Experimental Ultrasonographic Study The Relation Of Flow Shear Stress And Artherosclerosis

ObjectiveThe fluid shear stress was inspected in different time in rabbits with artherosclerosis (AS) by ultrasonography, to investigate the relation between shear stress and AS.Methods1.20 male New Zealand rabbits were fed with high cholesterol diet to artherosclerosis model rabbits.2. At the 0th, 4th, 8th and 12th week of the experiment, Philips HDI-5000 color doppler ultrasound was used to observe the image of abdominal aorta in rabbits. The hemodynamic parameters were measured, include: systolic peak velocity (Vs), mean velocity (Vm), diastolic dimension, intima-media thickness of abdominal aortic posterior wall,etc.3. As well, 4ml/5ml blood was taken from the vein of ear and blood lipid (total cholesterol and low density lipoprotein cholesterol and high density lipoprotein cholesterol) and hemorheological parameters were detected.4. Shear stress was calculated according to this equationτm=4×η×Vm/Dr.5. Relationship was assessed between IMT and shear stress in the 12th week.6. Meanwhile, three rabbits were executed in different time. Arteria were taken out and observed by electron microscope and light microscope.Results1. Intima-media thickness of abdominal aorta had no significant changes at the 4th week(p>0.05), then added gradually(p<0.01); diastolic dimension had no significant changes in the whole time.(P>0.05)2. The level of blood lipid (TC and LDL)was higher at the 4th week, up to highest at the 8th week, then reduced ,but still higher than 0 week at the 12th week(p<0.01). The lever of HDL is highest at the 4th week, then reduced gradually, but still higher at the 12th week than 0 week (p<0.01)3. The hemorheological indexes of blood viscosity and RBC aggregation index increased gradually (p<0.001), RBC deformation index reduced gradually (p<0.01).4. Shear stress decreased at the 12th week than 0 week (p<0.05), and there was a negative correlation between shear stress and IMT (r=–0.91, P<0.01).5. By light microscope, at the 4th week the structure of the abdominal aorta were normal, endothelium cell partly shed and elastic layer broke at the 8th week. By electron microscope, the cell organs of endothelium cell had changed at the 4th week.Conclusion1. Hypercholesterolemia is an important danger factor of AS.2. At the 12th week shear stress decreased and was negatively correlated to IMT, which was responsible for atherosclerosis.3. Ultrasonography is an effective method to evaluate flow shear stress,Shear stress could be an index of early diagnosing atherosclerosis.