Patient-specific, multi-scale modelling of neointimal hyperplasia in lower extremity saphenous vein grafts

Neointimal hyperplasia, a cardiovascular condition that develops consequently to vein graft surgery, is known to be largely affected by the haemodynamic behaviour of flow in the grafts. Its mechanisms are not yet completely understood, and in silico models can help to test hypotheses on the relationship between vein graft adaptation and haemodynamic forces, complementing the knowledge from traditional in vivo and in vitro experiments. In this thesis, the development and application of a multi-scale, patient-specific simulation framework to understand and model key properties of bypass failure due to hyperplasia is presented. The framework brings together mathematical techniques and biological data to produce a model of neointimal hyperplasia that describes the link between haemodynamic forces and significant biological mechanisms. It was developed using patient-specific imaging and haemodynamic data, which enabled to model in detail the characteristics of blood flow through the use of computational fluid dynamics simulations. In addition, it consists of a mathematical model describing the response of biological components to wall shear stress. The framework was tested on patient-specific data, with a thorough analysis of the results from the simulations. In addition, the model’s performance was assessed under different assumptions (different flow profiles, different models of viscosity, moving arterial walls), which enabled to draw conclusions on the optimal set of conditions for the framework. A key feature of this work is that the simulations presented here are compared against patient-specific clinical data, which constitutes a novelty in the context of neointimal hyperplasia and bypass failure.