Department of Mechanical Engineering, National University of Singapore, Singapore.
Eur J Cardiothorac Surg. 2013 Apr;43(4):829-38. doi: 10.1093/ejcts/ezs388. Epub 2012 Jul 5.
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.
心血管疾病（如动脉粥样硬化和动脉瘤）与血流动力学因素密切相关，而血流动力学因素又受管腔几何形状的控制。本研究旨在研究衰老主动脉几何形状变化对血流动力学的影响。
从我们的医学数据库中选择了 6 名具有复杂几何特征的老年患者，如升主动脉膨出或扭曲、主动脉弓急剧弯曲和降主动脉双弯曲等。对这 6 例具有变异几何形状的主动脉进行重建，并通过计算流体动力学模拟研究这些特定于患者的主动脉模型中血流的脉动特性。为主动脉模型的各种动脉规定了真实的时变边界条件。
本研究表明，人体主动脉中的血液动力学高度依赖于几何形状。升主动脉的定位和轮廓可能与速度分布的偏斜有关。主动脉弓或弯曲处的流型通常偏向内弯曲壁，这种偏斜可能导致内弯曲壁处产生二次流。发现远端主动脉弓的涡度程度与弓曲率有关。当主动脉血液动力学开始出现左旋并在升主动脉中消失时，其螺旋性质在收缩期占主导地位，而右旋在远端主动脉弓中持续存在。在存在二次流的升主动脉区域也发现了较低的壁面剪切力。
具有不规则轮廓和较大弓部曲率的主动脉有利于发展主动脉内二次流，随后与动脉粥样硬化的发病机制有关。本研究确定了与各种局部几何特征相关的血液动力学行为的一般趋势。结合血液动力学与心血管疾病发展过程中潜在风险之间的相关性知识，我们的研究希望更好地理解主动脉形态与心血管疾病发展病理生物学之间的关系。因此，可以进行早期的医疗规划和手术干预，以延缓或预防心血管疾病的发展。
