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

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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.