Thromboxane Generation and Platelet Aggregation in Survivals of Myocardial Infarction

Summary

Arachidonic acid (AA)-induced platelet aggregation was studied in platelet-rich plasma of 30 male patients who survived myocardial infarction and in 30 healthy men of similar age. Mean platelet aggregation thresholds to A A were 746 ± 62 μM, and 869 ± 57 μM, respectively. Only in 2 healthy subjects, but in 12 patients, irreversible platelet aggregation was induced consistently with low concentrations of AA, under 500 μM. The rate of conversion of AA to thromboxane A₂ (TXA₂) by platelets of these patients was augmented. Furthermore, less endogenous TXA₂ was required to trigger aggregation of their platelets as compared to the controls. We have also shown that in platelet-poor plasma of these patients with “hyperreactive” platelets there exists a transferable factor which makes platelets of healthy subjects more prone to aggregatory action of AA.

It is proposed that the assessment of platelet aggregability with AA provides a tool for identifying a subgroup of patients with coronary heart disease who might substantially benefit from the secondary preventive treatment with aspirin and with other antiplatelet drugs which inhibit the generation of TXA₂ in platelets.

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