Influence of blood cells and blood flow on venous endothelium : Venous wall and the etiology of varicose veins : New discoveries

: The principal emphasis in the past has been on the physical characteristics of the vein wall and to some extent the flow characteristics of the blood it contains. The interaction between the blood cells and the venous endothelium has been largely neglected until recently. This brief review summarises the secretion by the endothelium of such important substances as fibrinolytic agents, antiplatelet agents and venodilators. Many of these secretory activities are modulated by the wall shear stress which in turn is related to the rheological properties of the blood. The rheological properties of bulk venous blood have been shown to be significantly abnormal in patients with venous hypertension. Such haemodynamic and haemorheological alterations also play an important role in the interaction between the formed elements of blood and the vessel wall. Most recently this has assumed the importance in relation to the margination and adhesion of white cells to the endothelium and the subsequent activation of the white cells. Interaction between the circulatory blood and the venous endothelium probably plays an important role in the pathophysiology of both simple varicose veins and the more serious complications of venous disease such as thrombosis.