Myocardial bridging, from a simple benign condition to sudden cardiac death

Abstract

Myocardial Bridging represents an anomaly of the coronary circulation, characterized by a myocardic course of a major epicardial artery. The segment is referred to as the “tunnelled artery” as it runs beneath a layer of muscle fibbers, which varies in length and thickness. The most common site of this anomaly is the left anterior descending artery, but it can also be confined to any other coronary branches. The condition is clinically silent most of the times, being accidentally discovered during an angiographic study or at autopsies. Even though usually benign, clinical manifestations vary from ischemia to sudden cardiac death. Superficial bridges are usually of no clinical importance, while deep ones lead to different cardiac complications. The estimated frequency varies from 1.5% to 16% at coronary angiography studies, to 80% in some autopsy studies. While still debated whether just an anatomic variant or a malignant condition, different pathology studies showed morphologic alteration of the myocardium tributary to the bridged artery. Furthermore, there is evidence that the tunnelled artery is protected from atherosclerosis, while the proximal and distal segments have an increase susceptibility to atheroma plaque formation. The main physiologic effect of the myocardial bridge occurs with each systole, when the coronary artery is compressed between the overlying muscle bundle and the rest of the ventricular mass. Yet, additional research is needed to define which bridges are life-threatening and furthermore, which are the most suitable therapy options for these patients. Our goal was to review the literature regarding Myocardial Bridging and present two opposite clinical cases, one discovered by chance after the autopsy and the other of sudden cardiac.