Static Mechanical Properties of Helically Constructed Polyurethane Vascular Grafts Before and after Implantation

The influence of mechanical properties on the acute and chronic success of vascular grafts remains the subject of considerable debate. It is widely held that the matching of some set of mechanical properties at the anastomosis between a natural vessel and a vascular graft will optimize the likelihood of clinical sucess. Investigations in this area have largely concentrated on compliance (defined as the percentage change in diameter per unit change in pressure) as the parameter to be matched across the anastomosis. However, compliance represents only one out of a set of candidate parameters (including elastic moduli, Poisson ratios, admittance, distensibility, and hydraulic impedance among others) and there is no definitive evidence that it is in any way the most important mechanical parameter to be considered. As well, the concentration on compliance has resulted in the failure to examine the importance of the longitudinal behavior of the vascular grafts. The longitudinal properties of any vessel can profoundly influence the observed circumferential behavior; however, this is, at best, only implicit in the onedimensional compliance parameter.