Abstract 11954: Coronary Atherosclerotic and Inflammatory Changes for Varying Lengths of Myocardial Bridge

Abstract

Background: Myocardial bridge (MB) is a frequent cause of ischemia and nonobstructive coronary artery disease (INOCA). Coronary segments proximal to the MB likely develop atherosclerotic lesions due to altered endothelial shear stress (ESS) as a consequence of systolic compression beneath MB. We recently demonstrated that optical coherence tomography (OCT)-delineated adventitial vasa vasorum (AVV) formation as a marker for vascular inflammation are extensive at the segments proximal to the MB. This study was aimed to examine coronary atherosclerotic and inflammatory changes depending on varying MB length. Methods and Results: Amongst 165 INOCA patients who underwent both coronary computed tomography angiography (CCTA) and co-registered OCT, 31 subjects with CCTA-derived MB in the left anterior descending coronary arteries were enrolled ( Fig. A ). Biplane coronary angiography was merged with serial OCT cross-sections to be three-dimensionally volume-rendered for the ESS mapping ( Fig. B ). Using OCT, tissue type of each coronary segment was classified as intimal hyperplasia (IT), fibrous plaque (FP), fibroatheroma (FA), or fibrocalcific plaque (FC). The segment proximal to the MB was with the lowest ESS level, where OCT displayed the lesion with FA ( Fig. B ). Indeed, advanced lesions with FA and FC were more frequently noted at the sites 5-mm proximal to the MB when compared to the middle portions beneath MB ( Fig. C ). Notably, % intimal plus medial (I+M) area = [(I+M area/vessel area) х100] as a marker for atherosclerotic changes were correlated with the lengths of MB at the proximal segments ( Fig. D ). Lesions with FP, FA and FC showed longer MB lengths as compared with IT (One-way ANOVA. P<0.05). Likewise, AVV formation was positively correlated with the length of MB ( Fig. E ). Conclusion: These results indicated that in addition to the ESS, varying MB lengths alter atherosclerotic and inflammatory coronary lesions proximal to the MB.