The influence of fibrin polymerization and platelet-mediated contractile forces on citrated whole blood thromboelastography profile

Thromboelastography analysis providing a global assessment of coagulation is gaining new interest in clinical practice. Minimal TF triggered whole blood thromboelastography provides a valuable tool for studying the kinetics of clot formation (expressed by the parameters R, K and alpha-angle) and the physical characteristics of the clot, such as its firmness and the elastic modulus shear (expressed by the parameters maximal amplitude MA and G). We studied the influence of fibrin polymerization and platelet functional status on each parameter of thromboelastographic trace obtained by minimal TF activation in WB by employing increasing concentrations of a fibrin polymerization inhibitors (the tetrapeptide Gly-Pro-Arg-Pro-OH.AcOH; Pefabloc-FG (R)) and an inhibitor of actin polymerization (Cytochalasin D). Pefabloc-FG (R) at concentrations higher than 5 mg/ml prolonged the R and K times and decreased the alpha-angle in a concentration-dependent manner but it did not modify MA and G parameters. At the concentration of 5 mg/ml, Pefabloc-FG (R) completely inhibited clot formation. Cytochalasin D had no effect on R time but decreased the alpha-angle, MA and G parameters by reaching a plateau at the concentration of 5 mu M. The effect of cytochalasin D was more pronounced on MA and G than on the alpha-angle. A combination of both Pefabloc-FG (R) (0.5 mg/ml) and cytochalasin D (50 mu M) significantly decreased a-angle compared to control as well as their single effect. However, G value was dramatically reduced in the presence of cytochalasin D exposure, without any additional effect when both inhibitors were combined. This study confirms the importance of fibrin polimerization on the kinetics of thrombus formation and demonstrates the close association between the quality of the thrombus and the functional status of platelets. Normal platelet contractile forces are of major importance for the maximum amplitude of TEG which is related to the strength and elastic modulus of the thrombus.