligibility criteria modeled on the CHANCE trial eligibility criteria, including (1) acute minor ischemic stroke defined as National Institutes of Health Stroke Scale score ≤3 or lesion positive transient ischemic attack within 24 hours of onset and (2) noncardioembolic stroke mechanism. Propensity scores using the inverse probability of treatment weighting was used to adjust for baseline imbalances. The primary outcome was the composite of all stroke (ischemic and hemorrhagic), myocardial infarction, and vascular death by 3 months. Results- Among 5590 patients meeting the eligibility criteria, age was 64±13 year and 62.6% were male. Aspirin and combination of clopidogrel-aspirin were administered in 66.1% and 33.9% of patients, respectively. In unadjusted analysis, rates of the 3-month primary vascular event outcome were lower with clopidogrel-aspirin versus aspirin, 9.9% versus 12.2% (hazard ratio, 0.79 [0.67-0.95]). In propensity-weighted Cox proportional hazards regression with robust estimation, clopidogrel-aspirin was associated with a lower risk of the primary vascular event outcome (hazard ratio, 0.76 [0.63-0.92]) and all stroke events (hazard ratio, 0.74 [0.61-0.90]). Among 6 predefined subgroup analyses, 3 showed potential modification of treatment effect, with lesser benefit associated with the absence of prior antiplatelet use (P_interaction=0.01) and younger age (<75 years, P_interaction=0.07), and absence of benefit associated with small vessel occlusion subtype (P_interaction=0.08). Conclusions- Dual antiplatelet therapy with aspirin and clopidogrel was associated with reduced stroke, myocardial infarction, and vascular death in the 3 months following a presenting minor, noncardioembolic ischemic stroke. Benefits may be particularly magnified in patients with a history of prior antiplatelet therapy, older age, and nonsmall vessel disease stroke mechanism.

Keywords: acute minor stroke; aspirin; clopidogrel-aspirin; dual antiplatelets; propensity score; stroke.