Platelet Reactivity and Treatment With Prostacyclin Analogues in Pulmonary Arterial Hypertension

Background: Prostacyclin analogues (epoprostenol, treprostinil and iloprost) induce vasodilation in advanced pulmonary arterial hypertension (PAH) but also inhibit platelets, increasing patients' bleeding risk. The antiplatelet effects of different prostacyclin analogues have never been compared head-to-head. The goal of the PAPAYA (Platelet Reactivity and Treatment With Prostacyclin Analogues in Pulmonary Arterial Hypertension) trial is(i) to compare platelet function (platelet reactivity, extracellular vesicles concentration and thrombus formation) in patients with PAH treated with prostacyclin analogues on top of endothelin receptor antagonists (ERA) and/or phosphodiesterase type 5 inhibitors (PDE5i) and patients treated only with ERA and PDE5i, and (ii) to compare the antiplatelet effect of different prostacyclin analogues.

Venous blood will be collected from patients treated with prostacyclin analogues (study group; n=40) and patients treated with ERA or PDE5i (control group; n=40). Platelet reactivity will be analysed in whole blood by impedance aggregometry using arachidonic acid, adenosine diphosphate and thrombin receptor-activating peptide as agonists. Concentrations of extracellular vesicles from all platelets (CD61+), activated platelets (CD62P+), leukocytes (CD45+) and endothelial cells (CD146+) will be analysed in platelet-depleted plasma using flow cytometry (A-60 Micro). Platelet-rich thrombus formation will be measured using whole blood perfusion system. The study will determine the antiplatelet effect of prostacyclin analogues and compare different prostacyclin analogues head-to-head to identify the best drugs to use in case of thrombosis or bleeding.