Impedance of a fibrin clot in a cylindrical tube: Relation to clot permeability and viscoelasticity

Article type: Research Article

Authors: Thurston, C.B. | Henderson, N.M.

Affiliations: Rheology Laboratory, Department of Mechanical Engineering, The University of Texas, Austin, TX 78712, USA

Abstract: By use of an impedance to quantify the pressure-to-flow relation for a clot-filled tube, a simple model is developed that encompasses both viscoelastic and porous properties of the clot. Measurements over a range of frequencies are used to separate the role of clot permeability from clot matrix elasticity. The theoretical impedance model consists of a series resistance and capacitance (representing structural flow) in parallel with a resistance (representing permeating flow). The viscoelasticity of the matrix, permeability and effective pore size are related to these three impedance elements. The validity of the model has been verified for a range of vessel sizes approximating small arteries (1 to 3 mm in diameter). The presence of dextran T40 in clotted fibrinogen solutions changes the clot impedance by increasing clot permeability and decreasing clot viscoelasticity. Because the flow contains two components, the behavior of a clot in vivo under pulsatile pressure cannot be predicted from the viscoelastic properties obtained from non-tube flow instruments nor from steady flow permeation measurements; a combination of the two as provided by oscillatory tube-flow measurements is required.

Keywords: Fibrin clots, impedance, permeability, viscoelasticity, rigidity

DOI: 10.3233/BIR-1995-32501

Journal: Biorheology, vol. 32, no. 5, pp. 503-520, 1995