Clopidogrel Resistance after Minor Ischemic Stroke or Transient Ischemic Attack is Associated with Radiological...

The objective of this study was to compare nonresponders (NR) and responders (R) to clopidogrel with respect to presence of microvascular and macrovascular pathology in a cohort of patients with recent minor ischemic stroke (IS) or transient ischemic attack (TIA).

Seventy-two patients treated with clopidogrel after IS or TIA were evaluated 1 month after onset. Platelet aggregation was measured by multiple electrode aggregometry (Multiplate). Nonresponse was defined according to recent consensus. The degree of cerebral small-vessel disease (cSVD) was evaluated on computed tomography scans of the brain using Fazekas scale for white matter changes. Carotid atherosclerosis was evaluated by ultrasound or computed tomography/magnetic resonance angiography.

Twenty-two percent of patients were NR. Moderate to extensive cSVD was more common for NR than R, 56% versus 25%, odds ratio 3.9 (1.2-12), P = .03. Correspondingly, 39% of patients with cSVD were NR versus 14% of patients with no or mild cSVD. No differences were found between NR and R in prevalence or severity of carotid atherosclerosis. NR had higher platelet aggregation response than R after stimulation with arachidonic acid or thrombin receptor-activating peptide, indicating a general platelet hyperreactivity. In a univariate analysis, hypertension, previous IS, glucose intolerance, pulse pressure above median, and presence of moderate to extensive cSVD were associated with the NR phenotype.

Nonresponsiveness to clopidogrel after minor IS or TIA is associated with radiological cSVD but not with carotid atherosclerosis.

Measurement of platelet function is warranted in patients with cSVD. Larger studies on alternative or tailored antiplatelet treatment for these patients should be initiated.