Myocardial bridging on coronary CTA: An innocent bystander or a culprit in myocardial infarction?

Abstract

Myocardial bridging describes the clinical entity whereby a segment of coronary artery is either partially or completely covered by surrounding myocardium. It represents the most frequent congenital coronary anomaly and has an estimated prevalence of ≤13% on angiographic series. With the emergence of cardiac computed tomography and its ability to simultaneously image the coronary arteries and also the myocardium, there has been an apparent increase in the detection rates of myocardial bridges (prevalence as high as 44%). It has now become important to evaluate their clinical significance. Myocardial bridging is generally considered a benign entity with survival rates of 97% at 5 years; however, there is now emerging evidence that certain myocardial bridge characteristics may be associated with cardiovascular morbidity. The length and depth of myocardial bridges have been associated with increased atherosclerosis, whereas the degree of systolic compression has been associated with ischemia on myocardial perfusion single-photon emission tomography. On the basis of current evidence, it appears that limiting further testing for ischemia to symptomatic patients with long and/or deep myocardial brides would be appropriate.

Angiographically evident atherosclerotic stenosis associated with myocardial bridging (MB) and risk factors for the artery stenosis located proximally to MB: an observational study

“…In present study, the most frequently involved MB segment was the middle LAD and the number of male with MB was higher, which were consistent with previous researches (14,16,19,26). DVDs in MB segments were significantly smaller than in proximal reference segments, and even, smaller than in distal reference segments.…”

“…This phenomenon is considered as resulting from the limit of MB to the diastolic dimensions of the external elastic membrane and lumen of MCA (29). The higher proportion of lesions located proximally and obvious lower proportion of lesions located distally to MB was found in present study, which were consistent with previous studies (14,15,19,30). At present the exact mechanism of MCA and distal segment of the bridged artery usually free from atherosclerosis remains unclear.…”

“…The following complications have been reported as acute coronary syndrome (4)(5)(6)(7)(8), cardiac arrhythmia (9, 10), stunning and sudden death (11,13). It widely accepts that the intramural and distal portions of a bridged artery usually remain free from atherosclerotic disease, which may be explained by protective effects of MB and atherosclerosis may be more frequent in segments proximal to the bridging (14)(15)(16)(17)(18)(19)(20). These changes in atherosclerotic distribution have been recognized in autopsy, pathology and clinical imaging studies (14)(15)(16)(17)(18)(19)(20).…”

Congenital coronary artery anomalies in adult population detected using dual source ECG-gated CTA in a single institution

“…However, the relationship between MB anomaly and increased cardiovascular morbidity is still unclear. According to previous reports [21,30], the MB may cause coronary heart disease by two mechanisms. First, by a direct systolic compression of the tunnelled segment and second by the enhanced atherosclerotic plaque formation occurring because of alteration of haemodynamic factors, mainly in the vessel segment proximal to the bridge.…”

“…First, by a direct systolic compression of the tunnelled segment and second by the enhanced atherosclerotic plaque formation occurring because of alteration of haemodynamic factors, mainly in the vessel segment proximal to the bridge. The length, the depth and the location of the MB have been associated with the mechanisms above [21,30]. Therefore, MB is classified as superficial or deep, depending on the thickness of the covering muscular layer (≤ 1 mm or > 1 mm) [26].…”