Prior aspirin use in unstable angina predisposes to higher risk: the aspirin paradox.
BACKGROUND
Aspirin is the most widely prescribed agent used in prevention of coronary thrombosis. Thus, many patients presenting with acute coronary syndromes have a history of aspirin usage.


METHODS
To assess response to medical therapy in patients taking aspirin prior to admission with an acute coronary syndrome, we reviewed outcomes data from the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events (ESSENCE) and Platelet Receptor Inhibition in Ischemic Syndrome Management in Patients Limited by Unstable Signs and Symptoms (PRISM-PLUS) studies.


RESULTS
Patients with acute coronary syndromes who had taken aspirin prior to enrollment were less likely to have non-Q-wave myocardial infarction on admission (ESSENCE: 16.0% vs. 29.2%, p<0.001; PRISM-PLUS: 34.2% vs. 57.7%, p<0.001). However, prior aspirin users were more likely to be failed by standard medical therapy with unfractionated heparin than non-prior aspirin users (ESSENCE: 21.5% vs. 16.5%, p=0.017; PRISM-PLUS: 23.5% vs. 12.1%, p<0.001). Prior aspirin users received greater benefit from both enoxaparin (21.5% vs. 16.8%, p=0.009) and tirofiban with unfractionated heparin (23.5% vs. 16.0%, p=0.007) than from unfractionated heparin alone. Non-prior aspirin users presented with higher rates of non-Q-wave myocardial infarction.


CONCLUSIONS
Prior aspirin users admitted with acute coronary syndromes may have a more benign presentation, but are more likely to be failed by medical therapy with unfractionated heparin and should be considered as a high-risk group. Enoxaparin or the combination of tirofiban and unfractionated heparin are both more effective than unfractionated heparin in this group.
Lancaster
G I
GI
Danbury Hospital Cardiology Department, 24 Hospital Avenue, Danbury, CT 0681. gil.lancaster@danhosp.org
Lancaster
C J
CJ
Radley
D
D
Cohen
M
M
D000368:Aged; D000789:Angina, Unstable / Q000150:complications / Q000188:drug therapy* / Q000517:prevention & control; D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D001241:Aspirin / Q000009:adverse effects* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000188:drug therapy* / Q000517:prevention & control; D012307:Risk Factors; D016019:Survival Analysis; D016896:Treatment Outcome
D000925:Anticoagulants; D001241:Aspirin