VASCULAR BIOLOGY Brief report Valves of the deep venous system: an overlooked risk factor

Deep venous valves are frequent sites of deep venous thrombosis initiation. How-ever, the possible contribution of the val-vular sinus endothelium has received little attention in studies of thrombosis risk. We hypothesized that the endothelium of valve sinus differs from that of vein lu-men with up-regulation of anticoagulant and down-regulation of procoagulant ac-tivities in response to the local environ-ment. In pursuit of this hypothesis, we quantified endothelial protein C receptor (EPCR), thrombomodulin (TM), and von Willebrand factor (VWF) by immunofluo-rescence in great saphenous veins har-vested at cardiac bypass surgery. We found significantly increased expression of EPCR and TM in the valvular sinus endothelium as opposed to the vein lume-nal endothelium, and the opposite pattern with VWF (paired t test for TM and EPCR, each P <.001; for VWF, P .01). These data support our hypothesis and suggest that variation in valvular sinus thrombore-sistance may be an important factor in venous thrombogenesis. (Blood. 2009; 114:1276-1279