Dynamic viscoelasticity of blood during clotting in health and disease 1

Abstract

In the present study, an investigation was into the changes in viscoelasticity of the clot formed during the process of blood coagulation of normal subjects and of patients with a variety of disease, in an effort to elucidate the rheological aspect of a thrombus formation.

Dynamic viscoelasticity was measured by the viscoelastorecorder and was shown by absolute values, namely dynamic elastic modulus (E′) and loss modulus (E″).

Experimental conditions were: temperature, 25.0°C; oscillation of outer cylinder, 3 c/s, amplitude; 60 μm from peak to peak; and blood samples used diluted to 66.7 per cent of the original by adding citrate and CaCl₂ solutions which were used as an anticoagulant and for recalcification, respectively. Results of experiment were as follows:

(1) Average saturated dynamic elastic modulus (E′s) and loss modulus (E″s) of normal subjects were 3393 and 252 dyn/cm², respectively. High viscoelasticity of blood clot was often recorded in patients with connective tissue disease, neoplasm, hematological disease (polycythemia vera and chronic granulocytic leukemia), infection and diabetes mellitus.

(2) Investigation of causative factors of high E′s level. In high E′s group of patients, hematocrit was lower than that of the groups of which E′s was within normal limits, however, platelet count, plasma viscosity and erythrocyte sedimentation rate elicited high levels. Also, high E′s level was accompanied by high levels of maximum clotting gradient and E″s.

(3) Correlation of factors related to clot strength was studied. Good correlations were found in E′s vs MCG, E′s vs plasma fibrinogen, E′s vs E″s, and tan δ vs E″s.

(4) Effects of platelet on clot strength. In platelet rich plasma, levels of MCG, MCG′, E′s, E″s and tan δ were higher than those of whole blood or platelet poor plasma. It is of interest to note that tan δ was influenced by platelet count.