Increased fraction of circulating activated platelets in acute and previous cerebrovascular ischemia.

Determination of circulating activated platelets may be helpful to estimate the prognosis and to stratify therapies in arterial vascular disorders including stroke. We used flow cytometry and phase contrast microscopy to study whether the fraction of platelets expressing p-selectin and CD63 and the fraction of platelets with shape change are increased in patients with acute and previous cerebrovascular ischemia. The proportion of platelets expressing activation dependent antigens was higher in patients with acute (n = 24; p-selectin: 8.23 +/- 4.21%; CD63: 3.53 +/- 2.53%) and with previous cerebrovascular ischemia (n = 46; 3.86 +/- 1.98%; 2.80 +/- 1.79%) as compared to age- and sex-matched control subjects (n = 35; 2.17 +/- 0.96%; 1.79 +/- 0.75%; p < or = 0.005, respectively). In patients with previous ischemia, there was no difference between treatment with aspirin (n = 25) or phenprocoumon (n = 21). Hypertension, diabetes mellitus and smoking were not associated with increased antigen expression (analysis of variance). The fraction of discoid platelets and platelet counts were not significantly different between groups. Our results indicate increased expression of platelet neoantigens in acute and to a less degree in previous cerebrovascular ischemia. Ongoing platelet activation after cerebrovascular ischemia despite therapy with aspirin or phenprocoumon indicates that new anti-platelet drugs may be of benefit for these patients. Flow cytometry appears to be a useful tool to assess platelet function in cerebrovascular ischemia.