Dwyer Harry A, Matthews Peter B, Azadani Ali, Ge Liang, Guy T Sloane, Tseng Elaine E
Department of Mechanical and Aeronautic Engineering, University of California at Davis, Davis, CA, USA.
J Thorac Cardiovasc Surg. 2009 Nov;138(5):1227-33. doi: 10.1016/j.jtcvs.2009.02.057. Epub 2009 Sep 13.
Transcatheter aortic valves have been successfully implanted into the calcified leaflets of patients with severe aortic stenosis. However, their stability in patients with noncalcified aortic insufficiency is unknown. Similar to thoracic and abdominal aortic stent grafts, transcatheter aortic valves are subjected to antegrade ejection forces during systole. However, retrograde migration forces into the left ventricle are also generated by the diastolic pressure gradient across the closed valve. It has been suggested that leaflet calcification anchors the prosthesis, and measurements of migration forces should be considered before clinical trials in noncalcified aortic insufficiency. The objective of this study was to use computational fluid dynamics simulations to quantify forces that could potentially dislodge the prosthesis.
A computational fluid dynamics model was developed to simulate systolic flow through a geometric mesh of the aortic root and transcatheter aortic valves. Hemodynamic measurements were made at discrete moments during ejection. Unsteady control volume analysis was used for calculations of force on the mesh.
Results of the simulation indicate that a total force of 0.602 N acts on the transcatheter aortic valves during systole, 99% of which is in the direction of axial flow. The largest contributor to force was the dynamic pressure gradient through the transcatheter aortic valves. This antegrade force is approximately 10 times smaller than the retrograde force (6.01 N) on the closed valve during diastole.
Our model simulated systolic flow through a transcatheter aortic valve and demonstrated migration into the left ventricle to be of greater concern than antegrade ejection.
经导管主动脉瓣已成功植入严重主动脉瓣狭窄患者的钙化瓣叶。然而，其在非钙化主动脉瓣关闭不全患者中的稳定性尚不清楚。与胸主动脉和腹主动脉支架移植物类似，经导管主动脉瓣在收缩期会受到顺行射血力。然而，跨关闭瓣膜的舒张压梯度在舒张期也会产生逆行向左心室的迁移力。有人提出瓣叶钙化可固定假体，在非钙化主动脉瓣关闭不全的临床试验前应考虑测量迁移力。本研究的目的是使用计算流体动力学模拟来量化可能使假体移位的力。
建立计算流体动力学模型，以模拟通过主动脉根部和经导管主动脉瓣的几何网格的收缩期血流。在射血过程中的离散时刻进行血流动力学测量。使用非定常控制体积分析来计算网格上的力。
模拟结果表明，收缩期作用于经导管主动脉瓣的总力为0.602N，其中99%沿轴向血流方向。对力贡献最大的是通过经导管主动脉瓣的动压梯度。该顺行力比舒张期作用于关闭瓣膜的逆行力（6.01N）小约10倍。
我们的模型模拟了通过经导管主动脉瓣的收缩期血流，并表明向左心室的迁移比顺行射血更值得关注。
