Hemocoagulation - New views on the old cascade

The process of hemocoagulation can be generally divided into the following stages: initiation, amplification, propagation and stabilization of thrombus. The most important changes of the hemocoagulation scheme accepted so far concern the position and generally the existence of the coagulation system external and internal branches, the central role of a tissue factor in initiation of hemocoagulation and the newly understood roles of factors XI and XII. Newly an active role of monocytes, leukocytes, erythrocytes and endothelial cells and their receptors in hemocoagulation has been identified, as well as the role of circulating microparticles which transfer some agents and information. The changed scheme of hemocoagulation also reflects the emerging possibilities of anticoagulation with a more favourable proportion of anticoagulation properties to the risk of bleeding and thrombotic events. Over the long term it is increasingly evident that both the internal and external branches of the coagulation system are initially launched through release of an active tissue factor, formation of a complex of a tissue factor with factor VIIa and ensuing activation of factor X on Xa. At the same time the role of factor XII in the intrinsic coagulation system is questioned, its role has now been experimentally proven together with factor XI in propagation and with factor XIII in the final strengthening of thrombus and when seeking new antithrombotic drugs it might be just its blocking which could meet the requirement on high effectiveness with minimum bleeding complications.

Keywords: hemocoagulation; hemocoagulation cascade; microparticles; new antithrombotic drugs; tissue factor; internal branch of coagulation system; external branch of coagulation system