Platelet dysfunction followed by thromboembolic as well as bleeding complications are severe events in patients with ventricular assist devices (VADs). Microparticles (MP) are cell vesicles with inflammatory and coagulatory potency that are released by cells during activation and can be used as specific cell activation markers. The aim of the study was to establish MP as surrogate markers for platelet, leukocyte and endothelial activation in VAD patients predicting platelet activation and vascular inflammation. Therefore, MP from platelet, leukocyte and endothelial origin were measured in 12 patients with VAD and compared to controls. VAD patients had significantly increased levels of platelet microparticles (PMP) (VAD 1705+/-1100 cpm vs. co: 527+/-238 cpm, P=0.002), leukocyte microparticles (LMP) (VAD 43+/-16 cpm vs. co: 18+/-8 cpm, P<0.001) and endothelial microparticles (EMP) (VAD 135+/-66 cpm vs. co: 46+/-23 cpm, P<0.001) indicating enhanced vascular inflammation and pro-coagulation. Furthermore, LMP correlated well to EMP suggesting that LMP induce endothelial cell dysfunction. In conclusion, VAD patients suffer from enhanced platelet, leukocyte and endothelial activation that can be easily quantified by measuring PMP, LMP and EMP and that may help to estimate the thrombotic risk and contribute to avoid ischemic but also bleeding complications.