Patterns of failure of aspirin treatment in symptomatic atherosclerotic carotid artery disease

Abstract

Over a 24-month period, 291 patients were consecutively admitted to the West Haven Veterans Administration Medical Center with new ischemic neurological symptoms. Of these, 90 patients (31%) developed ischemic neurological symptoms while taking aspirin (aspirin treatment failure). Of those in whom aspirin treatment failed, 66 patients had ischemic symptoms in the distribution of the carotid artery. Aspirin treatment failed in 21 patients with severe carotid stenosis (greater than 75% stenosis). Eleven of these 21 patients had cerebral infarctions while taking aspirin, and 7 of these 11 infarcts occurred without the prior warning of transient ischemic attacks. Aspirin treatment failed in 45 patients with lesser degrees of carotid stenosis. Transient ischemic attack without permanent ischemia was the most common manifestation of failure in these patients. Infarction occurred in only 12 of these 45 patients and in only 4 patients did infarction occur without warning. We conclude that patients with symptomatic high-grade carotid stenosis (greater than 75%) in whom aspirin treatment failed are likely to suffer an infarct without warning as the first sign of treatment failure (P less than 0.033). We suggest that this subgroup of patients should be considered for alternative forms of therapy.