Evaluation of Coronary Vasoregulation Through Controlling Regional Myocardial Flow

心肌灌注的内在模式是由冠状动脉血管张力决定的。由于冠状动脉血管张力最主要的部位是小动脉，因此在显微镜水平上评价冠状动脉循环对于了解冠状动脉的血管调节功能是必不可少的。在这项研究中，我们应用一种新的一氧化氮(NO)微型传感器来测量在局部心肌血流调节中起重要作用的血管组织中的NO浓度。此外，我们通过数字摄影结合分子沉积技术可视化了层内心肌灌注的空间模式。心肌灌注模式反映了心肌组织的层次结构特征，因此对心肌灌注模式的分析对冠状动脉血管调节具有重要意义。实验结果如下：将NO传感器植入犬离体股动脉的血管中膜，灌流…更有Krebs-Henseleit解决方案。血管中NO浓度与灌流速度(血管壁上的血流剪切力)以及给予一氧化氮合酶底物L-精氨酸呈线性增加。通过灌流含有一氧化氮合酶抑制剂-硝基-L-精氨酸的溶液来减弱一氧化氮的产生，即测量的电流。结果表明，这种新型的NO传感器在选择性测量血管介质中的NO方面具有令人满意的性能，在高耗氧或低供氧状态下，微区域心肌血流更加均匀和连续。左室心肌局部血流相关性存在跨壁差异，这可能与心内膜下心肌耗氧量较高有关。由于低氧时心外膜下的局部血流相关性增加到与心内膜下相似的水平，因此常氧下心外膜允许不同的血流模式，但与心内膜下相比，低氧时心外膜下不再允许不同的血流模式。较少

The intrinsic pattern of myocardial perfusion is determined by coronary vascular tone. Since the most principal sites of coronary vascular tone are the arterioles, the evaluation of coronary circulation on a microscopic level is indispensable to understand the coronary vasoregulatory function. In this study, we applied a newly developed nitric oxide (NO) microsensor to measure the concentration of vascular tissue NO,which plays an essential role in regional myocardial flow regulation. Furthermore, we visualized the spatial pattern of within-layr myocardial perfusion by digital-radiography combined with a molecular deposition technique. The analysis of myocardial perfusion pattern gives valuable information on the coronary vasoregulation because its characteristics of hierarchical structure are reflected in myocardial perfusion pattern. The experimental results were summarized as follows.The No sensor was inserted into the vascular media of the isolated canine femoral artery, perfused w … More ith a Krebs-Henseleit solution. NO concentration in the vascular media increased linearly with perfusion flow rate (flow shear stress on the vascular wall) and also with administration of a substrate of NO synthase, L-arginine. NO production, i. e., measured current was attenuated by perfusing a solution containing an inhibitor of NO synthase, N^<omega>-nitro-L-arginine. It is thus shown that the new NO sensor has satisfactory performance for a selective measurement of NO in the vascular media.Microregional myocardial flows are more uniform and continuous at high O_2 consuming or low O_2 supply states. There were transmural differences in a regional flow correlation in the left ventricular myocardium, which may be due to the higher O_2 consumption in the subendocardium. Since the regional flow correlation in the subepicardium was increased to a similar level observed in the subendocardium during hypoxia, the subepicardium will allow heterogeneous flow patterns in normoxia, but not anymore in hypoxia in comparison with the subendocardium. Less