Significance of thromboxane A2 in myocardial ischemia in patients with coronary artery disease.

To examine plasma levels of vasoconstrictive prostanoid (thromboxane A2) in patients with coronary artery disease, amounts of its product, thromboxane B2, in acidic lipid extracts from plasma were determined by a radioimmunoassay. Peripheral venous samples were obtained in 14 normal subjects and 12 patients with coronary artery disease, and simultaneous aortic and coronary sinus blood samples were obtained at rest, during pacing, and after pacing in eight cases who were subjected to atrial pacing stress test. Mean thromboxane B2 levels in peripheral venous blood in 14 normal subjects were found to be 243 +/- 96 pg/ml. Of nine cases with angina pectoris on effort (angiographically documented severe coronary artery stenosis), five exhibited increased thromboxane B2 levels in peripheral plasma. Three cases of a variant form of angina pectoris exhibited pronounced increases in peripheral thromboxane B2 levels. Of eight cases subjected to atrial pacing stress test, three exhibited marked increases in thromboxane B2 levels in coronary sinus effluent at peak pacing, two of which were accompanied by typical anginal pain during the test. These findings suggest that increased thromboxane A2 production may be associated with altered thromboxane metabolism. This may occur because of altered interactions between functions of vascular wall and blood platelets within coronary circulation in patients with coronary artery disease.