EFFECT OF CONTINUOUS ARTERIAL BLOOD FLOW ON THE WASHOUT BEHIND A STENOSIS IN THE CAROTID ARTERY:

In recipients of rotary blood pumps for cardiac assist, pulsatility of arterial flow is considerably diminished. This influences the shear stress patterns and streamlines in the arterial bed, with potential effects on washout and subsequent plaque growth. These situation may be even aggravated in the recirculation area behind a already pre-existing stenosis. In a previous study we have demonstrated (Int. J AO 2003, 152-60) that within normal conditions particle residence times are only little influenced by changing flow patterns. In the present study the 3D-computer model was applied to a massive stenosis (75%) in the carotic bulb. Four different flow characteristics (no support to full pump support) were applied. Flow patterns and particle residence time within the recirculation region (once within the whole area and once in a small region directly at the posterior stenotic heel) were calculated. Flow patterns showed a considerable radial vorticity behind the stenosis. Mean particle residence time in the whole recirculation region was 15% less for the continuous flow pattern compared to the natural flow pattern (0.19 compared to 0.22 sec), and nearly identical for the small heel region (0,28 to 0.27 sec). The flow simulation demonstrates, that even in the case of a pre-existing stenosis, the local effects of continuous flow on particle residence times are low (as it was previously shown already for intact arterial geometries). Therefore, from the standpoint point of flow field analysis, continuous flow should not enhance the thromboembolic risk in VAD recipients.