心肌橋(myocardial bridge; 簡稱MB) 是指冠狀動脈或其分支被心肌纖維組織所覆蓋，而覆蓋在上的心肌纖維則稱為心肌橋。心肌橋大部分發生在左前降枝冠狀動脈(LAD) 的中段部位，少數發生在其他的冠狀動脈。發生心肌橋的血管通常不易發生動脈粥狀硬化(atherosclerosis)，而鄰近心肌橋近端的冠狀動脈內膜則易產生粥狀硬化。本次研究的目的是利用64 列多排偵檢器電腦斷層掃描儀(64MDCT) 來評估左前降枝冠狀動脈心肌橋的發生率、位置、深度、長度以及鄰近心肌橋前端的血管有無動脈粥狀硬化的情形。研究對象包含358 位年齡介於10 歲~89 歲之間的受檢者，其中男性佔112位，女性為246 位。研究結果顯示MB發生率為22.4%，男性的發生率23.6%(58/246)，而女性則為19.6%(22/112)。在80 例MB 中，有41 (51%) 例在MB 前端的血管發現動脈粥狀硬化，MB 處的血管則沒有動脈粥狀硬化。冠心病家族史、高血壓、高血脂、糖尿病及抽煙史與MB 的發生無關聯性(p > 0.05)。MDCT 針對MB 的診斷率高又能提供精確的冠狀動脈解剖構造及週邊心肌的相對位置，故MDCT 可提供在活體試驗中(in vivo)MB 的真正發生率。

Background and Purpose: A myocardial bridge (MB) is a congenital coronary anomaly resulting in systolic narrowing of the coronary artery. The purposes of this study were to assess the prevalence rate ofMB and evaluate the relation between MBs and atherosclerosis proximal to the bridges in the left anterior descending coronary artery (LAD) using 64 multiple detector row computed tomography (MDCT). Materials and Methods: In total, 358 subjects either with or without cardiac symptoms who underwent CT coronary angiography were included in the study. The prevalence, thickness, length, and location of the MBs and atherosclerosis proximal to the bridge were evaluated. Results:We found that 22.4% (80/358) of subjects had anMB in the LAD. Themid-LAD was the most common site (17.4%). Forty-one subjects had atherosclerosis proximal to the MB. No atherosclerosis was found in the bridged segment. The mean thickness and length of bridge were 1.2 ± 1.1 and 13.7 ± 6.9 mm, respectively. The presence of atherosclerosis in the LAD segment proximal to the MB and the severity of atherosclerosis in these segments were not related to the length or depth of the bridge. Conclusions: The prevalence rate ofMB in our groupwas higher (22.4%) than those of previous angiographic reports (0.5%~2.5%). Segments proximal to the myocardial bridge had a higher frequency of atherosclerosis, whereas the MB segment was spared. MDCT is a reliable, less-invasive technique for diagnosing MBs and evaluating the anatomical properties ofMBs.