Stress reduction by geometric compliance matching at vascular graft anastomoses

An analysis is presented of stresses developed with different junctional configurations of end-to-end vascular graft anastomoses with severe compliance mismatch. Junctions of circular transverse sections and junctions by bias cuts (beveled ends) are compared with an anastomosis of a graft constructed with an elliptical transverse section and a bevel end cut vessel. This latter substitutes midwall inextensional deformations for extensional deformations that occur with the former, conventional configurations. Applications to end-to-side anastomoses are also discussed. A range of parameters are considered: i.e., vascular wall thickness/radius ratios between 0.1 and 0.5, locations from the anastomotic plane between 1/2 and 3/2 times the vascular wall thickness, host vessel axial stretch by external forces between 0 and 15%, maximal vascular circumferential stretch distal from the anastomosis between 0 and 25%, and perimeter locations at the anastomotic junction between 0 degree and 90 degrees. The graft constructed with an elliptic cross-section developed peak stresses that are orders of magnitude lower than those developed with conventional configurations. The introduction of matching geometric compliance that dominates at the anastomotic junction minimizes consequences of material mismatch between graft and vessel and has the potential to reduce suture line stress greatly. This analysis may suggest designs for experimental studies to confirm relationships between neointimal hyperplasia and suture line stress levels, and provide a relatively simple solution for reduction of such stresses at the anastomotic junction. Choices may be permitted of graft materials with optimal surface properties despite less favorable elastic properties.