U nstable angina is a syndrome in which the occlusion of coronary arteries by plateletdependent thrombus formation may result in myocardial infarction and death.' Angiographic2 and angioscopic3 evidence of thrombus formation is complemented by the measurement of increased concentrations of thromboxane (TX) metabolites in plasma and urine during ischemic episodes in patients with this disease.4 ...