Is myocardial bridge-related stenosis definitely a risk factor for altered coronary blood flow in patients with myocardial bridge?

Objective: To explore the potential role MBRS may play in the hemodynamics of coronary arteries and the impact of non-MBRS on hemodynamic alterations in MB patients. Methods: A total of 86 patients with MBs (located in the middle of LAD) and 50 non-MB controls were retrospectively enrolled according to coronary computed tomography angiography (CTA), coronary angiography (CA) and dynamic single-photon emission computed tomography (D-SPECT). Stenosis characteristics (incidence, location and degree of stenosis) and hemodynamics (absolute CBF, relative CBF and CFR) were compared between groups with and without MBRS (or non-MBRS). Results: Regardless of whether it was complicated by non-MBRS, there was no difference in the incidence and location of MBRS, but it varied in the severity of stenosis. Compared to cases without MBRS, cases with MBRS had increased relative CBF in the proximal and middle segments of the LAD, and the relative CBF of the left circumflex artery (LCX) was increased at rest (both P <0.05). In addition, absolute CBF in LAD was reduced in MB with non-MBRS compared to those without non-MBRS. Conclusion: MBRS can partially correct the CBF redistribution induced by the “milking effect” and increase the CBF in the LCX. Therefore, it is a possible protective factor to some extent. In addition, concomitant non-MRBS decreased the CBF of theLAD and aggravated the severity of MBRS but did not change the incidence or location of MBRS.