Department of Pathology, Toho University School of Medicine, Tokyo, Japan.
Circ J. 2011;75(7):1559-66. doi: 10.1253/circj.cj-10-1278. Epub 2011 Mar 31.
A myocardial bridge (MB), partially covering the coronary artery, is a congenital anatomical variant usually present in the left anterior descending coronary artery (LAD). MB causes coronary heart disease (CHD) by 2 distinct mechanisms influenced by the anatomical properties of the MB, such as its length, thickness, and location. One is direct MB compression of the LAD at cardiac systole, resulting in delayed arterial relaxation at diastole, reduced blood flow reserve, and decreased blood perfusion. The other is enhancement of coronary atherosclerosis causing stenosis of the LAD proximal to the MB, occurring because of endothelial injury arising from the abnormal hemodynamics provoked by retrograde blood flow up toward the left coronary ostium at cardiac systole. The magnitude of the effect of the 2 distinct mechanisms of the MB on LAD blood flow is prescribed by a common root of the MB-muscle mass volume generated by those properties. Furthermore, the anatomical properties of the MB are closely associated with the choice of treatment and therapeutic outcome in CHD patients having an MB. Thus, the anatomical properties of an MB should be considered in the diagnosis and management of CHD patients with this anomaly.
心肌桥（MB）是一种部分覆盖冠状动脉的先天性解剖变异，通常存在于左前降支冠状动脉（LAD）中。MB 通过 2 种不同的机制引起冠心病（CHD），这两种机制受 MB 的解剖学特性的影响，如 MB 的长度、厚度和位置。一种是 MB 在心脏收缩期直接压迫 LAD，导致舒张期动脉松弛延迟、血流储备减少和灌注减少。另一种是增强冠状动脉粥样硬化，导致 MB 近端的 LAD 狭窄，这是由于心脏收缩时逆向血流向上流向左冠状动脉口引起的异常血流动力学导致内皮损伤所致。MB 对 LAD 血流的 2 种不同机制的影响程度由这些特性产生的 MB-肌肉质量体积的共同根源决定。此外，MB 的解剖学特性与患有 MB 的 CHD 患者的治疗选择和治疗效果密切相关。因此，在诊断和管理患有这种异常的 CHD 患者时，应考虑 MB 的解剖学特性。
