PARTICLE MOTION WITHIN IN-VITRO MODELS OF STENOSED INTERNAL CAROTID AND LEFT ANTERIOR DESCENDING CORONARY-ARTERIES

Asymmetric 75% and 95% area reduction, transparent Sylgard stenotic mo dels were operated under internal carotid artery (ICA) (Womersley para meter, alpha=5.36, Re-mean =213 and 180, respectively, and Re-peak=734 and 410, respectively) and left anterior descending coronary artery ( LAD) flow wave forms (alpha=2.65, Re-mean=59 and 57, respectively, and Re-peak= 137 and 94, respectively) to evaluate the effect of these co nditions on particle residence times downstream of the stenoses. Amber lite particles (1.05 g/cm(3), 400 mu m) were added to the fluid to sim ulate platelets and their motion through the stenotic region and were traced using a laser Light sheet flow visualization method with pseudo -color display. Two-dimensional (2D) particle motions were recorded an d particle washout in the stenotic throat and downstream section were computed for all cases. All four model cases demonstrated jetting thro ugh the stenosis which followed an arching pattern around a large sepa ration zone downstream. Considerable mixing was observed within these vortex regions during high flow phases. particle washout profiles show ed no clear trend between the degrees of stenosis although particles d ownstream of the stenoses tended to remain longer for LAD conditions. The critical washout cycle (1% of particles remaining downstream of th e stenosis), however, was longer for the 95% stenoses cases under each flow condition due to the larger protected region immediately downstr eam and maximal for the LAD 95% case. Results of this study suggest th at particle residence times downstream of 75% and 95% stenoses (simila r to 3-6 s for ICA and similar to 8-10 s for LAD) exceed the minimum t ime for platelet adhesion (similar to 1s) for at least 1% of cells and , thus, may be sufficient to initiate thrombus formation under resting conditions. (C) 1998 Biomedical Engineering Society.