Dose-dependent effect of aspirin on carotid atherosclerosis.

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Abstract
Antiplatelet treatment with aspirin is well established as secondary prophylaxis after a transient ischemic attack or minor ischemic stroke, but the effect of aspirin treatment on the course of carotid atherosclerosis is unknown. We investigated the effect of aspirin on the initial stages of carotid atherosclerosis. Patients were recruited from a prospective, randomized, double-blind clinical trial to compare two doses of aspirin (900 mg versus 50 mg daily) with regard to restenoses after lower limb angioplasty. Of the 383 patients admitted to the angioplasty trial, 27 patients with 104 small carotid atheroma (< 50% lumen narrowing) were examined at entry and after 1 year of aspirin treatment with the use of a high-resolution ultrasound duplex system. Disease progression and regression were defined by a change of maximal plaque area (as measured by longitudinal ultrasound sections) of more than 2 SDs of the method. The change in plaque area was significantly different for the treatment groups: Average plaque size remained unchanged after treatment with 900 mg aspirin daily but increased markedly after treatment with 50 mg aspirin daily (p = 0.011). There were significantly more lesions in the 50-mg group showing progression than in the 900-mg group (23 plaques [47%] versus 13 plaques [24%], p = 0.025). Ultrasonic disappearance of a lesion was observed only in the 900-mg group in nine cases (seven soft plaques and two ulcerative plaques, p = 0.018). The six patients on 50 mg aspirin who continued smoking during the study showed significantly more progression compared with the seven nonsmokers in the 50-mg group (17 plaques [59%] versus six plaques [30%], p = 0.038). The results of our study indicate that aspirin treatment slows carotid plaque growth in a dose-dependent fashion, with a dose of 900 mg daily more efficient than 50 mg daily.