Analysis of hemodynamics in intramyocardial microcirculation using needle-probe fluorescent intravital microscope

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To visualize the subendocardial arteriolar blood velocity, we have developed a high-speed CCD microscope. The vascular images, focused on the special CCD through a needle-probe, were stored on a digital memory every 5 ms (200images/s). A size of visual field is 1*0.8mm^2, and a spatial resolution is less than 4mum. The blood flow velocities in the microvessels were visualized with optically shinning microspheres (MS) as optical marker. The optical marker (5-15 mumphi) was prepared by polymerization of stirene monomer with homogeneously distributed fine particles of heavy elements (0.2 mumphi). Velocities of MS in the subepicardial and subendocardial arteriole were calculated by the movement distance of MS every 5 ms. To visualize flow on the monitor, the MS was injected into the left anterior descending coronary artery. The MS images of first-pass were recorded on a video-cassette recorder. Positions of MS in the microvessels were measured using a computer system. Velocities of MS in the subendocardial arteriole were calculated by frame-to-frame analysis from the movement distance of MS.In endocardial arterioles, fast forward flow was observed during diastole, while there was retrograde flow with two peaks during systole. In epicardial arterioles, fast forward flow was observed during diastole, similar to the subendocardial blood flow. However, a plenty of forward flow was also observed in systolic phase. The novel achievement in this study is the direct observation of subendocardial blood flow in arterioles during a cardiac cycles at highly temporal resolution.