Consideration of suture line stresses in the selection of synthetic grafts for implantation

The failure of synthetic vascular grafts as a result of anastomotic rupture is common and most likely due to high stress concentrations at the suture line between graft and host-artery. Recent reports of large diametral variations (> 10 per cent) for major arteries and small distensions reported on arterial grafts (< 1 per cent), indicate that the artery can be considered clamped to a rigid graft. Mathematical analysis of the graft vs artery distension differences as presented in this paper show that even small differences in diameter cause large stress concentrations at the anastomoses. Using stress analysis these stresses have been calculated under hypertension for arterial pressures in the range of 160-190 mm Hg. It is shown that the shear stress at the anastomoses will be zero, and the axial stress at this site will be compatible with that normally found in the arterial wall of a healthy artery, when the graft/host-artery ratio is in the range 1·4-1·5.