Experimental determination of velocity profiles and wall shear rate along the rabbit aortoiliac bifurcation: relationship to vessel wall low-density lipoprotein (LDL) metabolism.

We have determined the velocity profiles and wall shear rates along the New Zealand White (NZW) rabbit aortoiliac bifurcation. A pulsatile perfusion apparatus was used to impose physiologic pressure and flow waveforms on nine freshly excised NZW bifurcation segments. Pulsed Doppler velocimetry (PDV) was utilized to construct velocity profiles at five measurement sites: within the infrarenal aorta; immediately distal to the apex of the bifurcation; and, more distally along the iliac arteries. Wall shear rate was derived from a numerical differentiation of the experimental velocity profiles. The results of this study indicate that the average shear rate was lower along the lateral (approximately 40 s-1) vs medial (approximately 240 s-1) wall of the proximal iliac branch. The degree of flow reversal along the proximal lateral walls (20 +/- 2%) exceeded that along the proximal flow divider wall (1 +/- 1%). Flow at the distal iliac measurement sites and within the infrarenal aorta was approximately symmetric. These findings complement our companion in vivo study [Berceli et al., Arteriosclerosis 10, 688-694 (1990)] wherein we determined the rates of low-density lipoprotein (LDL) incorporation and catabolism along this symmetrically bifurcating conduit. Taken together, these studies provide original information regarding the effects of hemodynamics on one presumed atherogenic risk factor, namely, LDL metabolism.