Aspirin resistance: an update.

Aspirin resistance (AR) still lacks a universally accepted definition, but it may be discussed as either a laboratory phenomenon or a clinical presentation. Laboratory resistance is mainly defined as abnormal platelet response to aspirin, whereas the clinical manifestation is the failure of aspirin to prevent cardiovascular events. Although there is evidence of an association, it appears that a laboratory abnormality in platelet function is not the only risk factor for the clinical manifestation of AR. Therapies for primary and secondary prevention of AR still need to be elucidated, but there are some data to suggest that in an acute episode of aspirin failure because of AR, different therapeutic interventions need to be considered.