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的最主要部位是小动脉，因此在微观水平上评估冠状动脉循环对于了解冠状动脉血管调节功能是必不可少的。在这项研究中，我们应用了一种新开发的一氧化氮（NO）微传感器来测量血管组织一氧化氮的浓度，一氧化氮在局部心肌血流调节中起着重要作用。此外，我们通过数字x线摄影结合分子沉积技术可视化了层内心肌灌注的空间格局。心肌灌注模式的分层结构特征反映在心肌灌注模式中，因此对冠状动脉的血管调节提供了有价值的信息。实验结果总结如下：将No传感器插入离体犬股动脉的血管介质中，用Krebs-Henseleit溶液灌注。血管介质中的NO浓度随灌注流速（血管壁上的流动剪切应力）和NO合成酶底物l -精氨酸的添加而线性增加。通过灌注含有NO合成酶抑制剂N^< ω >-硝基- l -精氨酸的溶液，可以减弱NO的产生，即测量电流。实验结果表明，新型一氧化氮传感器对血管介质中一氧化氮的选择性测量具有满意的性能。在高氧消耗或低氧供应状态下，微区域心肌血流更加均匀和连续。左心室局部血流相关性存在跨壁差异，这可能是由于心内膜下的O_2消耗较高所致。由于在缺氧时心膜下的区域血流相关性增加到与在心内膜下观察到的相似的水平，因此在正常缺氧时心膜下允许不均匀的血流模式，但在缺氧时与心内膜下相比不再允许。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