In Vitro, Time-Resolved PIV Comparison of the Effect of Stent Design on Wall Shear Stress

The effect of stent design on wall shear stress (WSS) and oscillatory shear index (OSI) was studied in vitro using time-resolved digital particle image velocimetry (DPIV). Four drug-eluting stents [XIENCE V-A (R) (Abbott Vascular), TAXUS(A (R)) Libert,(A (R)) (Boston Scientific), Endeavor(A (R)) (Medtronic), and Cypher(A (R)) (J&J Cordis)] and a bare-metal stent [VISIONA (R) (Abbott Vascular)] were implanted into compliant vessel models, and the flow was measured in physiologically accurate coronary conditions featuring reversal and realistic offsets between pressure and flowrate. DPIV measurements were made at three locations under two different flow rates (resting: Re = 160, f = 70 bpm and exercise: Re = 300, f = 120 bpm). It was observed that design substantially affected the WSS experienced at the vessel walls. Averaged values between struts ranged from 2.05 dynes/cm(2) (Cypher(A (R))) to 8.52 dynes/cm(2) (XIENCE V-A (R)) in resting conditions, and from 3.72 dynes/cm(2) (Cypher(A (R))) to 14.66 dynes/cm(2) (VISIONA (R)) for the exercise state. Within the stent, the WSS dropped and the OSI increased immediately distal to each strut. In addition, an inverse correlation between average WSS and OSI existed. Comparisons with recently published results from animal studies show strong correlation between the measured WSS and observed endothelial cell coverage. These results suggest the importance of stent design on the WSS experienced by endothelial cells in coronary arteries.