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Abstract
Explanted extracorporeal access devices exhibit different degrees of thrombus formation as a result of different physiological factors in vivo. Numerous computational techniques have been developed to predict regions of thrombus formation based on mechanical factors. The prediction of thrombosis in these studies has been limited to isolated cases and specific conditions to validate their use. They have not been implemented for clinical applications and the impact of physiological factors has not been investigated. This thesis explored the effect of physiological factors on the likelihood of thrombus formation in an extracorporeal access device. Four physiological velocity waves (triphasic, biphasic, sharp monophasic, and blunt monophasic) were identified in the femoral artery as a result of different levels of peripheral arterial disease progression. The four waves were used to compare the effect of different pulsatile flow conditions on the likelihood of thrombus formation. This thesis also explored the effect of different geometrical design factors on the likelihood of thrombus formation to optimise its design. Computational fluid dynamics was used to simulate the flow conditions in an occlusive femoral artery with an attached extracorporeal access device. Residence time was used to predict the location and size of thrombus formation on the surface of the cavity. It was shown that the retrograde flow had a considerable impact on the likelihood of thrombus formation, which increased as the integrity of the physiological wave decreased. The predicted location of thrombus was always in the same location, but varied in size depending on the velocity wave. It was also shown that of the device design factors, the angle of the device has the greatest impact on the likelihood of thrombus formation. The computational results were compared to five explanted devices and demonstrated similar locations and sizes of thrombus formation. This thesis examined the likelihood of thrombus formation in a particular extracorporeal access device; however, the methods adapted are beneficial in a wider context and possess a clinical relevance to patient prognostics when prescribing the implantation of a medical device.