Impedance of a fibrin clot in a cylindrical tube: relation to clot permeability and viscoelasticity.
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.
Thurston
G B
GB
Department of Mechanical Engineering, University of Texas, Austin 78712, USA.
Henderson
N M
NM
D001777:Blood Coagulation; D001809:Blood Viscosity; D004548:Elasticity; D005337:Fibrin / Q000502:physiology*; D018056:Hemorheology; D006801:Humans; D008433:Mathematics; D008955:Models, Cardiovascular; D010539:Permeability; D011673:Pulsatile Flow / Q000502:physiology; D013927:Thrombosis / Q000097:blood
D005337:Fibrin