Molecular Pathology on Atherosclerosis Suppression in the Left Anterior Descending Coronary Artery due to Shear Stress under Myocardial Bridge

对200例有心肌桥的LAD和100例无心肌桥的LAD进行了组织形态计量学研究。所有受试者均以5 mm为间隔进行横断面扫描。光镜下进行HE和EVG染色后，进行组织形态计量学研究。在计算机辅助系统上测量左前降支MB入口位置、长度和心肌厚度的解剖学性质。在MB作用下，冠状动脉粥样硬化程度始终受到抑制。心肌MB厚度与MB长度呈正相关。MB节段以下心肌MB厚度对动脉粥样硬化的抑制作用显著。免疫组织化学：利用组织因子、组织型纤溶酶原激活物和纤溶酶原激活物抑制物1的抗体，对上述标本进行免疫组织化学染色。前两者的凝血因子下调，后者的纤溶因子在冠脉节段上调。这些改变是由于横跨MB的剪应力变化引起的，最终导致LAD MB节段下的动脉粥样硬化。

I.Histomorphometric StudyIt is carried on the 200 consecutive LADs having myocardial bridge(MB) and 100 LADs having no MB. All the LADs were cross-psectioned with the intervals of 5 mm. After HE and EVG stainings for light microscopy, they were subjected to histomorphometric study. The anatomic properties of location of entrance, length and myocardial thickness of MB in the LAD were measured by the computer assisted system. Under MB, the extent of coronary atherosclerosis was always suppressed,. The myocardial thickness of MB was innassociation with MB length. The myocardial thickness of MB had significant effect on atherosclerosis suppression under MB segment. The anatomical properties of MB played significant role on atherosclerosis suppression.II.ImmunohistochemistryUsing the antibodies of tissue factor, tissue plasminogen activator and plasminogen-activator inhibitor 1, immunohistochemistry was carried out on the above specimens. Blood coiagulative factors of the former two were down-regulated and fibrinolysis factor of the latter one was up-regulated in the coronary segment under MB. These changes were rcaused by the changes of shear stress across MB, and finally resulted in atherosclerosis under MB segment in the LAD.