Hemodynamics at stenoses formed by growing platelet thrombi in mesenteric microvasculature of rat.

Quantitative analyses of the dynamics of stenosis development were expressed in terms of the time course for changes in blood flow velocity in a stenosed region and thrombus configuration in the microvasculature of rat mesentery. The platelet thrombus was induced in microvessels by irradiation of filtered light in combination with intravascular administration of fluorescent dye. The blood flow velocity began to increase soon after the initiation of thrombus formation and continued to increase progressively with the growth of the thrombus in the radial direction. After the velocity reached an almost constant level, the velocity fluctuation became significant due to the frequent detachment of platelet aggregates. Meanwhile, the blood flow velocity precipitously dropped. Two different definitions of a critical stenosis were proposed. The first definition was the condition that the blood flow velocity reached a maximum. The critical area stenosis based on this definition had almost a constant value, i.e., 75-95% of the lumen area. The second definition of critical stenosis was given as the condition that the blood flow rate decreased by more than 15%. In the higher velocity range the values of critical stenosis based on the second definition were almost constant, i.e., 70-90% of the lumen area. However, in the lower velocity range, the critical condition seemed to occur in smaller stenosis.