Factors influencing the level of circulating procoagulant microparticles in acute pulmonary embolism

Summary Background Flow cytometry has shown levels of platelet-derived microparticles (PMPs) and endothelial-derived microparticles (EMPs) to be elevated in deep-vein thrombosis. Cardiovascular risk factors can also contribute to hypercoagulability due to circulating procoagulant microparticles (CPMPs). Aims To investigate in a case-control study the respective contribution of pulmonary embolism and cardiovascular risk factors to the level of hypercoagulability due to CPMPs. Methods CPMP, PMP and EMP levels were measured in 45 consecutive patients (age 67.9 ± 11.6 years; 66.7% men) admitted to an intensive care unit for acute pulmonary embolism (APE), 45 healthy control subjects with no history of venous thromboembolism or vascular risk factors (Controls noCVRFs ), and 45 patients with cardiovascular risk factors (Controls CVRFs ). APE was diagnosed by spiral computed tomography or scintigraphy. CPMP levels were assessed using a prothrombinase assay on platelet-depleted plasma (results expressed as nmol/L equivalent). Results CPMP levels were higher in APE patients than in Controls noCVRFs (medians 4.7 vs 3.2 nmol/L, interquartile ranges [IQRs] 2.9–11.1 vs 2.3–4.6 nmol/L; p  = 0.02). Similar results were reported for PMPs (medians 2.2 vs 1.9 nmol/L, IQRs 1.7–5.8 vs 1.4–2.4 nmol/L; p  = 0.02), whereas EMP levels were not significantly different. However, CPMP procoagulant activity was not significantly different in APE patients and Controls CVRFs . Conclusions CPMPs and PMPs were significantly elevated in APE patients vs Controls noCVRFs , but this correlation was not significant when APE patients were compared with Controls CVRFs . Our observations highlight the importance of adjusting for the presence of cardiovascular risk factors in conditions in which microparticle levels are raised.