Primary prevention of myocardial infarction: aspirin is not as useful as it seems.

Background: Aspirin has not been reliably shown to reduce all-cause and cardiovascular mortality but can prevent symptomatic myocardial infarction. However, silent myocardial infarction (SMI) is not uncommon in clinical practice. No meta-analysis has compared the effect of aspirin administration on primary prevention of all myocardial infarctions, including SMI.

Methods: We systematically searched PubMed, Embase, Web of Science, Cochrane Library and Google Scholar for randomized double-blind controlled trials evaluating the effect of aspirin on primary prevention of all myocardial infarctions, including SMI.

Results: The current meta-analysis included 9 trials involving 67,486 patients and 67,557 controls on aspirin primary prevention of all myocardial infarctions. When SMI was included in the total number of myocardial infarctions, the aspirin effect on the primary prevention of myocardial infarction was not as significant as expected [risk ratio (RR): 0.883; 95% confidence interval (CI): 0.780 to 1.001; P=0.052].

Conclusions: Aspirin may not provide a primary preventive effect in all myocardial infarction patients. Previously demonstrated reductions in myocardial infarction are not present when SMI is included.