Effect of prolonged pulsatile shear stress in vitro on endothelial cell seeded PTFE and compliant polyurethane vascular grafts

Objectives: Compliance mismatch between graft and native artery, and failure of the graft to develop an endothelial lining are the two main factors in graft failure. The objective of this study was to assess a new compliant graft for effective cell attachment and cell retention at physiological levels of pulsatile shear stress over a 6-hour period of physiological pulsatile flow. Design: Laboratory haemodynamic study. Materials and Methods: Human umbilical vein endothelial cells labelled with In-111-oxine were seeded on compliant polyurethane (CPU) and polytetrafluoroethylene (PTFE) vascular grafts. These were then exposed to varying shear stresses of up to 23.8 +/- 0.6 dyn/cm(2) using a pulsatile flow model. Dynamic scintigraphy images were acquired using a gamma camera linked to an on-line computer during 6 h of perfusion and data presented as mean+/-standard error of mean. Results: Mean seeding efficiencies were significantly different at 4,316+/-505 and 825+/-504 CPM/cm(2) on the CPU and PTFE grafts, respectively (p = 0.018). The flow experiment showed a higher percentage of cells retained on the CPU graft after exposure to shear stress caused by pulsatile flow compared to PTFE with respect to time. After 6 h pulsatile perfusion there was a significantly higher proportion of initial cells attached to CPU graft compared to PTFE graft (73+/-8% vs 42+/-8%, p=0.018). The areas under the time activity curves over the 6-hour period were 280+/-26.4 for CPU and 176.0+/-30.0 for PTFE, confirming a significant greater fetal cell loss from PTFE compared with CPU grafts (51+/-7.0% vs 23+/-8.3%, p=0.018, Wilcoxon matched-pairs signed-ranks test). Conclusions: This flow model provides an effective method of assessing cell retention on graft materials under physiological conditions over a 6-hour period; CPU combines both excellent compliance and endothelial cell attachment rates after 6 h exposure to shear stress.