Analysis of ischaemia in micro-myocardial region : evaluation of micro-deformation and image of NADH metabolic activity during ischaemia in a beating heart

心肌内由最小的小动脉支配的血管床的主要尺寸为几百毫米长。在这个大小水平上，冠状动脉血流分布的异质性是显著的。然而，目前尚不清楚冠状动脉血流分布的异质性是否与心脏跳动时心肌微变形有关。我们最近开发了一种微光标记植入麻醉开胸犬心脏表面的方法，利用我们新开发的高倍（×200）、高速（200帧/秒）CCD活体视频显微镜，直接观察到数百微米量级的心肌微变形。与此相比，更大尺度（毫米级样品尺寸）的变形也使用较低放大倍数的活体显微镜（×50）进行了分析。心肌收缩引起的大范围心肌变形较为均匀，但微范围变形具有异质性。此外，采用NADH荧光法对离体大鼠心脏氧代谢图像进行测量和分析。反映心肌氧代谢的异质心肌变形单位和斑块状NADH荧光单位的平均大小顺序相同。此外，在心肌壁切片上观察心肌内膜和心肌内膜之间的过渡性NADH活性。NADH荧光出现和消失的时间常数显示，心肌内膜比心肌外膜更容易缺氧。

The major size of a vascular bed that a minimum arteriole governs within myocardium is several hundreds mm long. At this level of size, the heterogeneity of coronary blood-flow distribution is remarkable. However, it is unknown whether the heterogeneity of a coronary blood-flow distribution relates to the myocardial micro-deformation in a beating heart.We have recently developed a micro-light markers implantation method onto the cardiac surface of anaesthetized open-chest dogs and directly observed the myocardial micro-deformation in hundreds micrometer order using our newly developed high-magnified(×200), high-speed(200 frames/sec)CCD intravaital videomicroscope. In comparison with this, deformation of larger scale(millimeter order sample size)was also analyzed using an intra-vital microscope with lower magnification(×50). Although the myocardial deformation by cardiac contraction in a macrodomain was comparatively uniform, deformation in a micro-domain showed heterogeneity.In addition, measurement and analysis of oxygen metabolism image of the isolated rat heart were done using a NADH fluorescence method. The average size of the heterogeneous myocardial deformation unit and patchy NADH fluorescence unit betraying mayocardial oxygen metabolism were in the same order. Furthermore, trasitional NADH activity at myocardial wall section was observed between epimyocardium and endomyocardium. The time constant of appearance and disappearance of NADH fluorescence revealed that endomyocardium is much more vulnerable to hypoxia than epimyocardium.