Myocardial bridge as a cause of myocardial ischemia and infarction: “Bridge over troubled waters” and turbulent coronary blood flow

Abstract

Myocardial bridge (MB) is a congenital coronary anomaly that is anatomically well recognized since the sixteenth century. Although, this condition is frequently asymptomatic, MB may be responsible for adverse ischemic-related complications including angina, myocardial ischemia, acute myocardial infarction, left ventricular dysfunction, cardiac arrhythmias, and even sudden cardiac death. The incidence of MB varies depending on the method of detection. It may vary from 1.5 to 16% when analyzed by angiography and up to 80% when assessed by autopsy. Flow alterations and turbulent coronary blood flow due to the MB can develop accelerated atherosclerosis in the coronary segment immediately proximal to the bridged segment. Other important factors to contemplate are the concomitant number of affected arteries or tunneled segments, and the degree of reduction in lumen diameter during systolic contraction or kinking. First-line therapy involves pharmacological treatment with beta-blockers and calcium-channel blockers, while nitrates are contraindicated due to adverse increase in heart rate and myocardial hypercontractility from reflex sympathetic activation. Non-pharmacological therapy, namely, surgical intervention and percutaneous coronary intervention with implantation of diluted stents should only be considered as a therapeutic option in patients with MB refractory to medical therapy and documented myocardial ischemia. A large, prospective randomized clinical trial is required to identify the best treatment strategy for patients with myocardial bridging.