Recently we developed a damped oscillation type rheometer. This rheometer consists of a cylindrical tube filled with blood, suspended from a torsion wire. The tube is excited in torsional oscillation and subsequent damped osillation is observed. From damped oscillation curves measured at a certain interval, the change of logarithmic damping factor of blood during coagulation is measured.
Characteristics of the apparatus are follows; 1) the sensitivity is very high, that is, the detectable lowest value of viscosity is as low as 0.5 centi-poise and 2) the tube can be exchanged for one made of a different material with diffrent size. Therefore, it is expected that the apparatus is available for clinical test of blood coagulation and for in vitro evaluation of anti-coagulability and/or anti-thrombogenecity of artificial materials.
In this paper, to determine a tube material suitable for clinical uses, the change of logarithmic damping factor during coagulation for blood is compared among different kinds of tube material. It is concluded that the glass is one of the best material for the measuring cell in the present apparatus since it is possible to measure the whole coagulation prorecess including the initial stage and clot retraction in the glass tube. Also, analytical method of experimental data to evaluate anti-thrombogenecity or anti-coagulability of materials is descussed.

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We analyzed phasic blood velocities in small arteries and veins of the left atrium by using laser Doppler velocimetry. In anesthetized open-chest dogs, the left atrial appendage was gently displaced to observe small branches of the artery and vein (150-500 μm, outer diameter). The tip of the fiber-optic was fixed on the vessel surface with a drop of cyanoacrylate, and the blood flow velocity was measured through the wall. Phasic blood velocity waveform in atrial coronary artery showed a systolic predominant pattern which resembled the aortic pressure waveform, but was characterized by a pronounced “dip” during atrial contraction period. Administration of isoproterenol resulted in an increase in the acceleration rate and an appearance of reverse flow during atrial contraction phase. Typical vein velocity pattern showed a major peak flow during atrial contraction phase, accompanied by relatively small flow during atrial diastole. Isoproterenol increased the acceleration rate of forward flow. These results indicate that blood velocity waveforms of artery and vein of the atrium are quite different from those of the ventricle. The phase opposition between arterial inflow into and venous outflow from the atrial myocardium indicates that a large portion of the inflow is stored in the capacitance vessels during atrial diastole and myocardial contraction promotes venous outflow.

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