Purpose

Variation in the rotational position of the aortic root relative to the left ventricle is present in normal trileaflet aortic valves. Its impact on the resulting fluid mechanics of blood flow in the thoracic aorta and structural mechanics in the aortic wall are unknown. We aimed to determine the regional hemodynamic and biomechanical differences in different rotational positions of the normal aortic root (clockwise, central, and counterclockwise positions).

Method

Cardiac magnetic resonance imaging (CMR) data was acquired from a normal pediatric patient. These were used for reconstruction of the aortic valve and thoracic aorta 3D model. Fluid–structure interaction (FSI) simulations were employed to study the influence of the root rotation with a central position as compared to observed extreme variations. Patient-specific phase-encoding CMR data were used to assess the validity of computed blood flow. The 3D FSI model was coupled with Windkessel boundary conditions that were tuned for physiological pressures. A grid velocity function was adopted for the valve motion during the systolic period.

Results

The largest wall shear stress level is detected in the clockwise positioned aortic root at the sinutubular junction. Two counter-rotating vortex cores are formed within the aortic root of both the central and extreme root configurations, however, in the clockwise root the vortex system becomes more symmetric. This also coincides with more entrainment of the valve jet and more turbulence production along the shear layer.

Conclusion

A clockwise rotational position of the aortic root imparts an increased wall shear stress at the sinutubular junction and proximal ascending aorta in comparison to other root rotation positions. This may pose increased risk for dilation of the sinutubular junction and ascending aorta in the patient with a clockwise positioned aortic root compared to other normal positional configurations.

中文翻译：

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正常变化的主动脉根旋转位置对胸主动脉血流动力学和组织生物力学的影响。

目的

在正常的三叶主动脉瓣中存在主动脉根相对于左心室的旋转位置的变化。它对由此产生的胸主动脉血流流体力学和主动脉壁结构力学的影响尚不清楚。我们的目的是确定正常主动脉根的不同旋转位置（顺时针，中心和逆时针位置）的区域血流动力学和生物力学差异。

方法

心脏磁共振成像（CMR）数据来自正常的儿科患者。这些用于重建主动脉瓣和胸主动脉3D模型。与观察到的极端变化相比，采用流固耦合（FSI）模拟来研究根部旋转对中心位置的影响。患者特定的阶段编码CMR数据用于评估计算的血流的有效性。3D FSI模型与针对生理压力进行调整的Windkessel边界条件结合在一起。在收缩期，气门运动采用了网格速度函数。

结果

在顺时针定位的主动脉根部，在窦管交界处检测到最大的壁切应力水平。在中心和极端根构型的主动脉根内都形成了两个反向旋转的涡流核，但是，在顺时针根中，涡流系统变得更加对称。这也与沿着剪切层的更多的气门射流夹带和更多的湍流产生相吻合。

结论

与其他根部旋转位置相比，主动脉根部的顺时针旋转位置会在窦管结和近端升主动脉处增加壁切应力。与其他正常的位置配置相比，这可能会使具有顺时针定位的主动脉根的患者扩张肾小管连接和升主动脉的风险增加。