Abstract 17154: Impact of Myocardial Bridging on Coronary Endothelial Dysfunction and Atherosclerotic Plaque Formation
Background: Recent studies have demonstrated that myocardial bridging (MB) can cause adverse outcomes, presumably resulted from hemodynamic disturbance that leads to endothelial dysfunction at the affected segment and accelerated atherosclerosis in the segment proximal to the MB. The aim of this study was to characterize the extent and degree of endothelial dysfunction in relation to the location and severity of MB in human left anterior descending arteries.
Methods: IVUS and endothelial function testing were performed in 120 patients with angiographically non-obstructed coronary arteries. MB was defined by IVUS as an echolucent muscle band (halo) partially surrounding the artery. Arterial compression at the MB segment was evaluated as a systolic decrease in external elastic membrane (EEM) area standardized by diastolic EEM area. Plaque burden was measured at both MB segment and adjacent 20-mm proximal reference. By measuring the minimum lumen diameter using quantitative coronary angiography, endothelial dysfunction was estimated according to the paradoxical diameter response to acetylcholine (Ach).
Results: IVUS identified MBs in 68 patients (56.7%) (age: median 53, range: 20-77; male: 25%). In the MB patients, maximum plaque burden was significantly larger in the proximal reference than in the MB segment (Figure: left). In contrast, the paradoxical Ach response was significantly greater in the MB segment, compared with its proximal reference as well as the proximal 50-mm segment in the non-MB patients (Figure: right). Arterial compression showed a weak but significant correlation with the paradoxical Ach response at the MB segment (r=0.296, p=0.014), but not at the proximal reference (r=0.149, p=0.226).
Conclusion: While relatively spared from plaque formation, coronary segments under MB showed localized endothelial dysfunction. The degree of this impairment appears to be related to the severity of arterial squeezing during the cardiac cycle.
- © 2013 by American Heart Association, Inc.