A computational fluid dynamics study on geometrical influence of the aorta on haemodynamics.

Cardiovascular diseases, such as atherosclerosis and aneurysm, are closely associated with haemodynamic factors that are governed by luminal geometry. The present work aimed to study the effect of geometrical variation of aging aortas on haemodynamics. Six aged subjects with intricate geometrical features, such as bulging or twisted supra-aortic arteries, sharply curved arch and double-curved descending aorta, were chosen from our medical database. These six geometrically variant aortas were reconstructed and the pulsatile nature of the blood flow of these subject-specific aorta models investigated using computational fluid dynamics simulations. Realistic time-dependent boundary conditions are prescribed for various arteries of the aorta models. This study suggests that haemodynamics in the human aorta is highly dependent on geometrical features. The positioning and contouring of the supra-aortic arteries may be associated with the skewness of velocity profiles. The flow profiles in the aortic arch or bends are generally skewed towards the inner curvature wall and this skewness may give rise to the formation of secondary flow in the inner curvature wall of the distal arch. The degree of vorticity in the distal aortic arch is found to be related to the arch curvature. The helical nature of aortic haemodynamics is predominant in the systole phrase when it begins with a left-handed rotation and then vanishes in the ascending aorta, whereas a right-handed rotation persists in the distal aortic arch. Lower wall shear stress is also found in the ascending regions where secondary flow is present. The aorta with an irregular contour and large degree of curvature at its arch favours the development of the intra-aortic secondary flow that subsequently relates to the pathogenesis of atheroma. The present study identifies the general trend of haemodynamic behaviours associated with various local geometrical features. Combining the knowledge of the correlation between haemodynamics and the underlying risks in the development of cardiovascular diseases, our study hopes to provide a better understanding of the relationship between aortic morphology and developing pathobiology of cardiovascular diseases. As such, early medical planning as well as surgical interventions can be designed to retard or prevent the development of cardiovascular diseases.