Coronary Endothelial Dysfunction and Vasomotor Dysregulation in Myocardial Bridging

Myocardial bridging (MB), a congenital variant where a coronary artery segment is tunneled within the myocardium, is increasingly recognized as a contributor to coronary endothelial and vasomotor dysfunction. Beyond the hallmark systolic compression observed on angiography, MB disrupts endothelial integrity, impairs the release of vasoactive substances, and induces vasomotor abnormalities. These effects exacerbate ischemic symptoms and predispose to atherosclerosis in the proximal segment, particularly in conditions such as ischemia/myocardial infarction with nonobstructive coronary arteries. Recent studies underscore MB's association with coronary vasospasm, microvascular endothelial dysfunction, and adverse cardiovascular outcomes, including sudden cardiac death. These findings highlight the interplay between MB's structural anomalies and functional impairments, with factors such as the bridge's length, depth, and orientation influencing its hemodynamic significance. Advances in imaging and coronary physiology assessment, including acetylcholine testing and stress diastolic fractional flow reserve/iFR/RFR, have enhanced diagnostic precision. This review explores the multifaceted impact of MB on coronary physiology, emphasizing its role in endothelial dysfunction and vasomotor regulation. Recognizing MB's contribution to cardiovascular disease is essential for accurate diagnosis and tailored management strategies aimed at mitigating ischemic risk and improving patient outcomes.