Design investigation of a compliant vascular prosthesis

Abstract

For many years, stenting and coronary artery bypass grafting (CABG) have been the treatment for coronary heart disease. Despite the presence of metal stents, restenosis will occur to about 15% to 30% of the patients. Some patients require more than one bypass grafts or do not have suitable autologous vessels for this procedure. Therefore, an effective smaller diameter vascular prosthesis is required for these patients. Vascular graft failure is often caused by compliance mismatch between the grafted artery and prosthesis. With the aim to minimise the mismatch, Poly-Caprolactone (PCL) and Poly (L-Lactide-co-e-caprolactone) (PLC) are two popular materials used in research for the fabrication of vascular prosthesis. In our earlier work, we proposed a printed mesh design with tuneable geometric mechanical properties known as HEX-fiber design and the full structure is known as the J-mesh. Vascular prostheses of PLC tubes wrapped with PCL meshes were fabricated by dip-coating, followed by 3D printing. Finite Element Analysis (FEA) through in-silico assessment was done to test the behaviour of the folding and unfolding of mesh structures. The behaviour of how the PCL fiber extends through hydrostatic force is also studied through the compliance test. However, in an attempt to improve on the compliance of the meshes, the desired cross-section of the meshes have to be more circular. It was hypothesised that different fabrication method or printing parameters will affect the folding and unfolding behaviour of the fibers during compliance testing. In this study, an FEA was performed to justify the mesh design, followed by the optimization of CNC melt printing method was established coupled with different printing parameters of 3D biomimetic printing to create the J-mesh. The results have shown that the meshes printed from CNC printed machine showed some form of compliance matching while the printing of the J-mesh exhibited some form of compliance above 200 mmHg. Various areas of improvement on printing optimization of the bioprinter can be used to achieve compliance matching with native arteries.