Department of Cardiothoracic Surgery (F.M.R., M.G.H.).
Leiden University Medical Center, The Netherlands. Department of Biomechanical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands (J.J.W.).
Circulation. 2018 May 29;137(22):2393-2407. doi: 10.1161/CIRCULATIONAHA.117.033359.
Visualization and quantification of the adverse effects of distorted blood flow are important emerging fields in cardiology. Abnormal blood flow patterns can be seen in various cardiovascular diseases and are associated with increased energy loss. These adverse energetics can be measured and quantified using 3-dimensional blood flow data, derived from computational fluid dynamics and 4-dimensional flow magnetic resonance imaging, and provide new, promising hemodynamic markers. In patients with palliated single-ventricular heart defects, the Fontan circulation passively directs systemic venous return to the pulmonary circulation in the absence of a functional subpulmonary ventricle. Therefore, the Fontan circulation is highly dependent on favorable flow and energetics, and minimal energy loss is of great importance. A focus on reducing energy loss led to the introduction of the total cavopulmonary connection (TCPC) as an alternative to the classical Fontan connection. Subsequently, many studies have investigated energy loss in the TCPC, and energy-saving geometric factors have been implemented in clinical care. Great advances have been made in computational fluid dynamics modeling and can now be done in 3-dimensional patient-specific models with increasingly accurate boundary conditions. Furthermore, the implementation of 4-dimensional flow magnetic resonance imaging is promising and can be of complementary value to these models. Recently, correlations between energy loss in the TCPC and cardiac parameters and exercise intolerance have been reported. Furthermore, efficiency of blood flow through the TCPC is highly variable, and inefficient blood flow is of clinical importance by reducing cardiac output and increasing central venous pressure, thereby increasing the risk of experiencing the well-known Fontan complications. Energy loss in the TCPC will be an important new hemodynamic parameter in addition to other well-known risk factors such as pulmonary vascular resistance and can possibly be improved by patient-specific surgical design. This article describes the theoretical background of mechanical energy of blood flow in the cardiovascular system and the methods of calculating energy loss, and it gives an overview of geometric factors associated with energy efficiency in the TCPC and its implications on clinical outcome. Furthermore, the role of 4-dimensional flow magnetic resonance imaging and areas of future research are discussed.
血流变形的不良影响的可视化和量化是心脏病学中新兴的重要领域。各种心血管疾病中可见异常的血流模式，并与能量损失增加有关。这些不良能量可以使用来自计算流体动力学和 4 维血流磁共振成像的 3 维血流数据进行测量和量化，并提供新的、有前途的血流动力学标志物。在姑息性单心室心脏缺陷患者中，Fontan 循环在没有功能性亚肺心室的情况下被动地将体循环静脉回流引导至肺循环。因此，Fontan 循环高度依赖于有利的血流和能量，最小的能量损失非常重要。关注减少能量损失导致引入全腔静脉肺动脉连接（TCPC）作为经典 Fontan 连接的替代方案。随后，许多研究调查了 TCPC 中的能量损失，并在临床护理中实施了节能的几何因素。在计算流体动力学建模方面取得了巨大进展，现在可以在 3 维患者特异性模型中进行，边界条件越来越准确。此外，4 维血流磁共振成像的实施具有很大的潜力，并且可以对这些模型具有补充价值。最近，已经报道了 TCPC 中的能量损失与心脏参数和运动不耐受之间的相关性。此外，TCPC 中血流的效率变化很大，低效的血流通过降低心输出量和增加中心静脉压而具有临床重要性，从而增加了经历众所周知的 Fontan 并发症的风险。除了肺血管阻力等其他已知危险因素外，TCPC 中的能量损失将成为一个重要的新血流动力学参数，并可能通过患者特异性手术设计得到改善。本文描述了心血管系统中血流机械能的理论背景和计算能量损失的方法，并概述了与 TCPC 中能量效率相关的几何因素及其对临床结果的影响。此外，还讨论了 4 维血流磁共振成像的作用和未来研究领域。
