Myocardial bridge: a bridge to atherosclerosis

Myocardial bridge (MB) is a congenital anomaly characterized by narrowing during systole of some of the epicardial coronary arterial segments running in the myocardium. Although, it is considered as a benign anomaly, it may lead to such complications as acute myocardial infarction, ventricular tachycardia, syncope, atrioventricular block and sudden cardiac death. In this study, we aimed to investigate demographic, clinical and angiographic characteristics of the patients with MB found on coronary angiography.

The present study included 71 patients with MB found on coronary angiographies performed in our institution between January 1999 and September 2003. Based on the findings on angiography, the patients were subdivided into group A (n=41) and group B (n=30). The patients in the group A had no atherosclerotic lesion and the patients in the group B had coronary artery disease in addition to MB. Angiographic, demographic and clinical characteristics of both groups were compared.

There were no differences between two groups in distribution of gender and risk factors of coronary artery disease whereas mean age of the patients in the group A was lower (47+/-5 years vs 55+/-11 years, p=0.01). Frequency of two or more risk factors for coronary artery disease in a particular patient was significantly higher in the group B (55% vs 30%, p=0.03). Myocardial bridge was located at proximal or mid segments of left anterior descending artery (LAD) in 40 patients whereas its presence in both LAD and right coronary artery was found only in one patient in group A. Mean bridging percent was 43+/-27% in group A. Localization of MB was LAD in 29 patients of group B. One patient with severe aortic valve stenosis in this group had MB at first septal branch. Mean bridging percent was 70+/-25% in group B, which was significantly higher than in group A (p<0.05). Atherosclerotic narrowing developed in only LAD in 14 patients, LAD and other vessels in 7 patients and in the vessels without MB in 9 patients. In patients with MB in LAD atherosclerotic narrowing of vessel developed proximally to the MB. Clinically, stable angina pectoris was seen more frequently in group A than group B (70% vs 35%, p=0.01), whereas the frequency of acute coronary syndrome was higher in group B (65% vs 30%, p=0.04). In regard to therapeutic approach, more patients in the group A received medical management (80% vs 50%, p=0.01), while more patients in the group B underwent surgical and percutaneous interventions (50% vs 18%, p=0.04).

Myocardial bridge probability should be considered in young patients presenting with angina or if the same symptoms are persistent in the patients without more than one risk factor for coronary artery disease. Myocardial bridge may initiate the development of atherosclerotic lesion or may facilitate progression of atherosclerosis in the proximal segment of the vessel. The risk of acute coronary syndrome rises when atherosclerosis is superimposed on MB. Myocardial bridge should be considered in the young patients, presenting with angina or its equivalents without atherosclerotic lesions on coronary angiography.