Platelet activation during exercise-induced myocardial ischaemia.

Twenty-six normal subjects (aged 18-52) and eighteen patients with ischaemic heart disease (aged 36-67) underwent maximal 12 lead ECG treadmill exercise testing. Coronary angiography was performed on sixteen of the patients. In-vivo platelet activation was assessed by measuring plasma levels of the platelet specific protein beta-thromboglobulin (beta-tg). The mean beta-tg levels pre- and post-exercise in the normal subjects were 47 (SD: 42- 26-85) ng/ml and 48 (29-78) ng/ml respectively, and in the patient group 68 (43-107) ng/ml and 70 (45-109) ng/ml. There was a significant difference between the two groups at rest (p less than 0.05), but there was no change in either following exercise. Post exercise beta-tg levels showed no correlation with the degree of induced ischaemia as judged by ST segment depression and the number of leads involved. Resting beta-tg levels, however, were positively correlated with the presence and extent of angiographically demonstrable coronary disease (r = 0.53, p less than 0.05). We conclude that in vivo platelet activation is present at rest in patients with coronary artery disease, and whilst related to the presence and extent of such disease is unrelated to induced ischaemia.