Platelet Release Reaction in vivo in Patients with Ischemic Heart Disease (IHD) After Exercise and its Prevention with Dipyridamole

Although an interaction between platelets and arteriosclerotic vessel wall is thought to be important in thrombus formation, a little information was obtained in clinical subjects. We have reported that platelet aggregation Increased in patients with IHD after exercise. To analyse the mechanism of this phenomenon, changes in platelet sensitivity to ADP aggregation, plasma von Willebrand factor and beta-thromboglobulin level were measured in 30 IHD and 30 healthy controls before and Immediately after an isometric exercise (handgrip of 50% voluntary contraction for 2 min). Platelet sensitivity and vWF were determined by original methods detecting microscopically the highest dilution of serially two-fold diluted ADP or test plasma mixed with ristocetin to give platelet aggregation. Beta-TG was measured by RIA Kit. An effect of anti-platelet drug was also observed in IHD. The patients with IHD were administered with placebo or dipyridamole (400 mg/day for 4 weeks) in a crossover single blind fashion. Under placebo, platelet sensitivity to aggregation, vWF and beta-TG increased immediately after the exercise with a statistical significance in IHD. In the healthy control and IHD under dipyridamole, these increases were not observed. The phenomenon may suggest that platelets circulating in sclerotic vessels tend to release and are enhanced in reactivity with smaller stimuli than those in healthy. Such changes might be prevented with dipyridamole.