PURPOSE: This study is to determine the feasibility and usefulness of MSCT for evaluation of myocardial bridging. METHODS: Ten volunteers (age; 44-67; mean 55, men 8, women 2) without ischemic heart disease and 34 consecutive patients (age; 28-79; mean 56, men 20, women 14) with ischemic chest pain underwent CT coronary angiography (Sensation 16, Siemens, Germany). CT protocol included coronary calcium scoring and angiography. Left anterior descending artery (LAD) from proximal to distal was scrutinized for presence of myocardial bridging with multiplanar reformatted images. Myocardial bridge was determined by demonstration of tunneled segment dip into myocardium. The location, length, depth, area were assessed. Invasive coronary arteriography was performed in 12 patients with stenosis that was determined by CT. RESULTS: Twelve tunneled segments in LAD was detected in two volunteers (20%) (n=2) and 8 patients (23%) (n=10). Nine were located in middle LAD (2 in volunteers, 7 in patients) and 3 in distal LAD (in patients). The length measured 4 to 36 mm (mean 17 mm). The greater depth measured 0 to 4.5 mm (mean 1.2 mm). The cross-sectional areas of the narrowest points of tunneled segments were measured 39% smaller than those of the just proximal segments (p=0.001) and 10% smaller than those of just distal segments to the tunneled segments (p=0.016). In visual assessment, 8 tunneled segments showed mild narrowing of diameter and the rest showed no definite narrowing. Calcification in LAD was detected in 1 (50%) volunteer and 4 (50%) patients with myocardial bridge but not in tunneled segments themselves. Significant stenosis was detected in proximal LAD of two patients and mild stenosis in one patient which were confirmed by invasive coronary arteriography. Five patients showed isolated myocardial bridge in LAD without stenosis of coronary arteries having diameter more than 2mm by CT. CONCLUSIONS: MSCT is able to directly visualize tunneled segments running through myocardium with myocardial fibers crossing over them. Further study with functional evaluation in a large population is suggested to elucidate clinical significance of myocardial bridging detected by MSCT.