What is myocardial bridging, and is it important?
The coronary arteries are located in the epicardial fat, which is a fat layer deep to the pericardium but superficial to the myocardium. Myocardial bridging is present if a coronary artery courses into the myocardium and is surrounded by muscle for part of its course.
The significance of myocardial bridging is that, theoretically, an artery surrounded by myocardium may be compressed when the myocardium contracts during systole (systolic compression), limiting blood supply and causing myocardial ischemia. Catheter angiography has difficulty in identifying myocardial bridging unless there is associated systolic compression since the myocardium is not depicted. Until more recently, myocardial bridging was rarely diagnosed. Coronary CTA shows myocardial bridging in 25% to 40% of patients, most commonly in the LAD coronary artery. If multiphase data are available, the vessel should be viewed in systole to ensure that there is no systolic compression. Myocardial bridging in the absence of systolic compression is almost always an incidental finding without clinical significance. Systolic compression may be more likely in cases in which the bridged arterial segment is relatively long and is located deep within the myocardium.