Institute for Surgical Research, Oslo University Hospital , Oslo , Norway.
Department of Cardiology, Oslo University Hospital , Oslo , Norway.
J Appl Physiol (1985). 2018 Nov 1;125(5):1482-1489. doi: 10.1152/japplphysiol.00255.2018. Epub 2018 Sep 6.
Atrial switch operation in patients with transposition of the great arteries (TGA) leads to leftward shift and changes the geometry of the interventricular septum. By including the implications of regional work and septal curvature, this study investigates if changes in septal function and geometry contribute to reduced function of the systemic right ventricle (RV) in adult TGA patients. Regional myocardial work estimation has been possible by applying a recently developed method for noninvasive work calculation based on echocardiography. In 14 TGA patients (32 ± 6 yr, means ± SD) and 14 healthy controls, systemic ventricular systolic strains were measured by speckle tracking echocardiography and regional work was calculated by pressure-strain analysis. In TGA patients, septal longitudinal strain was reduced to -14 ± 2 vs. -20 ± 2% in controls ( P < 0.01) and septal work was reduced from 2,046 ± 318 to 1,146 ± 260 mmHg·% ( P < 0.01). Septal circumferential strain measured in a subgroup of patients was reduced to -11 ± 3 vs. -27 ± 3% in controls ( P < 0.01), and a reduction of septal work (540 ± 273 vs. 2,663 ± 459 mmHg·%) was seen ( P < 0.01). These reductions were in part attributed to elevated afterload due to increased radius of curvature of the leftward shifted septum. To conclude, in this mechanistic study we demonstrate that septal dysfunction contributes to failure of the systemic RV after atrial switch in TGA patients. This is potentially a long-term response to increased afterload due to a flatter septum and suggests that medical therapy that counteracts septal flattening may improve function of the systemic RV. NEW & NOTEWORTHY We have demonstrated that transposition of the great arteries patients with systemic right ventricles (RVs) have reduced function of the interventricular septum (IVS). Since the IVS is constructed to eject into the systemic circulation, it may seem unexpected that it does not maintain function when being part of the systemic RV. By applying the principles of regional work, wall tension, and geometry, we have identified unfavorable working conditions for the IVS when the RV adapts to systemic pressures.
大动脉转位（TGA）患者的房间隔切换操作导致左移并改变了室间隔的几何形状。通过包括区域性工作和隔曲率的影响，本研究调查了室间隔功能和几何形状的变化是否导致 TGA 成年患者的系统性右心室（RV）功能降低。通过应用最近开发的基于超声心动图的无创性工作计算方法，已经可以估计区域性心肌工作。在 14 名 TGA 患者（32 ± 6 岁，平均值 ± 标准差）和 14 名健康对照者中，通过斑点追踪超声心动图测量了系统性心室收缩应变，并通过压力-应变分析计算了区域性工作。在 TGA 患者中，室间隔纵向应变降低至 -14 ± 2%，而对照组为 -20 ± 2%（P < 0.01），室间隔工作从 2046 ± 318mmHg·%降低至 1146 ± 260mmHg·%（P < 0.01）。在患者的一个亚组中测量的室间隔周向应变降低至 -11 ± 3%，而对照组为 -27 ± 3%（P < 0.01），并且观察到室间隔工作的降低（540 ± 273 对 2663 ± 459mmHg·%）（P < 0.01）。这些降低部分归因于由于向左移位的室间隔曲率半径增加而导致的后负荷升高。总之，在这项机制研究中，我们证明了 TGA 患者房间隔切换后室间隔功能障碍导致系统性 RV 衰竭。这可能是由于室间隔变平导致的长期后负荷增加的反应，并表明对抗室间隔变平的药物治疗可能改善系统性 RV 的功能。
新内容和值得注意的地方
我们已经证明，具有系统性右心室（RV）的大动脉转位（TGA）患者的室间隔（IVS）功能降低。由于 IVS 的设计目的是向体循环喷射，因此当它成为系统性 RV 的一部分时，它不能维持功能似乎出人意料。通过应用区域性工作、壁张力和几何形状的原理，我们已经确定了当 RV 适应体循环压力时，IVS 的不利工作条件。
