Diagnosis and Management of Myocardial Bridging
Myocardial bridging is best diagnosed through coronary angiography showing characteristic systolic compression of a coronary artery (typically the left anterior descending artery), with additional functional assessment through stress testing or intracoronary measurements to determine hemodynamic significance in symptomatic patients. 1, 2
Definition and Anatomy
- Myocardial bridges consist of muscle fiber bundles overlying an epicardial coronary artery for a variable distance
- Most commonly affects the left anterior descending artery
- Reported incidence varies significantly between angiographic studies (0.5-4.5%) and pathological studies (15-85%) 1
- Typical presentation is systolic compression of the artery during the cardiac cycle
Diagnostic Approach
Initial Diagnostic Tests
- Coronary angiography: Gold standard for diagnosis, showing characteristic "milking effect" or systolic narrowing of the coronary artery 1, 2
- ECG exercise test: To evaluate for exercise-induced ischemia 1
- Dobutamine stress echocardiography: Can reveal wall motion abnormalities in the territory of the bridged artery 1
- Myocardial perfusion scintigraphy: May demonstrate perfusion defects in symptomatic patients 1
Advanced Diagnostic Modalities
- Computed Tomography Coronary Angiography (CTCA): Allows direct visualization of the myocardial bridge and measurement of bridge length and depth 1, 3
- Intracoronary Doppler flow velocity measurement: Shows characteristic "finger-tip" phenomenon with rapid early diastolic flow, mid-diastolic plateau, and end-diastolic flow acceleration 1, 2
- Intravascular ultrasound (IVUS): Can demonstrate the "half-moon" phenomenon and assess vessel compression 3
- Quantitative coronary angiography: Shows delayed and incomplete vessel diameter gain during mid to late diastole in symptomatic patients 1
Clinical Significance Assessment
- Identification of the presence and evaluation of the severity of myocardial bridges is clinically important 1
- Most bridges are benign, but some can cause:
Risk Stratification
- Higher risk features include:
- Deep bridges (>3 mm beneath epicardium)
- Long tunneled segments
- Presence of symptoms (especially angina or syncope)
- Evidence of myocardial ischemia on functional testing
- Association with hypertrophic cardiomyopathy (present in 30-50% of HCM patients) 1
Management Approach
Medical Management
- Beta-blockers: First-line treatment for symptomatic patients 1, 2
- Reduce heart rate, prolong diastole, and decrease contractility
- Calcium channel blockers: Alternative when beta-blockers are contraindicated 2
- AVOID nitrates: Can worsen symptoms by increasing systolic narrowing 1, 2
Invasive Management (for refractory symptoms)
- Surgical myotomy: Unroofing of the bridged segment 1, 2
- Coronary artery bypass grafting: Alternative surgical approach 1, 2
- Stenting: May be considered but has limitations due to risk of stent fracture 1, 2
Special Considerations for Athletes
- Asymptomatic athletes with incidental myocardial bridging can participate in competitive sports 1
- Symptomatic athletes should undergo assessment for inducible myocardial ischemia 1
- Athletes with evidence of myocardial ischemia should be treated before sports participation 1
- After surgical repair, sports participation can resume after complete sternal healing and testing showing no evidence of ischemia or complex ventricular arrhythmias 1
Follow-up Recommendations
- Regular clinical assessment of symptom control
- Consider repeat functional testing if symptoms worsen
- For patients who have undergone intervention, follow standard post-procedure monitoring protocols 2
Myocardial bridging is often an incidental finding but requires careful evaluation in symptomatic patients to determine its hemodynamic significance and appropriate management strategy.