Platelet abnormalities in chronic thromboembolic pulmonary hypertension

The reasons for non-resolving thrombosis in chronic thromboembolic pulmonary hypertension (CTEPH) have not been fully elucidated. Despite platelets being implied in its pathogenesis, they have been poorly studied. We hypothesized that platelets would be altered in CTEPH. The aim of our study was to compare selected platelet parameters in CTEPH patients with healthy subjects. The study included healthy subjects (n = 50) and patients with CTEPH (n = 47). We investigated platelet count, mean platelet volume (MPV), and platelet aggregation-spontaneous (SPA) and induced by various concentrations of five agonists. In addition, some other hemostatic parameters were also investigated to provide a comprehensive view on hemostasis. We found a decreased platelet count [212 (171-251) versus 248 (205-408) 109 L-1, P<0.01], higher MPV [11.3 (10.5-11.7) versus 10.1 fL (9.4-10.4), P<0.001] and higher SPA [9.5 (7.1-12.4) versus 5 (1.3-9) %, P<0.001], but a decrease of induced platelet aggregation (only by maximal agonist concentrations) in CTEPH patients compared to controls. These changes were accompanied by a significant increase of plasma fibrinogen, factor VIII, von Willebrand factor (antigen and activity), and plasminogen activator inhibitor. Thus, we can conclude that CTEPH is accompanied by a prothrombotic state, including platelet abnormalities. They reflect a higher platelet turnover/reactivity and specific platelet behavior (impaired aggregation) in these patients. Our findings imply that platelet disorders can contribute to the pathogenesis of CTEPH. However, further research would be desirable to better understand the reason for this finding.