Effect of wall shear stress on intimal hyperplasia distribution: An in vivo study.

摘要

Atherosclerosis is the leading cause of mortality in the United States. The primary treatment for correcting the effects of atherosclerosis is Vascular Bypass Grafting. Over time, vascular bypass grafts can fail due to a disease process known as intimal hyperplasia (IH), possibly initiated by hemodynamics. Several factors have been shown to influence the hemodynamics in and around the distal anastomoses of vascular grafts, including potency of the stenosis in the recipient artery. The purpose of this study was to determine the effect of stenosis grade in the recipient artery upon hemodynamics and the development of IH within distal anastomoses of chronic animal models.; Six (6) cm segments of e-PTFE grafts (I.D = 6 mm) were implanted for twelve weeks in each of the common carotid arteries of canines with a 20° end-to-side anastomosic angle. Varying grades of stenoses (50%, 65% and 100% by area) were created three diameters upstream of the distal anastomosis using a nylon cable tie. Axial flow velocities were simultaneously measured in vivo using a custom-made pulse ultrasonic Doppler wall shear rate measuring device at multiple axial locations at the time of graft implantation.; Overall, significantly more IH was observed in the totally occluded case as compared to the partially occluded cases. No significant differences were observed between the partially occluded cases. Hemodynamic patterns indicated low wall shear in the region upstream of the toe. The wall shear stresses increased dramatically as the flow moved downstream. Regression analysis indicated a weak correlation (r = 0.165) between wall shear stress and IH; however below a critical shear stress level the majority of IH occurred.