What is the role of a CT (Computed Tomography) scan in evaluating cardiac bridging, particularly in patients on anticoagulation therapy?

Role of CT Scan in Evaluating Cardiac Bridging

CT scanning is the preferred non-invasive imaging modality for evaluating cardiac bridging, particularly in patients on anticoagulation therapy, due to its high spatial resolution and ability to directly visualize the bridged myocardium and assess its anatomical characteristics. 1

What is Cardiac Bridging?

Cardiac bridging (myocardial bridging) is an anatomical variant where a segment of a coronary artery, most commonly the left anterior descending artery (LAD), tunnels through the myocardium rather than running on the epicardial surface. This can lead to vessel compression during systole, potentially causing symptoms in some patients.

Advantages of CT for Cardiac Bridging Assessment

• Superior Detection: CT has significantly higher detection rates (22%) compared to conventional coronary angiography (6%), approaching the prevalence found in autopsy studies (42%) 2

• Detailed Anatomical Characterization: CT can precisely measure:

  • Length of the bridged segment (average 19.3 mm)
  • Depth of the myocardial tissue covering the artery (average 2.47 mm)
  • Degree of systolic compression
  • Presence of atherosclerotic plaque proximal to the bridge 1, 3

• Classification Capability: CT allows classification of bridges as complete or incomplete based on the continuity of myocardium over the tunneled segment 3

• Safety Profile: Particularly beneficial for patients on anticoagulation therapy as it avoids the procedural risks associated with invasive catheter angiography 3

CT Protocol for Cardiac Bridging

• ECG-gated cardiac CT with contrast is the optimal technique 4
• Acquisition during both systole and diastole to assess dynamic compression
• High spatial resolution (submillimeter) to accurately measure bridge depth and length
• 3D multiplanar reformatting for optimal visualization

Clinical Applications in Patients on Anticoagulation

For patients on anticoagulation therapy, CT offers several advantages:

1. Reduced Bleeding Risk: Non-invasive nature eliminates the risk of access site bleeding complications associated with invasive angiography

2. Comprehensive Assessment: Beyond bridging, CT can simultaneously evaluate:

   • Coronary artery disease
   • Cardiac function and morphology
   • Other cardiac or thoracic abnormalities 1

3. Procedural Planning: If intervention is needed, CT provides detailed anatomical information for planning 4

Limitations

• Radiation Exposure: Though modern CT scanners have reduced radiation doses significantly
• Contrast Administration: Potential for contrast-induced nephropathy in at-risk patients
• Limited Functional Assessment: While CT can show anatomical compression, functional assessment of hemodynamic significance may require additional testing

Clinical Pathway for Suspected Cardiac Bridging

1. Initial Evaluation: Patients with chest pain, particularly those with exertional symptoms and normal/non-obstructive coronary arteries on initial testing

2. Imaging Selection:

   • ECG-gated cardiac CT with contrast as first-line imaging for suspected bridging
   • Consider CT in patients with inconclusive stress tests or invasive angiography

3. Management Decisions: Based on CT findings (bridge length, depth, compression severity) and clinical symptoms

Conclusion

CT scanning represents the optimal non-invasive approach for evaluating cardiac bridging, particularly in patients on anticoagulation therapy where avoiding invasive procedures is preferable. Its ability to directly visualize the bridge and provide detailed anatomical information makes it superior to conventional angiography for this specific condition.