Evaluation of Subendocardial Microcirculatory Hemodynamics by High-Speed Needle-Probe CCD Microscope

本课题的目的是研制一种高速CCD显微系统，用于评价心肌缺血风险最大的内膜下心肌层的微血管行为和微循环血流动力学的研究。我们首先开发了一个高速CCD显微镜，并评估其性能。该系统由探针、摄象机、缓冲存储器和录像机组成。通过针探头聚焦在专用CCD上的血管图像每5 ms（200幅图像/s）存储在数字存储器中。针尖处的视场大小为1.0 × 0.8 mm^2，空间分辨率约为2 μ m。微血管中的血流速度通过使用光学发光微球的CCD系统可视化。该系统利用微球（直径3 μ m，比重1.3）和缺血心肌的NADH荧光图像，成功地显示了心肌毛细血管中的血流。主要结果如下：1）微球在一个心动周期内的流速模式是动态变化的，与其他器官的毛细血管不同，微球的流速波形为舒张期流速，收缩期流速为双峰反向流速。2)心外膜下和心内膜下小动脉对灌注压的降低有反应性扩张。3)在短暂的冠状动脉闭塞，缺血心肌区域评估的NADH荧光显示空间的微观异质性和每个缺血区域的大小约为几百微米。

Goal of this project was to develop a high-speed CCD microscopy system which can be applied to the studies on the evaluation of microvascular behavior and microcirculatory hemodynamics in the subendocardial myocardial layrs which is at greatest risk of ischemia in the heart. We first developed a high speed CCD microscope and evaluated its performance. This system consists of a needle probe, a camera body, a buffer memory and a videocassette recorder. The vascular images focused on the special CCD through a needle-probe are stored on a digital memory every 5 ms (200images/s). A size of visual field at the needle tip is 1.0*0.8 mm^2 and a spatial resolution is about 2mum. The blood flow velocities in the microvessels were visualized by the CCD system using an optically shinning microsphere. This new system successfully visualized flow in myocardial capillary vessels by using microspheres (diameter : 3mum, specific gravity : 1.3) and NADH fluorescence image from the ischemic myocardium. Major findings are as followings : 1) The velocity pattern of microspheres changed dynamically during a cardiac cycle unlike in the capillary vessels of other organs : the velocity waveform was characterized by exclusively diastolic flow with two-peak systolic reverse flow. 2) In response to the decrease in perfusion pressure, subepicardial-and subendocardial arterioles showed reactive dilations. 3) In response to a transient coronary occlusion, ischemic myocardial region as evaluated by the NADH fluorescence showed spatial microheterogeneity and the size of each ischemic region was about several hundred micron meters.