CIRCULATING PLATELET AGGREGATES INDICATIVE OF IN-VIVO PLATELET ACTIVATION IN PULMONARY-HYPERTENSION

The authors investigated the existence of circulating cellular aggrega tes in 12 patients with moderate to severe pulmonary hypertension, usi ng scanning electron microscopy. Peripheral venous blood was collected in the presence of 11.5 mM buffered ethylenediaminetetraacetic acid, in order to disperse freshly formed disaggregable aggregates. Irrevers ible aggregates represented by platelet clusters and/or platelet attac hment to either leukocytes or red cells were identified in 7 patients with pulmonary hypertension. Endogenous platelet activation was furthe r confirmed by a significant increase in plasma levels of beta-thrombo globulin in comparison with controls (33.8 +/- 14.1 vs 22.7 +/- 11.5 n g/mL respectively, p < 0.025). The presence of irreversible aggregates in the blood stream strongly suggests that cell-cell interactions act ually occur in vivo in these patients. If so, therapeutic measures aim ed at preventing in situ thrombosis and its consequences may be benefi cial in this disorder.