Evidence for local platelet activation in pulmonary vessels in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease.

To investigate the relationships between local platelet activation in pulmonary vessels and pulmonary artery pressure circulating platelet aggregates and plasma beta-thromboglobulin (beta-TG) levels were evaluated in peripheral venous blood and blood from different sites of pulmonary circulation (right ventricle, pulmonary artery and arteriolo-capillary bed) in 29 patients with COPD. Fifteen had pulmonary hypertension and 14 normal pulmonary artery pressure. In normotensive COPD no significant differences could be found in platelet aggregation and beta-TG levels among different sampling sites. On the contrary in patients with pulmonary hypertension a significant increase of platelet aggregates and beta-TG levels was found in blood withdrawn from the arteriolo-capillary bed. A significant correlation was demonstrated between platelet aggregation and both mean pulmonary artery pressure and pulmonary vascular resistance. These results indicate that in patients with pulmonary hypertension secondary to COPD a local platelet activation in pulmonary vessels does occur and may contribute to the maintainance of elevated pulmonary vascular resistance.