Tubular Nitinol Knit Meshes for External Reinforcement of Saphenous Vein Grafts: A Numerical Design Study

The difference in mechanical properties between grafts and host arteries is a complicating factor for vascular bypass surgery and can cause patho-physiological problems after implantation [1–7]. Diffuse and focal intimal hyperplasia, one of the key factors of vein graft failure, has been attributed to over-distension and diametric irregularities of the veins when exposed to the arterial circulation [8]. The external reinforcement of saphenous vein grafts with open-mesh knitted Nitinol structures is suggested to prevent over-distension, smooth the luminal diameter, and address the mismatch in mechanical properties of vein graft and host vessel. The objectives of this work were: 1) development of Finite Element (FE) models of knitted Nitinol structures to assess mechanical behaviour and structural properties, e.g. vascular compliance, and 2) proof of feasibility of the FE method developed for structural design optimisation of the Nitinol mesh.