Shuhaiber Jeffrey H, Niehaus Justin, Gottliebson William, Abdallah Shaaban
School of Aerospace Systems, University of Cincinnati, Cincinnati, OH, USA.
Interact Cardiovasc Thorac Surg. 2013 Aug;17(2):308-13. doi: 10.1093/icvts/ivt193. Epub 2013 May 9.
The theoretical differences in energy losses as well as coronary flow with different band sizes for branch pulmonary arteries (PA) in hypoplastic left heart syndrome (HLHS) remain unknown. Our objective was to develop a computational fluid dynamic model (CFD) to determine the energy losses and pulmonary-to-systemic flow rates. This study was done for three different PA band sizes.
Three-dimensional computer models of the hybrid procedure were constructed using the standard commercial CFD softwares Fluent and Gambit. The computer models were controlled for bilateral PA reduction to 25% (restrictive), 50% (intermediate) and 75% (loose) of the native branch pulmonary artery diameter. Velocity and pressure data were calculated throughout the heart geometry using the finite volume numerical method. Coronary flow was measured simultaneously with each model. Wall shear stress and the ratio of pulmonary-to-systemic volume flow rates were calculated. Computer simulations were compared at fixed points utilizing echocardiographic and catheter-based metric dimensions.
Restricting the PA band to a 25% diameter demonstrated the greatest energy loss. The 25% banding model produced an energy loss of 16.76% systolic and 24.91% diastolic vs loose banding at 7.36% systolic and 17.90% diastolic. Also, restrictive PA bands had greater coronary flow compared with loose PA bands (50.2 vs 41.9 ml/min). Shear stress ranged from 3.75 Pascals with restrictive PA banding to 2.84 Pascals with loose banding. Intermediate PA banding at 50% diameter achieved a Qp/Qs (closest to 1) at 1.46 systolic and 0.66 diastolic compared with loose or restrictive banding without excess energy loss.
CFD provides a unique platform to simulate pressure, shear stress as well as energy losses of the hybrid procedure. PA banding at 50% provided a balanced pulmonary and systemic circulation with adequate coronary flow but without extra energy losses incurred.
在左心发育不全综合征（HLHS）中，不同带环尺寸对分支肺动脉（PA）的能量损失以及冠脉血流的理论差异仍不清楚。我们的目的是建立一个计算流体动力学模型（CFD）来确定能量损失和肺循环与体循环的血流量。本研究针对三种不同的PA带环尺寸进行。
使用标准商业CFD软件Fluent和Gambit构建混合手术的三维计算机模型。计算机模型将双侧PA缩小至原分支肺动脉直径的25%（限制性）、50%（中等）和75%（宽松）。使用有限体积数值方法计算整个心脏几何结构中的速度和压力数据。同时测量每个模型的冠脉血流。计算壁面剪应力以及肺循环与体循环体积流量之比。利用超声心动图和基于导管的测量尺寸在固定点比较计算机模拟结果。
将PA带环限制在直径的25%时显示出最大的能量损失。25%带环模型的能量损失为收缩期16.76%和舒张期24.91%，而宽松带环分别为收缩期7.36%和舒张期17.90%。此外，限制性PA带环比宽松PA带环的冠脉血流更大（50.2对41.9毫升/分钟）。剪应力范围从限制性PA带环时的3.75帕斯卡到宽松带环时的2.84帕斯卡。直径50%的中等PA带环在收缩期1.46和舒张期0.66时达到Qp/Qs（最接近1），与宽松或限制性带环相比没有额外的能量损失。
CFD提供了一个独特的平台来模拟混合手术的压力、剪应力以及能量损失。50%的PA带环提供了平衡的肺循环和体循环，冠脉血流充足但没有额外的能量损失。
