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

本项目旨在开发一种高速CCD显微镜系统，用于心脏缺血风险最大的心内膜下心肌层微血管行为和微循环血流动力学的评价研究。我们首先研制了高速CCD显微镜，并对其性能进行了评价。该系统由针探头、相机本体、缓冲存储器和盒式录像机组成。每隔5 ms（200张/s）将血管图像通过针尖探头聚焦到专用CCD上存储在数字存储器中。针尖处的视野大小为1.0*0.8 mm^2，空间分辨率约为2mum。CCD系统使用光学发光微球来显示微血管中的血流速度。该系统采用直径为3 μ m、比重为1.3的微球和缺血心肌的NADH荧光图像，成功地实现了心肌毛细血管内血流的可视化。主要结果如下：1)与其他器官毛细血管不同，微球在心脏周期内的速度模式是动态变化的，其速度波形表现为完全舒张期血流和双峰收缩期逆血流。2)随着灌注压的降低，心下和心内膜下小动脉出现反应性扩张。3)短暂性冠状动脉闭塞时，心肌缺血区域NADH荧光测量显示出空间微观异质性，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.