Platelet reactivity and its dependence on alpha-adrenergic receptor function in patients with ischaemic heart disease.

We studied 57 patients admitted to hospital with ischaemic heart disease, including nine patients with variant angina, to evaluate platelet reactivity and its dependence on alpha-adrenergic receptor function. The threshold concentration for biphasic platelet aggregation in response to adrenaline and adenosine diphosphate was measured in fresh platelet rich plasma. There were age related alterations in platelet responsiveness to adrenaline. In 27 age matched control subjects platelets showed adrenaline induced aggregation at a concentration higher than 0.1 mumol. The threshold concentrations for adrenaline and adenosine diphosphate were 0.91 mumol and 4.68 mumol. In 16 patients with acute infarction, 14 with old infarction, nine with effort angina, and nine with rest angina, mean values of platelet aggregation threshold for both adrenaline and adenosine diphosphate were not altered significantly when compared with control subjects. In contrast, the values for adrenaline and adenosine diphosphate in nine patients with variant angina were 0.012 mumol and 2.24 mumol and seven of them showed obvious platelet hyperactivity to adrenaline at a concentration lower than 0.1 mumol. The threshold concentration for adrenaline induced aggregation did not correlate with serum cholesterol and triglyceride levels.