What are the recommended diagnostic tests and treatment options for cardiac bridging?

Diagnostic Testing and Treatment for Cardiac Bridging

Coronary computed tomography angiography (CCTA) is the recommended initial non-invasive test for diagnosing myocardial bridging, followed by invasive coronary angiography with intracoronary Doppler flow measurement for functional assessment in symptomatic patients. 1

Diagnostic Approach

Initial Evaluation

• Suspect myocardial bridging in patients with:
  • Exertional chest pain or angina
  • Unexplained QRS or ST-T wave changes
  • Syncope during or after physical activity
  • Symptoms that worsen with exercise
  • Young patients with chest pain resembling angina

First-Line Diagnostic Tests

1. Resting 12-lead ECG

   • Recommended for all patients with chest pain 1
   • May show ischemic changes during symptomatic episodes

2. Non-invasive functional imaging

   • Coronary CTA: Preferred initial test for visualizing the tunneled segment 1, 2
   • Stress testing options:
     • Exercise ECG test (useful for assessing exercise tolerance and symptoms) 1
     • Stress echocardiography (dobutamine)
     • Myocardial perfusion scintigraphy

Definitive Diagnostic Tests

1. Invasive coronary angiography

   • Gold standard for diagnosis 1
   • Characteristic finding: systolic compression of coronary artery (typically LAD)
   • Indicated even with negative exercise tests in young patients with cardiac arrest history 1

2. Advanced invasive assessment

   • Intracoronary Doppler flow velocity measurement: Evaluates hemodynamic significance 1, 2
   • Intravascular ultrasound (IVUS): Reveals diastolic flow abnormalities and vessel compression 3, 2

Treatment Algorithm

First-Line Treatment

1. Medical therapy (for symptomatic patients):
   • Beta-blockers: First-line medication 1, 3, 2
   • Non-dihydropyridine calcium channel blockers: Alternative first-line option 2
   • AVOID nitrates: Can worsen symptoms by increasing systolic narrowing 1, 2

Second-Line Treatment (for patients refractory to medical therapy)

Consider invasive management for patients with:

• Persistent symptoms despite optimal medical therapy
• Evidence of significant myocardial ischemia
• Life-threatening arrhythmias

Options include:

1. Surgical myotomy (unroofing):

   • First surgical choice for isolated myocardial bridging 1, 4, 5
   • Success rate: 63% of patients report no chest pain after surgery 5

2. Coronary artery bypass grafting (CABG):

   • Alternative when myotomy is not feasible 4
   • Consider for patients with concomitant coronary artery disease

3. Intracoronary stenting:

   • Limited long-term data on outcomes 2
   • Risk of stent fracture due to external compression

Special Considerations

Risk Stratification

• Higher risk features include:
  • Long and deep myocardial bridges
  • Bridges in patients with hypertrophic cardiomyopathy (present in 30-50%) 1
  • Endothelial dysfunction in the bridged segment 5
  • Multiple simultaneous bridges 6

Complications to Monitor

• Myocardial ischemia
• Ventricular arrhythmias
• Atrioventricular block
• Myocardial infarction
• Sudden cardiac death (rare but reported, especially during intense exercise) 1, 6

Follow-up After Treatment

• For patients undergoing surgery:
  • Post-operative exercise testing to assess for persistent ischemia 4
  • Follow-up angiography to confirm restoration of coronary blood flow 4
• For medically managed patients:
  • Regular assessment of symptom control
  • Consideration of activity modification for athletes with significant bridging 6

Common Pitfalls

• Misdiagnosing chest pain as non-cardiac when caused by myocardial bridging
• Using nitrates, which can worsen symptoms in patients with myocardial bridging
• Failing to consider myocardial bridging in young athletes with exertional symptoms
• Underestimating the clinical significance of bridges in symptomatic patients

Myocardial bridging is often considered benign but can cause significant symptoms and rarely life-threatening complications. Appropriate diagnostic testing and targeted treatment can significantly improve outcomes and quality of life.