Examples of the effects of pro- and anticoagulant agents on thrombodynamics results

Coagulation Factor Deficiencies

Factor VIII deficiency

In cases of hemophilia, i.e. deficiency of FVIII or IX, the intrinsic tenase does not work normally impairing propagation of the clot.

Comparison of thrombodynamics results for a patient with severe hemophilia A and healthy donor is shown.

Clot formation is initiated normally, but resultant clot growth is slow. Numerical parameters are shown in the table. V is decreased while Tlag does not change. 

Hemophilia A

Control

Fibrinogen deficiency

Formation of a fibrin clot is the final result of the coagulation cascade. If there is no fibrinogen present or the polimerization process is impaired, the density of the clot will change.

The thrombodynamics results for fibrinogen deficient plasma which was spiked with different concentrations of fibrinogen are shown below. In the case of deficiency no clot is observed, increases of fibrinogen concentration result in increases of clot density.

Fg deficiency

30 % of Fg

100 % of Fg

Procoagulant agents

Tissue factor

The presence of tissue factor (TF) in plasma increases clot growth rate and can result in the formation of spontaneous clots in the plasma.

[TF]=0,25 pM

Control

Factor VIIa

FVIIa is used as a bypassing agent in hemophilia treatment. It causes changes in clot formation similar to TF.

[VIIa] = 30 nM

Control

Factor XIa

If FXIa is present, the clot growth rate is increased and spontaneous clot formation is observed.

130 pM of FXIa

Control

Phospholipid surface and platelets

Most of the reactions of the coagulation cascade occur on phospholipid surfaces. In the thrombodynamics assay platelet free plasma (PFP) is used with no phospholipids added. But for some application it is possible to introduce additional phospholipid surfaces (PLS). For example artificial phospholipid vesicles or platelets.

If phospholipid vesicles are present, rate of FX and prothrombin cleavage is increased. This results in an increase of the rate of clot growth.

 4µM of PLS

Control

The assay can also be performed in platelet rich plasma. Platelets slightly increase the rate of clot propagation and can induce spontaneous clot formation.

 100×103 µ-1

PFP

Anticoagulant drugs

Heparin

Heparin in complex with antithrombin III inhibit activated factors II, X and IX.

Plasma results shown below are from a patient undergoing hip replacement surgery spiked in-vitro with heparin. The rate of clot growth decreases, while Tlag does not change. Spontaneous clotting is suppressed.

0,06 ME/ml of
heparin

Before heparin

Warfarin

Warfarin is vitamin K antagonist, which leads to decreased activity of factors VII, IX, X and II.

Warfarin

Control

Dabigatran

Dabigatran is a direct thrombin inhibitor. Intake of 220 mg of dabigatran leads to an increase of lag time and a decrease of the initial rate of clot growth.

3h after 220 mg of dabigatran

Before dabigatran

Rivaroxaban

Rivaroxaban is a direct FXa inhibitor. Intake of 10 mg of rivaroxaban leads to increase of lag time and a decrease of both the initial and stationary rates of clot growth.

2h after 10 mg of rivaroxaban

Before rivaroxaban