What is a Myocardial Bridge?
A myocardial bridge is a congenital coronary anomaly where a segment of an epicardial coronary artery runs intramurally through the myocardium rather than along the surface of the heart, causing the overlying muscle to compress the vessel during systolic contraction. 1
Anatomical Definition and Prevalence
The muscle overlying the artery is termed the "myocardial bridge," while the intramyocardial segment is called the "tunneled artery." 2
The left anterior descending artery (LAD) is affected in almost all cases, making it the predominant location for this anomaly. 1, 3
There is a striking discrepancy between detection methods: angiography identifies myocardial bridging in only 0.5-4.5% of patients, while pathological studies reveal its presence in 15-85% of cases, indicating most bridges are clinically silent. 1, 3
Pathophysiology and Clinical Significance
The typical angiographic presentation shows systolic compression of the coronary artery during the cardiac cycle, which is the hallmark finding. 1
While most myocardial bridges are asymptomatic and clinically benign, they can cause myocardial ischemia through two distinct mechanisms: direct systolic compression with delayed diastolic relaxation reducing coronary flow reserve, and enhancement of atherosclerotic plaque formation in the segment proximal to the bridge due to abnormal hemodynamics. 4, 5
Pathological studies indicate that vessels with a tunneled length that is long and deeper than 3 mm beneath the epicardium create the greatest vulnerability for adverse cardiac events. 1
Myocardial bridging can rarely lead to serious complications including myocardial infarction, ventricular tachyarrhythmias, atrioventricular block, and sudden cardiac death. 1, 6
Special Population Considerations
Myocardial bridging occurs in 30-50% of patients with hypertrophic cardiomyopathy and has been implicated as a potential contributor to sudden cardiac death in this high-risk population. 1, 3
The anomaly should be considered in young patients, particularly males, who present with exertional chest pain or syncope, especially when accompanied by unexplained ECG changes. 1
Clinical Context
Although traditionally considered a benign variant, increasing recognition of specific subsets associated with ischemic symptoms has elevated the clinical importance of myocardial bridging. 2, 7
The anatomical properties of the bridge—including its length, thickness, and location—determine both the magnitude of hemodynamic effects and the choice of treatment approach. 4