Are arterial dopplers (Arterial Doppler Ultrasound) and Ankle-Brachial Index (ABI) the same thing?

Arterial Doppler Ultrasound vs. Ankle-Brachial Index (ABI): Different Diagnostic Tools for Peripheral Arterial Disease

No, arterial Doppler ultrasound and ankle-brachial index (ABI) are not the same thing—they are distinct but complementary diagnostic tools used in the evaluation of peripheral arterial disease (PAD). 1, 2

Understanding the Differences

Ankle-Brachial Index (ABI)

• Definition: A ratio calculated by dividing the highest systolic pressure in the ankle (from either posterior tibial or dorsalis pedis artery) by the highest systolic brachial pressure
• Measurement method: Performed using a blood pressure cuff and a Doppler device to detect blood flow
• Interpretation:
  • Normal: 1.00-1.40
  • Borderline: 0.91-0.99
  • Abnormal (PAD): ≤0.90
  • Noncompressible vessels: >1.40

Arterial Doppler Ultrasound

• Definition: An imaging technique that uses ultrasound to visualize blood flow through arteries
• Purpose: Assesses arterial anatomy, locates stenotic lesions, and evaluates hemodynamics
• Role: Used after ABI confirms PAD diagnosis to plan revascularization or further treatment

Relationship Between the Two Tests

• The ABI measurement process uses a Doppler ultrasound device as a tool to detect blood flow signals when measuring systolic pressures 1
• However, a complete arterial Doppler ultrasound study is a more comprehensive imaging examination that:
  • Visualizes arterial anatomy
  • Identifies location and severity of stenoses
  • Assesses blood flow patterns
  • Provides waveform analysis 1, 2

Clinical Application and Diagnostic Pathway

1. Initial Screening: ABI is the first-line non-invasive test for diagnosing PAD 2

   • Simple, low-cost, and widely available
   • Sensitivity 68-84% and specificity 84-99% for PAD diagnosis 1

2. When ABI is Abnormal or Inconclusive:

   • If ABI ≤0.90: PAD diagnosis confirmed
   • If ABI >1.40 (noncompressible vessels): Perform toe-brachial index (TBI)
   • If clinical suspicion remains despite normal ABI: Consider exercise ABI or imaging

3. Role of Arterial Doppler Ultrasound:

   • Used after PAD diagnosis to assess arterial anatomy
   • Helps determine revascularization strategy
   • Provides detailed anatomical and hemodynamic information 1, 2

Technical Considerations

• ABI measurement reliability:

  • Doppler method is more reliable than oscillometric or palpation methods 1
  • Intraobserver coefficient of variation with Doppler method varies widely but is superior to oscillometric methods 1
  • Skilled examiners achieve better reproducibility 1

• Common pitfalls:

  • Noncompressible vessels (common in diabetes and CKD) may falsely elevate ABI >1.40 1
  • In such cases, toe-brachial index (TBI) is recommended as digital arteries are rarely noncompressible 1
  • Proper technique is essential for accurate results 1

Clinical Implications

• ABI is a valuable screening tool that provides prognostic information beyond PAD diagnosis
• An abnormal ABI (≤0.90) identifies patients at increased risk of cardiovascular events and mortality 2
• Arterial Doppler ultrasound provides anatomical information needed for treatment planning
• Both tests are complementary in the comprehensive evaluation of patients with suspected PAD

In summary, while a handheld Doppler device is used during ABI measurement, a complete arterial Doppler ultrasound study is a distinct diagnostic procedure that provides more comprehensive anatomical and hemodynamic information about arterial disease.