Objective To explore the effect of myocardial bridge (MB) on non-invasive fractional flow reserve (FFRCT) and wall shear stress (WSS) using coronary CT angiography (CTA) and computational fluid dynamics (CFD).

Methods From May 2020 to December 2020, 50 patients with MB in left anterior descending artery and 25 controls undergoing coronary CTA in Zhongshan Hospital, Fudan University were included. Patients were divided into superficial (n=25) and deep MB groups (n=25) according to the depth of MB. The differences in anatomical characteristics, FFRCT values, and WSS values among groups were analyzed. The MB group was divided into normal FFRCT (>0.8) and abnormal FFRCT (≤ 0.8) groups according to FFRCT values. The differences in clinical symptoms, anatomical characteristics, and WSS values between the two groups were analyzed.

Results Compared to control group, the FFRCT values of superficial and deep MB groups decreased in diastolic phase and systolic phase (P < 0.001); the WSS values of coronary artery distal to MB were higher in superficial and deep groups in both phases (P=0.037, 0.002). A significant difference in systolic MB compression index was found between normal FFRCT and abnormal FFRCT groups (P=0.023). Patients with abnormal FFRCT were more likely to have angina (30.8% vs 8.3%, P=0.048).

Conclusions The FFRCT values of MB patients are lower than those of controls. The WWS values of coronary artery distal to MB are higher than those of controls. The increase of systolic myocardial bridge compression index has a association with the decrease of FFRCT values. Patients with abnormal FFRCT values are more likely to have angina.