Computational hemodynamic analysis of bypass graft for patients with severe femoral periphheral arterial disease

Abstract

Peripheral arterial disease (PAD) is a condition in which narrowed arteries reduce blood flow to the arms or legs. This may cause leg pain when walking (claudication) and other symptoms. PAD is usually a sign of a buildup of fatty deposits in the arteries (atherosclerosis). Atherosclerosis causes narrowing of the arteries that can reduce blood flow in the legs and, sometimes, the arms. Femoral-bypass surgeries are a common mode of treatment for those who are suffering from severe PAD. Neointimal hyperplasia (NIH) occurs when the innermost layer of arteries is abnormally thickened as a result of injury or certain medical procedures like bypass surgeries. As a result of NIH, the blood vessels can re-narrow again, which is known as restenosis. Hence, in numerical studies, the improvement of these hemodynamic factors has been utilized as an indicator to achieve superior geometries and higher patency rates for bypass grafts. This study aims to conduct a computational analysis of distinct anatomical and geometrical characteristics of grafts to determine optimal graft features for femoral bypass surgery, so that it helps vascular surgeons plan their surgery to achieve maximum favorable output from the procedure. To mimic the real-life scenario of blood flowing through the femoral bypass grafts and to acquire the hemodynamic parameters and resulting mechanical parameters, a computational fluid dynamics (CFD) system has been used throughout this dissertation. Clinical imaging modalities have been used in this study to attain the patient-specific models of arteries for computational analysis, which were used to create virtual femoral bypass surgery models. Parameters like wall shear stress (WSS), time average wall shear stress (TAWSS), oscillatory shear index (OSI), high oscillatory low magnitude shear (HOLMES), pressure drop, flow velocity, and average helicity have been measured to analyze the performance of the graft under different geometrical and anatomical variation. Through the results obtained in this research thesis, it shows that computational fluid analysis can be used in the medical field to aid doctors with helpful information and help them to serve their patients. Keywords: Peripheral Arterial Disease (PAD), Femoral bypass surgery, saphenous vein graft, PTFE graft, Taguchi method