When to order Computed Tomography Angiography (CTA) run off versus arterial Doppler in patients with suspected peripheral artery disease?

When to Order CTA Run Off vs Arterial Doppler for Peripheral Artery Disease

For patients with suspected peripheral artery disease (PAD), arterial Doppler ultrasound should be ordered as the first-line imaging test, while CTA run off should be reserved for patients with symptomatic disease requiring revascularization or those with complex, multisegmental disease. 1

Initial Diagnostic Approach

First-Line Testing

• Ankle-Brachial Index (ABI):

  • First diagnostic test for all patients with suspected PAD
  • Results should be reported as:
    • Abnormal (≤0.90)
    • Borderline (0.91-0.99)
    • Normal (1.00-1.40)
    • Noncompressible (>1.40)

• For noncompressible arteries (ABI >1.40):

  • Toe-Brachial Index (TBI) should be measured
  • Particularly important in patients with diabetes or renal failure 1

Second-Line Imaging

• Arterial Doppler Ultrasound (Duplex Ultrasound):
  • Recommended as the first-line imaging method to confirm PAD lesions 1
  • Advantages:
    • Non-invasive
    • No radiation exposure
    • No contrast required
    • Can assess vessel wall and plaque morphology
    • High diagnostic accuracy (93.5% agreement with angiography) 2
  • Limitations:
    • Operator-dependent
    • May have difficulty visualizing deep vessels or heavily calcified arteries

When to Order CTA Run Off

CTA run off should be ordered in the following scenarios:

1. Revascularization Planning:

   • For symptomatic patients in whom revascularization is being considered 1
   • Particularly for aorto-iliac or multisegmental/complex disease 1

2. Complex Disease Assessment:

   • When detailed anatomical characterization is needed for optimal revascularization strategy 1

3. Trauma Cases:

   • First-line investigation in all patients with suspected vascular injury
   • High sensitivity (95-100%) and specificity (87-100%) 1
   • Critical time saved with CTA in trauma cases translates to decreased morbidity 1

4. Specific Vascular Conditions:

   • Suspected dissection or connective tissue vascular diseases
   • Suspected fibromuscular dysplasia (FMD) or segmental arterial mediolysis (SAM) 1

Clinical Decision Algorithm

1. Initial Assessment:

   • Measure ABI in all patients with suspected PAD
   • If ABI ≤0.90: PAD confirmed
   • If ABI >1.40: Measure TBI

2. Imaging Selection:

   • Order Arterial Doppler when:

     • Initial confirmation of PAD is needed
     • Monitoring disease progression
     • Evaluating single-segment disease
     • Screening high-risk patients

   • Order CTA Run Off when:

     • Planning revascularization (surgical or endovascular)
     • Evaluating complex, multisegmental disease
     • Assessing aorto-iliac disease
     • Evaluating trauma cases with suspected vascular injury
     • Detailed anatomical characterization is required

Important Considerations

• CTA should not be performed for anatomic assessment in asymptomatic PAD patients 1
• Both imaging modalities should be analyzed in conjunction with symptoms and hemodynamic tests prior to any invasive procedure 1
• CTA exposes patients to radiation and requires contrast, which may be contraindicated in patients with renal insufficiency 1, 3
• For patients with suspected popliteal entrapment syndrome or external iliac artery endofibrosis, either Doppler ultrasound, CTA, or MRA are appropriate initial imaging options 1

By following this evidence-based approach, clinicians can select the most appropriate imaging modality for patients with suspected PAD, optimizing diagnosis while minimizing unnecessary testing and potential complications.