Introduction and Hypothesis: Approximately a third of stroke/TIA events occur in patients taking daily Aspirin. We studied the comparative effectiveness of FDA approved antiplatelet agents (Aspirin, Clopidogrel, and Aspirin-dipyridamole or ASA+DP) in prevention of recurrent vascular events in stroke/TIA patients on Aspirin.
Methods: Consecutive patients identified as having stroke or TIA were screened and enrolled into this prospective longitudinal registry. Patients on dual antiplatelet therapy or oral anticoagulants were excluded. Patient’s etiological stroke subtype, medication history, medication compliance and Aspirin Platelet Function Test were assessed at baseline. Changes in antiplatelet regimen including Aspirin dose, Clopidogrel, ASA+DP, changes in statin therapy were recorded. Follow up 6 and 12 month phone visits were conducted to assess primary outcomes (stroke/TIA, MI, death), adjudicated by chart review.
Results: A total of 183 subjects (mean age 68+12, 58% males, 50% white, 44% African-American) were enrolled over a 24 month period on Aspirin. Majority (63%) had ischemic stroke (NIHSS: 0-21) and remaining (37%) had TIA (ABCD2: 2-7). Ischemic strokes were attributed to penetrating artery disease (41%), large artery atherosclerosis (35%), other/undetermined (18%), and cardiogenic (6%). After 12-months, 4.9% of participants on Clopidogrel, 15.1% of participants on aspirin and 35.3% of participants on ASA+DP had a primary outcome (p=0.006), depicted in the Kaplan-Meier curve. Changes in Aspirin dose from 81mg to 325mg or statin therapy regimen did not appear to impact primary outcome.
Conclusions: This study shows a significant difference in secondary vascular event within 12 months of stroke/TIA on Aspirin, with effectiveness recorded in the order: Clopidogrel>Aspirin>ASA+DP. A larger randomized pragmatic trial may help ascertain this finding and clarify if specific subtype benefit from specific antiplatelet agent.