Platelet activation during exercise-induced myocardial ischemia.

Because platelet activation may be important in the worsening of coronary atherosclerosis, we used a radioimmunoassay for platelet factor 4 to study platelet behavior in patients with coronary-artery disease. Forty patients had paired blood samples withdrawn for measurement of the plasma level of platelet factor 4 before and after a standardized exercise-tolerance test. Twenty patients had positive tests, and 19 of those 20 had clinical or angiographic evidence of coronary-artery disease. Eleven of the 20 had a greater than 50 per cent increase in platelet factor 4 after exercise. The remaining nine had positive exercise tests without rises in platelet factor 4. Elevated levels returned to normal within 15 minutes of exercise. Eighteen of 20 patients with negative exercise tests had no rise in platelet factor 4 after exercise. We conclude that a subset of patients with coronary-artery disease and exercise-induced myocardial ischemia had evidence of platelet activation and secretion. (N Engl J Med 302:193-197, 1980).