Institute of Diagnostic, Interventional and Pediatric Radiology, University Hospital Bern, Bern, Switzerland.
Department of Radiology, Medical Physics, University Hospital, Freiburg, Germany.
J Thorac Cardiovasc Surg. 2015 Jul;150(1):200-7. doi: 10.1016/j.jtcvs.2015.02.048. Epub 2015 Feb 28.
Left ventricular assist devices are an important treatment option for patients with heart failure alter the hemodynamics in the heart and great vessels. Because in vivo magnetic resonance studies of patients with ventricular assist devices are not possible, in vitro models represent an important tool to investigate flow alterations caused by these systems. By using an in vitro magnetic resonance-compatible model that mimics physiologic conditions as close as possible, this work investigated the flow characteristics using 4-dimensional flow-sensitive magnetic resonance imaging of a left ventricular assist device with outflow via the right subclavian artery as commonly used in cardiothoracic surgery in the recent past.
An in vitro model was developed consisting of an aorta with its supra-aortic branches connected to a left ventricular assist device simulating the pulsatile flow of the native failing heart. A second left ventricular assist device supplied the aorta with continuous flow via the right subclavian artery. Four-dimensional flow-sensitive magnetic resonance imaging was performed for different flow rates of the left ventricular assist device simulating the native heart and the left ventricular assist device providing the continuous flow. Flow characteristics were qualitatively and quantitatively evaluated in the entire vessel system.
Flow characteristics inside the aorta and its upper branching vessels revealed that the right subclavian artery and the right carotid artery were solely supported by the continuous-flow left ventricular assist device for all flow rates. The flow rates in the brain-supplying arteries are only marginally affected by different operating conditions. The qualitative analysis revealed only minor effects on the flow characteristics, such as weakly pronounced vortex flow caused by the retrograde flow via the brachiocephalic artery.
The results indicate that, despite the massive alterations in natural hemodynamics due to the retrograde flow via the right subclavian and brachiocephalic arteries, there are no drastic consequences on the flow in the brain-feeding arteries and the flow characteristics in the ascending and descending aortas. It may be beneficial to adjust the operating condition of the left ventricular assist device to the residual function of the failing heart.
左心室辅助装置是心力衰竭患者的重要治疗选择，可改变心脏和大血管中的血液动力学。由于无法对植入患者进行体内磁共振研究，因此体外模型是研究这些系统引起的血流变化的重要工具。通过使用尽可能模拟生理条件的体外磁共振兼容模型，本研究使用 4 维血流敏感磁共振成像技术对通过右锁骨下动脉流出的左心室辅助装置进行血流特性研究，这种装置在最近的心胸外科手术中被广泛应用。
开发了一个体外模型，该模型由主动脉及其上分支与模拟原生衰竭心脏脉动流的左心室辅助装置相连。第二个左心室辅助装置通过右锁骨下动脉为主动脉提供连续血流。对不同左心室辅助装置流量模拟原生心脏和提供连续血流的左心室辅助装置进行 4 维血流敏感磁共振成像。在整个血管系统中对血流特性进行定性和定量评估。
主动脉及其上分支血管内的血流特性表明，在所有流量下，右锁骨下动脉和右颈动脉仅由连续血流左心室辅助装置提供。大脑供血动脉的流量仅受不同工作条件的轻微影响。定性分析显示，仅对血流特性产生轻微影响，例如由于通过头臂动脉的逆行血流导致的微弱涡旋流。
尽管由于通过右锁骨下动脉和头臂动脉的逆行血流导致自然血液动力学发生巨大变化，但对大脑供血动脉的血流和升主动脉和降主动脉的血流特性没有严重影响。根据衰竭心脏的残余功能调整左心室辅助装置的工作条件可能是有益的。
