Objective To investigate the value of transluminal attenuation gradient (TAG) measured by coronary computed tomography angiography (CCTA) in predicting systolic compression of myocardial bridge (MB).

Methods Between January 2017 and December 2019, clinical data of patients diagnosed with MB by both CCTA and invasive coronary angiography (ICA) within one month were collected and analyzed retrospectively. According to their ICA findings, patients were divided into three groups: patients without systolic compression, patients with systolic compression < 50%, and patients with systolic compression ≥50%. TAG was defined as the linear regression coefficient between the contrast agent concentration of the luminal attenuation in the coronary artery and the length from the vessel ostium. By measuring the length and depth of MB, as well as the TAG of MB vessels, the relationship between these three parameters and the degree of systolic compression detected by ICA was explored.

Results Totally, 244 patients meeting the inclusion criteria were included. TAG showed a linear correlation (r=-0.53, P < 0.001) in the three groups of patients without MB systolic compression, MB systolic compression < 50% and MB systolic compression ≥50%, with values of(-9.56±4.11) HU/10 mm, P < 0.001, (-13.35±5.82) HU/10 mm, P < 0.001 and(-17.48±6.97) HU/10 mm, P < 0.001. In contrast, there was no significant correlation between the length or depth of MB and the degree of the systolic compression of MB. When the best cut-off value of TAG was determined by ROC curve analysis as -14.8 HU/10 mm, area under curve was 0.801, and its diagnostic accuracy (82.0%) were higher than those of the other two control groups.

Conclusions TAG measured by coronary CTA can predict systolic compression of myocardial bridge. However, the length or depth of MB is not very accurate in predicting the degree of the systolic compression of myocardial bridge.