Symptomatic myocardial bridges: overview of ischemic mechanisms and current diagnostic and treatment strategies.

This review article focuses on the morphological and functional alterations that characterize patients with myocardial bridges (MB) as well as the currently available diagnostic and treatment strategies. Because of incomplete understanding of the pathophysiology of MB, their clinical significance has been the subject of debate for the last quarter century. Investigational tools now available in the cardiac catheterization laboratory have helped clarify why symptoms and signs of ischemia can occur in such patients, especially when the only angiographic finding appears to be systolic compression or milking effect of a coronary vessel. Quantitative coronary angiography and intravascular ultrasound (IVUS) clearly demonstrate that the phasic systolic vessel compression visualized on the angiogram is coupled with a persistent diastolic diameter reduction. Intracoronary Doppler reveals increased flow velocities, retrograde systolic flow, and reduced coronary flow reserve. The clinical diagnosis can be established by significant percent lumen diameter and area narrowing, increased flow velocity, and by characteristic patterns such as the "half moon" phenomenon on IVUS and the early diastolic "finger tip" phenomenon on intracoronary Doppler. Successful medical, interventional, or surgical therapy leads not only to marked improvement or normalization of these alterations but also relief of angina and ischemia.