Analysis on local blood flow, metabolic NADH distribution and micro-mechanical dysfunction during ischaemia of coronary micro-circulation

通过直接评价冠状动脉微循环NADH荧光图像和分子血流示踪剂测量毛细血管血流分布，分析心肌微循环缺血和线粒体功能障碍的空间异质性。NADH荧光成像系统采用一台40万像素的CCD相机来观测激发紫外线的发射荧光(420-570 nm)。该系统的优点是易于对NADH动力学进行荧光观测，并具有高空间分辨率和高时间分辨率。血流分布成像采用分子血流示踪剂(3 H-去甲基米帕明)，空间分辨率为100 mm。实验采用60s低氧灌流法制备大鼠离体心。在实验过程中，记录心脏的NADH荧光并应用分子血流示踪剂。本研究的结果是：缺氧灌流后即刻，NADH强度与线粒体内NADH含量成正比增加，并出现高信号和低信号混合的斑片状(数百微米大小)。分子示踪剂同时测量的血流分布也显示出空间不均一性，每个斑点的大小在几百微米量级，这与NADH荧光观察到的斑块面积几乎相同。此外，在100微米大小的心肌微循环水平上测量的微应变也显示出心脏表面的不均一性。综上所述，血流、代谢紊乱和微应变之间存在分布关系。提示异质性心肌缺血区与血液分布和线粒体代谢紊乱密切相关。

We analyzed ischaemia of myocardial micro-circulation and spatial heterogeneity of mitochondrial dysfunction by direct evaluation of NADH fluorescent image in coronary micro-circulation and measurement of capillary blood flow distribution using molecular blood flow tracer. NADH fluorescence imaging system has a CCD camera with 400 thousand pixels to observe the emission fluorescence (420 - 570 nm) against ex-citation ultraviolet ray. The advantages of this system are easy observation by fluorescence for NADH dynamics and high spatial resolution with high time resolution. Blood flow distribution imaging was achieved with molecular blood flow tracer (3H-Desmethylimipramine) with 100 mm spatial resolution. Experiment was performed by 60 seconds hypoxic perfusion in isolated rat heart perfusion preparation. During the experiment, NADH fluorescence from the heart was recorded and molecular blood flow tracers were administered. The findings of the present study were; NADH intensity increased in proportion to the intra-mitochondrial NADH amount immediately after hypoxic perfusion and patchy patterns appeared with mixture of high and low intensity of NADH (several hundreds microns in size). Simultaneous measurement of blood flow distribution by molecular tracers also showed spatial heterogeneity and the size of each spotty area was in order of several hundred microns, which was almost identical with the patch area observed by NADH fluorescence. Furthermore, micro-strain measured at the level of myocardial micro-circulation with the size of a hundred microns also showed heterogeneity on the surface of a heart. Taken together, there is a relationship in distribution among blood flow, metabolic dysfunction and micro-strain. This indicates that hetrogenous myocardial ischaemic area is closely related with blood distribution and mitochondrial metabolic dysfunction.