Introduction: The success of LVADs has been limited by hemorrhagic and thromboembolic complications. Understanding the timing of changes in the endothelial and coagulation systems in LVAD patients may allow for potential therapeutic interventions. Methods: Markers of endothelial dysfunction (circulating endothelial cells [CEC], VCAM-1, E-selectin, von Willebrand antigen [VWA]), thrombin generation (prothrombin fragments 1,2 [PF1+2] and thrombin antithrombin [TAT]), and fibrinolysis (D-dimer) were studied in 20 LVAD patients on day 0 and on post-op days 1, 7, 30 and 90 as well as in 5 control patients undergoing non-LVAD cardiac surgery. Results: Baseline values of VCAM-1, E-selectin, TAT, VWA and D-dimer were significantly higher than the normal range in LVAD patients. Further evidence of endothelial and procoagulant pathway activation were seen on post-op day 1 and day 7. D-dimer, a marker of fibrinolysis, showed significant increase on day 7 and remained elevated up to day 90 while procoagulant and endothelial cell markers decreased significantly by day 30 (Table ). In control patients, baseline levels of D-dimer, TAT, VCAM-1, E-selectin were lower and declined significantly by day 7 as compared to LVAD patients ( 2-sample t-test p values < 0.05). Conclusions: LVAD patients show significant baseline activation of endothelial and coagulation systems which are further accentuated in the early post-op period. Persistent activation of the fibrinolytic system may allow for reduction of anticoagulation therapy in these patients. Further understanding of these abnormalities is essential to improve outcomes after LVAD placement. Table: Changes in Endothelial and Coagulation function markers in LVAD patients