Stasis-Induced Thrombosis Wessler Model

Thrombus score is expressed as median (minimum-maximum). Thrombus weight is given as mean SEM. For the statistical evaluation of the antithrombotic effect, the nonparametric U-Test of Mann and Whitney (thrombus score) or Student s t-test for unpaired samples (thrombus weight) is used. Significance is expressed as p 0.05. 

CRITICAL ASSESSMENT OF THE METHOD Breddin (1989) described the Wessler model because of its static character as the retransformation of an in vitro experiment into a very artificial test situation. One of the major drawbacks is the relative independence of platelet function and hemodynamic changes that largely influence thrombus formation in vivo. However, the model has been shown to be very useful for evaluation of the antithrombotic effect of compounds like heparin and hirudin. 

There are a number of different procoagulant agents which had been used to induce thrombosis in this model, such as human serum, Russel viper venom, 

The general drawback of the Wessler model is the static nature of the venous thrombus development. To overcome this problem some investigators have developed more dynamic models with reperfusion of the occluded vessel segments after clot development. Depending on the time of test compound administration (pre- or post-thrombus initiation), the effect on thrombus growth and fibrinolysis can be evaluated. Levi et al. (1992) have used this model to assess the effects of a murine monoclonal anti-human PAI-1 antibody and Biemond et al. (1996) compared the effect of thrombin and factor Xa inhibitors with a low molecular weight heparin. 

Aronson DL, Thomas DP (1985) Experimental studies on venous thrombosis effect of coagulants, procoagulants and vessel contusion. Thromb Haemost 54 866-870 Biemond BJ, Friedeiich PW, Levi M et al. (1996) Comparison of sustained antithrombotic effects of inhibitors of thrombin and factor Xa in experimental thrombosis. Circulation 93 153-160 

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