Non-Invasive Assessment of Endothelial Shear Stress in Myocardial Bridges Using Coronary Computed Tomography Angiography

Myocardial bridging (MB) is a segment of coronary arteries with an intramural course, typically spared from atherosclerosis, while the adjacent proximal segment is reported to be atherosclerosis-prone, a phenomenon contributed to local endothelial shear stress (ESS). We aimed to describe the ESS milieu in coronaries with MBs combining coronary computed tomography angiography with computational fluid dynamics and to investigate the association of atherosclerosis presence proximal to MBs with hemorheological characteristics. Patients (n = 36) were identified and 36 arteries with MBs (11 deep and 25 superficial) were analyzed. ESS did not fluctuate 5 mm proximally to MBs vs 5 mm within MBs (0.94 vs 1.06 Pa, p = .56). There was no difference when comparing ESS in the proximal versus mid versus distal MB segments (1.48 vs 1.37 vs 1.9 Pa, p = ns). In arteries with plaques (n = 12), no significant ESS variances were observed around the MB entrance, when analyzing all arteries (p = .81) and irrespective of morphological features of the bridged segment (deep MBs; p = .65, superficial MBs; p = .84). MBs are characterized by homogeneous, atheroprotective ESS, possibly explaining the absence of atherosclerosis within bridged segments. The interplay between ESS and atherosclerosis is potentially not different in arteries with MB compared with arteries without bridges.

Automated summary

Myocardial bridging (MB) is a segment of coronary arteries that is usually free from atherosclerosis, while the adjacent proximal segment is prone to it due to local endothelial shear stress (ESS). This study used coronary computed tomography angiography and computational fluid dynamics to analyze the ESS in coronary arteries with MBs and investigate the association between atherosclerosis and hemorheological characteristics. The results showed that there was no significant difference in ESS between the proximal 5 mm to MBs and the region within MBs. No significant ESS variances were observed around the MB entrance in arteries with plaques, regardless of the morphological features of the bridged segment. MBs have homogeneous, atheroprotective ESS, which may explain the absence of atherosclerosis within bridged segments. The interplay between ESS and atherosclerosis is potentially similar in arteries with MB compared to those without bridges.