Ben Ahmed S, Dillon-Murphy D, Figueroa C A
Department of Surgery, University of Michigan, Ann Arbor, MI, USA; CHU Clermont-Ferrand, Department of Vascular Surgery, F63003 Clermont-Ferrand, France.
Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
Eur J Vasc Endovasc Surg. 2016 Dec;52(6):736-745. doi: 10.1016/j.ejvs.2016.07.025. Epub 2016 Aug 23.
OBJECTIVE/BACKGROUND: Several risk factors have been identified in type B aortic dissection (TBAD), namely tear size, location, patency and number, and false lumen (FL) location. However, the individual impact of each of these factors is poorly understood. The impact of these factors was investigated using computational fluid dynamics (CFD).
Fourteen idealized models of chronic TBAD were created of different shapes (straight vs. curved vessels), different number of proximal and distal tears, tear size (4, 10, and 20 mm diameter) and shape (circular or elliptical), FL location (inner or outer arch), treated (stented), and untreated. All models had identical length, relative size of true lumen (TL) and FL, and inlet (flow) and outlet (pressure) boundary conditions. Using validated CFD tools, inlet mean pressure (MP), pulse pressure (PP), TL and FL pressures, velocities, and flows were computed for each model.
AD increased PP and MP relative to undissected aorta. Curvature did not change pressure and flow ratio between TL and FL. Inner curvature FL showed slightly larger pressures and tear velocities. Larger tears decreased hemodynamic differences between TL and FL. The combination of proximal and distal tear size determines the overall hemodynamics: larger proximal tears increased FL PP by up to 76%. Conversely, larger distal tears decreased FL PP and MP. Large proximal and distal tears decreased tear velocity (by up to 65%) and increased FL flow (up to 12 times). Proximal tear stenting resulted in a 54% reduction of PP. Conversely, distal occlusion tear increased FL PP and MP by 144% and 7%, respectively.
Unfavorable hemodynamic conditions such as larger FL pressure occur when distal tear is small or absent, proximal tears are large, and FL is at the inner curvature, in agreement with previous clinical studies. CFD analysis is a powerful tool to understand the interplay between anatomy and hemodynamics in TBAD.
目的/背景：B型主动脉夹层（TBAD）已确定了几个风险因素，即破口大小、位置、通畅情况及数量，以及假腔（FL）位置。然而，对这些因素各自的个体影响了解甚少。利用计算流体动力学（CFD）研究了这些因素的影响。
创建了14个慢性TBAD的理想化模型，这些模型具有不同的形状（直管与弯管）、不同数量的近端和远端破口、破口大小（直径4、10和20毫米）和形状（圆形或椭圆形）、FL位置（内弓或外弓），分为已治疗（置入支架）和未治疗组。所有模型具有相同的长度、真腔（TL）和FL的相对大小，以及入口（血流）和出口（压力）边界条件。使用经过验证的CFD工具，计算每个模型的入口平均压力（MP）、脉压（PP）、TL和FL压力、速度及血流。
与未夹层的主动脉相比，主动脉夹层增加了PP和MP。曲率未改变TL和FL之间的压力及血流比值。内曲率FL显示压力和破口处速度略大。较大的破口减小了TL和FL之间的血流动力学差异。近端和远端破口大小的组合决定了整体血流动力学：较大的近端破口使FL的PP增加高达76%。相反，较大的远端破口降低了FL的PP和MP。大的近端和远端破口降低了破口处速度（高达65%）并增加了FL血流（高达12倍）。近端破口置入支架使PP降低了54%。相反，远端闭塞性破口使FL的PP和MP分别增加了144%和7%。
远端破口小或无、近端破口大且FL位于内曲率时，会出现如FL压力较大等不利的血流动力学状况，这与先前的临床研究一致。CFD分析是了解TBAD解剖结构与血流动力学之间相互作用的有力工具。
