ON MATCHING COMPLIANCE BETWEEN CANINE CAROTID ARTERIES AND POLYURETHANE GRAFTS

Compliance mismatch between a host artery and an implanted graft has b een suggested as a contributing factor to a small diameter graft failu re. In this study, static compliance and dynamic compliance were defin ed and measured in vitro and in vivo for canine carotid arteries and 2 types of polyurethane grafts. Based on these compliance values, the c ircumferential modulus (E-theta) and longitudinal modulus (E-z) were c alculated. It was shown that grafts have constant moduli over a wide r ange of pressure while the moduli of carotid arteries increase signifi cantly with increasing pressure (dynamic E-theta from C.20 to 1.32 MPa ). Polyurethane grafts are nearly isotropic, with the modulus almost i dentical in each direction, while carotid arteries are anisotropic (Et heta/Ez = 2-3). The dynamic moduli are generally higher than static va lues and are especially pronounced for arteries. Due to these differen t inherent characteristics, the compliance of a synthetic graft may ma tch that of the host artery only in the circumferential direction and within a small pressure range. A stated limitation is therefore given for complete compliance matching. The results provide a rationale for identifying the degree of compliance match. These efforts may lead to better designed vascular grafts.