Section of Cardiovascular Medicine, Department of Medicine, Yale Translational Research Imaging Center, Yale University School of Medicine, New Haven, Connecticut, United States.
Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, Connecticut, United States.
Am J Physiol Heart Circ Physiol. 2023 Sep 1;325(3):H492-H509. doi: 10.1152/ajpheart.00735.2022. Epub 2023 Jul 7.
We present a detailed analysis of regional myocardial blood flow and work to better understand the effects of coronary stenoses and low-dose dobutamine stress. Our analysis is based on a unique open-chest model in anesthetized canines that features invasive hemodynamic monitoring, microsphere-based blood flow analysis, and an extensive three-dimensional (3-D) sonomicrometer array that provides multiaxial deformational assessments in the ischemic, border, and remote vascular territories. We use this model to construct regional pressure-strain loops for each territory and quantify the loop subcomponent areas that reflect myocardial work contributing to the ejection of blood and wasted work that does not. We demonstrate that reductions in coronary blood flow markedly alter the shapes and temporal relationships of pressure-strain loops, as well as the magnitudes of their total and subcomponent areas. Specifically, we show that moderate stenoses in the mid-left anterior descending coronary artery decrease regional midventricle myocardial work indices and substantially increase indices of wasted work. In the midventricle, these effects are most pronounced along the radial and longitudinal axes, with more modest effects along the circumferential axis. We further demonstrate that low-dose dobutamine can help to restore or even improve function, but often at the cost of increased wasted work. This detailed, multiaxial analysis provides unique insight into the physiology and mechanics of the heart in the presence of ischemia and low-dose dobutamine, with potential implications in many areas, including the detection and characterization of ischemic heart disease and the use of inotropic support for low cardiac output. Our unique experimental model assesses cardiac pressure-strain relationships along multiple axes in multiple regions. We demonstrate that moderate coronary stenoses decrease regional myocardial work and increase wasted work and that low-dose dobutamine can help to restore myocardial function, but often with further increases in wasted work. Our findings highlight the significant directional variation of cardiac mechanics and demonstrate potential advantages of pressure-strain analyses over traditional, purely deformational measures, especially in characterizing physiological changes related to dobutamine.
我们呈现了一份关于区域性心肌血流和工作的详细分析，旨在更好地理解冠状动脉狭窄和低剂量多巴酚丁胺应激的影响。我们的分析基于一个独特的麻醉犬开胸模型，该模型具有侵入性血流动力学监测、基于微球的血流分析以及广泛的三维（3-D）声速计阵列，可提供缺血、边界和远程血管区域的多轴向变形评估。我们使用该模型为每个区域构建区域性压力-应变环，并量化反映心肌工作以促进血液喷射和浪费工作的环子组件区域。我们表明，冠状动脉血流的减少显著改变了压力-应变环的形状和时间关系，以及它们的总子组件区域和子组件区域的大小。具体而言，我们表明，在左前降支中段的中度狭窄会降低区域性中心室心肌工作指数，并显著增加浪费工作的指数。在中心室，这些影响在径向和纵向轴上最为明显，在圆周轴上的影响较小。我们进一步表明，低剂量多巴酚丁胺可以帮助恢复甚至改善功能，但通常是以增加浪费工作为代价。这种详细的、多轴分析提供了对缺血和低剂量多巴酚丁胺存在时心脏生理学和力学的独特见解，在许多领域都有潜在的应用，包括缺血性心脏病的检测和特征描述以及使用正性肌力支持治疗低心输出量。我们独特的实验模型评估了多个区域和多个轴线上的心脏压力-应变关系。我们表明，中度冠状动脉狭窄会降低区域性心肌工作并增加浪费工作，而低剂量多巴酚丁胺可以帮助恢复心肌功能，但通常会进一步增加浪费工作。我们的发现突出了心脏力学的显著方向变化，并表明压力-应变分析相对于传统的、纯粹的变形测量具有潜在的优势，特别是在描述与多巴酚丁胺相关的生理变化方面。
