Settlement of Stenotic Site and Enhancement of Risk Factor Load for Atherosclerosis in Left Anterior Descending Coronary Artery by Myocardial Bridge.

ABSTRACT

OBJECTIVE: The aim of this study was to investigate the influence of a myocardial bridge (MB) on atherosclerosis development in the left anterior descending artery of the normal heart and the importance of traditional risk factors (RFs). An additional objective was to determine the correlation between intimal thickening and luminal narrowing. APPROACH AND RESULTS: The left anterior descending artery from 150 autopsied hearts was treated with formalin perfusion fixation, and each left anterior descending artery was serially cross-sectioned. The intima-media and luminal stenosis ratios were examined using computer-assisted histomorphometry. The luminal stenosis ratio was closely correlated with the intima-media ratio (r=0.792; P<0.001). When an MB was present, the luminal stenosis ratios proximal to the MB in the RF (+) group were significantly greater than those in the RF (-) group (P=0.022 by a multiple comparison test), but there were no differences between the RF (+) and RF (-) groups when an MB was absent. In addition, the site of the greatest stenosis in the MB (+) RF (+) group was 2.5 cm proximal to the MB entrance. Multivariate analyses indicated that age was an independent factor for luminal stenosis ratios ≥50% and 60% (P=0.002 and 0.029, respectively). Furthermore, the presence of an MB plus RFs was an independent factor for a luminal stenosis ratio ≥70% (P=0.037). CONCLUSIONS: An MB enhances left anterior descending artery atherosclerosis development at a site proximal to the MB entrance, particularly in subjects who have some RFs.