Molecular and Clinical Pathological Studies on Atherosclerosis Suppression in the Coronary Artery by Myocardial Bridge.

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The mechanism of atherosclerosis suppression by myocardial bridge(MB) consisting of myocardial tissue which covers a part of the LAD running in the epicardial adipose tissue has been explored from the viewpoints of vascular constriction proteins and coagulation/fibrinolysis proteins in the vascular endothelium and smooth muscle cells altering their expression in accordance with shear stress against the LAD vascular wall.. In addition, the effects of anatomical properties of MB, such as the location of MB within the LAD as well as the length and thickness of MB, on the LAD vascular wall were histomorphometrically investigated.Results1. Intimal thickness beneath MB was significantly lower than that proximal and distal to MB. Furthermore, The expression of e-nitrogen oxide synthase, endothelin-l.angiotensin converting enzyme in endomelium, smooth muscle cells or intimal stroma in the bridged segment was significantly lower there than that proximal and distal to MB.2. In addition to the results of 1, the expression of coagulation/fibrinolysis proteins, such as tissue factor, plasminogen activator-1, tissue plasminogen activator in endothelium, smooth muscle cells or intimal stroma in the bridged segment was also lower significantly than that proximal and distal to MB. The findings of 1 and 2 indicate that the LAD intima beneath the segment of MB was exempt from atherosclerosis development due to the lowering expression of those molecules at the bridged segment.3. By nalysis on the relationship between the anatomical properties, such as the location of MB within the LAD as well as the kength and thickness of MB, and intimal thickness of the LAD, the longer and thicker the anatomical properties of MB were, the greater the effect of atherosclerosis suppression by MB was. The results of 1, 2 and 3 indirectly illustrate that the vascular wall of MB is stressed with higher shear stress than the LAD segments proximal and distal to MB.