Myocardial bridging of the left anterior descending coronary artery: depiction rate and morphologic features by dual-source CT coronary angiography

Abstract

Objective: To evaluate the depiction rate and morphologic features of myocardial bridging (MB) of the left anterior descending coronary artery (LAD) using dual-source CT (DSCT).

Materials and methods: CT scans from a total of 1,353 patients who underwent DSCT were reviewed retrospectively for LAD-MB. Seventy-eight patients were excluded due to poor image quality or poor enhancement of the coronary artery. The length and depth of the MB were analyzed and classified as superficial or deep with respect to the depth (<or= 1 or > 1 mm) of the LAD tunneled segment. Superficial MB was subdivided into complete or incomplete types according to full or partial encasement of the myocardium.

Results: Of the 1,275 patients included in this study, 557 cases of MB were found from 536 patients (42%). Superficial MB was observed in 368 of 557 (66%) cases, and deep MB was seen in 189 of 557 (34%) cases. Superficial MB showed 2 types: complete (128 of 368, 35%) and incomplete (240 of 368, 65%). The mean length of a tunneled segment for superficial MB was 16.4 +/- 8.6 mm. The mean length and depth of a tunneled segment for deep MB were 27.6 +/- 12.8 mm and 3.0 +/- 1.4 mm, respectively. The incidence of atherosclerotic plaques in a 2-cm-long segment proximal to MB was 16%.

Conclusion: The depiction rate of LAD-MB using DSCT in a large series of patients was 42%, with two-thirds of MB segments being the superficial type.

Keywords: CT coronary angiography; Computed tomography (CT); Conventional angiography; Coronary arteries; Dual-source CT; Myocardial bridging.

Fig. 1

Depth (A) and length (B) of tunneled segment (arrows) of left anterior descending coronary artery were analyzed on curved multiplanar reformation images using electronic caliper.

Fig. 2

Myocardial bridging was classified as superficial (A, B) or deep (C) according to depth of tunneled segment (arrows) of left anterior descending coronary artery. Superficial type was subdivided into incomplete (A) and complete (B) types according to extent of vessel encasement by myocardium.

Fig. 3

57-year-old man presented with angina. Curved (A) and short-axis (B, C) multiplanar reformation images showed two tunneled segments (short and long arrows) in mid-left anterior descending coronary artery as well as calcified plaques (arrowheads) in segment proximal to myocardial bridging (A) and in tunneled segment (A, B).

Fig. 4

57-year-old man presented with atypical chest pain. Depth (A) and length (B) of tunneled segment (arrows) of left anterior descending coronary artery were 4.4 mm and 39.3 mm, respectively. Systolic (C) and diastolic (D) curved multiplanar reformation images of tunneled left anterior descending coronary artery segment show that lumen of tunneled segment is compressed by myocardial contraction in systolic phase (C), but had normal diameter in diastolic phase (D). This phenomenon is known as 'milking effect'.