Systolic luminal narrowing and morphologic characteristics of myocardial bridging of the mid-left anterior descending coronary artery by dual-source computed tomography

To identify factors that can affect systolic compression of myocardial bridging (MB) of the mid-left anterior descending (LAD) coronary artery with dual-source computed tomography (DSCT). Patients with mid-LAD MB (n = 198) detected by DSCT were studied. MB was classified as incomplete superficial (IS), complete superficial (CS), and deep (D) type. The depth and length of the mid-LAD MB segment in diastole, luminal reduction of the tunneled LAD segment in systole, and degree of systolic left ventricular (LV) wall thickening were all analyzed. Correlation between the depth, length, degree of systolic LV wall thickening, and luminal narrowing in the systolic phase was evaluated. Eighty-one (40.9%) MB were IS, 37 (18.7%) were CS, and 80 (40.4%) were D type. Significant differences in the degree of luminal narrowing in the systolic phase were found among the three MB types (IS, 19.9 ± 10.1%; CS, 26.9 ± 12.1%; D, 36.6 ± 13.8%; P < 0.0001). The luminal narrowing in the systolic phase correlated with the depth (r = 0.56) and percentage of systolic LV wall thickening (r = 0.44), but was not related to length (r = 0.28). In addition to the degree of LV systolic wall thickening and depth of MB, the types of MB also affect luminal narrowing in the systolic phase.