Endogenous Thrombin Generation Potential in Patients with Pulmonary Embolism and Its Relevance to Thrombo-Inflammatory Biomarkers

Background: Pulmonary embolism (PE) is a catastrophic outcome in patients with venous thrombosis and third leading cardiovascular cause of death after myocardial infraction and stroke, estimates around 100,000 deaths annually.Inflammation, hemostatic dysregulation including fibrinolytic imbalance, endothelial compromise, and generation of thrombotic mediators, along with cellular defects and hemodynamic derangement contribute to the pathogenesis of PE.Endogenous thrombin generation contributes to the overall pathology of PE. The purpose of this study is to investigate endogenous thrombin potential (ETP) and the circulating biomarkers of fibrinolytic, inflammatory, and endothelial dysfunction in PE samples.

Methods: Citrated blood samples from 400 patients with confirmed PE were collected at Loyola University Medical Center and Gottlieb Memorial Hospital under an IRB approved protocol. Normal human plasma (NHP) comprised of 25 male and 25 female samples were obtained from a commercial source. Thrombin generation studies were carried out using a commercially available a kinetic system. Endogenous GAG's contents were measured by fluorogenic quenching method. Thrombin generation parameters such as peak thrombin, lag time and area under the curve (AUC) were compiled. Plasma samples were retrospectively analyzed for biomarkers, including D-Dimer, PAI-1, tPA, TAFIa, vWF, CRP, IL6, TFPI and VEGF using commercially available sandwich ELISA methods. Results were compiled as mean ± SD and analyzed for significance and correlation by using GraphPad Prism software.

Result: On a cumulative basis, PE patients showed a wide variation in thrombin generation parameters (Table 1). Biomarker analysis showed elevated levels of D-Dimer (37.05-fold), CRP (35.34-folds), IL6 (21.62-folds), tPA (4.69-folds), PAI-1a (3.95-folds), VEGF (2.38-folds), TFPI (2.17-folds), GAG's (1.92-folds), vWF (1.89-folds), and TAFIa (1.21-folds). Peak thrombin levels exhibited varying degree of positive and negative correlations with various biomarkers as illustrated in figure 1. Thrombin levels showed significant negative correlations with tPA, endogenous GAG's & TFPI, while positively correlated with VEGF. D-dimer showed positive correlations with CRP & IL6. PAI-1 demonstrated positive correlations with tPA, IL6, and endogenous GAG's. tPA showed negative correlation with TAFI, while positive correlations with endogenous GAG's, and TFPI. vWF showed positive correlations CRP, IL6, and endogenous GAG's. CRP showed positive correlations with IL6. Endogenous GAG's showed positive correlations with TFPI while TFPI showed negative correlation with VEGF.

Conclusion: PE patients exhibit a wide variation in endogenous thrombin generation parameters. Overall, peak thrombin and ETP were decreased, whereas the lag time was increased. The increase in thrombo-inflammatory markers is suggestive of upregulation of thrombogenesis, and inflammatory processes in these patients. Thus, the profiling of thrombo-inflammatory biomarkers along with thrombin generation profile may provide additional information on the pathogenesis and severity of PE. However, biomarkers of hemostatic activation, vascular dysfunction and inflammation were increased.

Monreal:Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Presented to congress, Research Funding; Leo Pharm: Research Funding; Rovi: Research Funding.