Aspirin prevents or delays atherogenesis and subsequent arterial occlusions. Patients who are relatively resistant to aspirin have a higher rate of vascular occlusive events. We evaluated the hypothesis that in patients with a previous myocardial infarction (MI) relative resistance to aspirin was related to risk factors for coronary heart disease (CHD). We studied 192 patients with a history of at least 1 MI including 136 males and 64 females. Mean age was 62. Compliance was assured by studying patients 2 hours after they were observed to ingest 325mg aspirin and confirmed with a qualitative assay (arachidonic acid 1.0mM stimulated light aggregometry) that detected aspirin inhibition of platelet aggregation in all of the study patients. To assess amount of aspirin inhibition of platelet aggregation (aspirin resistance) platelet prostaglandin agonist (PPA) 30mM stimulated light aggregation was performed (

Schwartz
J. Lab Clin Med
2002
;
139
:
227
). A CHD risk assessment score that includes diabetes, HDL, total cholesterol, high blood pressure (HBP) smoking and age was used as a measure of 10 year risk for CHD. Statistical comparisons were evaluated using a univariate general linear model. A significant relationship was observed between platelet resistance to aspirin inhibition and increased CHD risk (p=0.03). Evaluation of individual CHD risk factors showed that diabetic patients were more resistant to aspirin as demonstrated by an increased slope of aggregation (p=0.02) a decreased time to 50% aggregation (p=0.04) and a linear relationship between an increase in fasting blood sugar and an increased aggregation slope (p=0.05). A higher (BMI) (p=0.05) or a lower HDL (p=0.02) were also related to aspirin resistance. Although decreased aspirin inhibition of platelets was observed in patients who smoked or had HBP, these differences were not significant. We conclude that in patients with CHD a relative resistance to aspirin inhibition of platelet aggregation correlates with a commonly used risk assessment equation and with the presence of diabetes, increasing BMI or decreasing HDL. This suggests the hypothesis that CHD patients who have a higher risk for CHD, or those who have diabetes or obesity or a decreased HDL, may benefit from additional platelet inhibiting medications.

Topics:
agonists, arachidonic acid, aspirin, aspirin resistance, atherogenesis, coronary heart disease risk, diabetes mellitus, fasting blood glucose measurement, high density lipoprotein decreased, high density lipoproteins

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2005, The American Society of Hematology
2004
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