Previous studies indicate that patients with cardiovascular disease have a variable response to aspirin. Despite treatment with aspirin a large number of patients suffer a myocardial infarction. This has given rise to the phenomenon "aspirin low-responsiveness". Laboratory aspirin low-responsiveness can be defined as the failure of aspirin to inhibit platelet production of thromboxane A2 or inhibit thromboxane-dependent platelet aggregation. Whether a low platelet response to aspirin results in an increased risk of future thrombotic events is of great clinical significance, but is still unknown.