Simulation and analysis of aortic bypass surgery using computational fluid dynamics

Cardiovascular diseases (CVD) are the leading cause of death. The aorta is the major artery that carries blood from the heart to the body. Among these CVD narrowing of aorta is very serious condition. Bypass vascular surgery is done to restore blood flow through narrowed aorta to the vital organs and tissues. The success of operation for patients with CVD relies on vascular surgeons training, past experience etc. So it is very difficult to predict the surgical outcome of the patient. A Computed Tomography (CT) image of an Indian male patient, aged 64 year was obtained and three-dimensional model of aorta was obtained using Materialise's interactive medical image control system (MIMICS) software. Using the measured morphometry of the aorta from the three-dimensional model, the computer aided design (CAD) models of the following were created using an AutoDesk Inventor Professional software: i) normal aorta; ii) aorta with plaque at descending side; and iii) aorta with bypass graft. CFD analysis of the aorta was carried out using ANSYS software. The various parameters such as velocity (ms-1), pressure (Pa) and wall shear stress (Pa) that affects the blood flow on all the three CAD models were measured. In the aorta with bypass graft model, the percentage difference in the mean blood velocity was -3.8% only when comparing with normal one, and the percentage difference in the mean pressure was found to be +66.6%. The WSS was found to be same in both graft model and in the normal aorta model. Thus the measured CFD parameters were found to be same in both graft model and normal one, except the blood pressure and it was found to be 3-fold times higher in graft model than in normal. It may be due to the diameter and angle of the graft attached at the aorta, and hence it was greater at the graft side. Further studies may be required to identify the optimum designing of the graft in order to restore the normal functions of the aorta.