Resistance to aspirin: Prevalence, mechanisms of action and association with thromboembolic events. A narrative review

Abstract

Objectives

The purpose of this study is to review the prevalence of aspirin resistance in patients with a high risk of cardiovascular events, and secondly, to investigate its epidemiology and mechanism of action, and the clinical consequences it can provoke.

Material and methods

A search was run on PubMed, EMBASE and Reviews Database for English or Spanish articles on aspirin resistance published up to November 2008. Additional studies were obtained by searching the reference lists in the selected articles for articles relevant to our secondary objectives.

Results

Aspirin resistance is described as affecting 0% to 57% of the population, and is related to a decreased protective effect against strokes and cardiovascular events. Many modifiable and unmodifiable factors can affect the efficacy of antiplatelet drugs. Possible strategies for overcoming this decreased antiaggregant effect include increasing the aspirin dosage or dual therapy with another antiplatelet agent.

Conclusions

Lack of response to aspirin decreases its protective effects. However, lack of a standard definition for aspirin resistance, the absence of diagnostic reference methods to identify resistant patients, and the different mechanisms of action involved in platelet aggregation call the clinical importance of this fact into question. Additional well-designed studies are needed to detect patients with real resistance in order to have more effective prevention of cardiovascular morbidity and mortality.