Analysis of Coronary Slosh Phenomenon by Needle-probe CCD Microscope and Molecular Blood Flow Tracer

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It is well known as an important pathophysiological feature of the ischemic heart disease that subendocardium is more susceptible to ischemia than subepicardium. However, the mechanism which is responsible for the subendocardial vulnerability to ischemia is not fully understood yet. We considered that coronary slosh phenomenon, i.e., the to-and-fro movement of the blood between proximal portion of the coronary artery and intramyocardial arterioles would at least partially be responsible to the subendocardial vulnerability to ischemia. To understand the nature of the microvascular behavior in relation to the coronary slosh phenomenon, we measured the diameters of the myocardial microvessels of the beating canine heart during cardiac cycle by introducing a needleprobe videomicroscope with a CCD camera. We also aimed to understand its relation to the spatial distribution of the myocardial blood flow by introducing a novel molecular blood flow tracer analysis, and to evaluate the influence … More of alpha-adrenergic activation to the coronary slosh phenomenon.The coronary arteriolar diameter of epicardium increased during systole, whereas those of endocardium and midmyocardium decreased by about 20%. These results indicate that the compression of the intramyocardial arterioles vessels due to myocardial contraction, which is supposed to be greater in the subendocardium than in the subepicardium, would be the mechanical cause of the coronary slosh phenomenon. Analysis of the myocardial blood flow distribution showed that during physiological condition, regulation unit of myocardial microcirculation would be 500-600 mum and the correlation between adjacent regional flows of the deep myocardial layr is larger than that of superficial myocardial layr.Alpha-adrenergic activation reduced the coronary slosh phenomenon, suggesting that the alpha-adrenergic activity plays a role in distributing the blood favorably toward the subendocardium, where is at greatest risk of ischemia on increased alpha-adrenergic drive during exercise or mental stress. Less