In vivo observation of coronary microcirculation using a needle-probe video-microscope with a CCD camera during cardiac surgery

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To evaluate the microcirculation of the human myocardium morphologically and functionally, we developed a portable needle-probe video-microscope with a charge coupled device (CCD) camera was applicable to the coronary microvessels during a cardiac surgery. First, using open-chest anesthetized pigs and dogs, we aimed to find technological hurdles for introducing the system during a surgery. Then, we developed several pieces of equipment to overcome the methodological problems. In brief, a sheathed needle-probe with a doughnut-shaped balloon was developed to avoid direct compression of the microvessels by the tip of the needle. To maintain a physiological condition of myocardial microvessels and the surrounding tissue during observation, a system consisting of a heat exchanger and a microtube was developed for flushing away the intervening blood between the tip of the needle and the myocardium. Using these devices, images of the myocardial microvessels of a beating heart could be obtained for a time which was long enough for imaging study. Furthermore, a holding device of the portable needle-probe video-microscope with a CCD camera was developed, which allowed an operator easy handling. This holding device contributed to shorten observation time. For the myocardial microvessels to be visualized without any special intravascular contrast medium, we employed a green (complimentary color of red) filter to accentuate the contrast between the images of the blood filled vessel and the surrounding tissue. Then, not only the coronary arterioles, but also coronary venules could be visualized. We confirmed that the portable needle-probe video-microscope with a CCD camera was able to visualize human coronary microvessels using all these supporting systems.We also evaluated the effects of nitroglycerin microvessels. The study showed that nitroglycerin dilates both subepicardial subendocardial arterioles. It was also found that nitroglycerin dilated coronary venules.