An evaluation of the procoagulant action of recombinant activated factor VII in cord whole blood versus adult whole blood using thromboelastography

The thromboelastography G parameter as a potential biomarker of acute coronary syndrome

The most prominent event that defines acute coronary syndrome (ACS) is the formation of an intra-arterial thrombus, usually resulting from activation of platelet and fibrinogen at the ruptured plaque. Usually, conventional coagulation tests (CCTs) are used to estimate the hemostatic properties of patients. However, CCTs have significant limitations because they each assess individual aspects of the coagulation cascade, which is a complex multifaceted process. And CCTs are performed with platelet-poor plasma, while the contribution of platelets to clot formation is not measured. In contrast, thromboelastography (TEG) is a test for global hemostasis with whole blood, from the beginning of coagulation through clot formation to the ending with fibrinolysis. The aim of this study was to investigate whether TEG parameters could be surrogate biomarkers of thrombus formation process and diagnosis of ACS. Receiver operating characteristic（ROC）curve was used to evaluate the diagnosis performance of each index. Logistic regression analysis was utilized to define the independent risk factors of ACS. The results showed that the shear elastic modulus parameter (G) was an independent diagnostic indicator for ACS (odds ratio [OR], 2.600; 95% confidence interval [CI], 2.035-3.322). The area under ROC curve of G was 0.866. The optimal cut-off value for the diagnosis of ACS was 10.55 dyne/cm², while the sensitivity was 66.2% and the specificity was 92.4%. In conclusion, G could be used as an optimal indicator of activation of platelet and fibrinogen, which is eligible to be a useful biomarker for early diagnosis of ACS.

Characterization of In Vitro Hemostatic Peptide Effects by Thromboelastography

In this study, we validated a thromboelastography (TEG) method to evaluate the hemostatic effects of 3 peptides. The first peptide is an ideal amphipathic peptide composed of 22 leucine and lysine in a ratio of 2:1. At a very low concentration, the peptide had a procoagulant effect shown by decreases in reaction time (R) and coagulation time (K) but was impaired by a decrease in maximum amplitude (MA). At higher concentrations, the peptide had an anticoagulant effect. The α angle was minimally affected by the peptide. The second peptide is melittin derived from bee venom. Melittin showed procoagulant effects reflected by a decrease in clotting time but led to lower MA. The third peptide derived from fibrinogen γ chain promoted hemostasis only at an optimal concentration and became anticoagulant at a higher concentration. The hemostatic mechanisms of each peptide were discussed. Our study would facilitate further development of peptides for either hemorrhage control or thrombosis treatment.

Collagen/endogenous thrombin-induced platelet aggregation in whole blood samples

The aim of the study was to investigate the individual and combined effects of collagen (3.5 microg/ml) and endogenously generated thrombin (due to addition of 0.35 pmol/l tissue factor) on platelet aggregation in the physiological environment of whole blood by means of the impedance method. Lag times were significantly shorter when a combination of collagen and endogenous thrombin was used to provoke platelet aggregation (41.9 +/- 16.3 s) compared with collagen (173.8 +/- 52.1 s, P < 0.0001) or endogenous thrombin (94.3 +/- 43.6 s, P < 0.001). Amplitudes and slopes were the lowest in collagen-induced experiments (2.83 +/- 1.59 Omega and 1.79 +/- 0.45 Omega/min, respectively), whereas they were approximately the same in endogenous thrombin-induced experiments whether collagen was present or not (13.7 +/- 3.1 versus 11.2 +/- 4.0 Omega and 6.3 +/- 2.8 versus 5.6 +/- 2.3 Omega/min, respectively). No synergistic effect of collagen and endogenous thrombin on the clot formation process was observed by means of thrombelastometry. Moreover, thrombin potentials in tissue factor-activated plasma samples were approximately the same whether collagen was present or not (834 +/- 67 versus 809 +/- 63 nmol/l.min). In conclusion, endogenously generated thrombin is a potent platelet agonist in whole blood, and a combination of collagen and endogenous thrombin synergistically shortens the lag time until the onset of platelet aggregation.