Acute coronary syndrome caused by myocardial bridging

Myocardial bridging (MB) is a phenomenon that occurs when coronary arteries course through myocardial tissue rather than, as is normal, on the surface of the myocardium. Although often asymptomatic, contraction of the myocardium in the presence of a myocardial bridge can sometimes occlude the lumen of coronary arteries that penetrate the myocardium, resulting in symptoms, signs, and electrocardiographic changes indistinguishable from those associated with acute coronary syndromes (ACS) caused by intraluminal narrowing of coronary arteries or coronary artery plaque rupture. In this monograph, we present the case of a 45-year-old man who presented to the emergency department with typical chest pain accompanied by electrocardiographic changes consistent with acute occlusion of the left anterior descending artery. During percutaneous coronary intervention, fluoroscopically-obtained cine image loops revealed evidence of dynamic coronary artery narrowing due to myocardial bridging. There was no evidence of static coronary artery occlusion. Myocardial bridging is typically managed medically when symptomatic, although refractory cases may ultimately require invasive or surgical intervention. Given that emergency physicians are frequently the first providers to evaluate patients with acute coronary syndromes, myocardial bridging as an etiology for ACS is a clinical entity of which emergency physicians should be aware.