RELATIONS BETWEEN FLOW STRUCTURE AND VASCULAR PATHOPHYSIOLOGICAL CHANGES IN THE CARDIOVASCULAR SYSTEM --STUDIED BY ULTRASONIC DIGITAL FLOW IMAGING SYSTEM--

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Specific flow dynamics would play a significant role in the initiation and development of atherosclerosis. To elucidate the underlying mechanism of the atherogenesis with regard to local flow dynamics, we assessed the distribution of the wall shear stress in canine arteries by the high frequency multigate Doppler flowmetry, which allowed us to measure the instantaneous flow velocity profile in in vivo vessels. Then, we investigated the quantitative relation of the wall shear stress with the amount of the microfilament bundle in the endothelial cell as assessed by ultrastructual morphometry. After the left thoracotomy, the Doppler transducer was placed on the left anterior descending coronary artery (LAD), subclavian artery (SA), and thoracic descending aorta (DA) at the fixed angle (60 degrees), and the recording of flow velocity profile was performed in 5 dogs. The wall shear stress was determined as a product of the velocity gradient in the boudary layer and the kinematic viscocity o … More f the blood. After the Doppler examination, the studied vessels were perfusion-fixed under the constant pressure (100 mmHg), and the ultrastructural morphometric analysis was performed longitudinally and transversely in the length of 0.3mm in x17720 photos. The data are summerized in the following tables 1 and 2.Peak wall shear stress was signigicantly lower in LAD compared with those in SA and DA. However, the F/C ratio, the ratio of the area of microfilament bundle to the area of endothelial cell, was significantly greater in LAD than those in SA and DA. Thus, these results suggest that in physiological conditions the amount of the microfilament bundle in the endothelial cell, which is compatible with actin filament stress fiber, seems not to be determined only by the wall shear stress. The cytoskeletal structure of the coronary arterial endothelial cell is considered to be quite specific when compared with that in other artery, and this finding seems to be helpful in assessing the pathology of the coronay artery. Less