Surgery Book

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Ankle-Brachial Index

Aka: Ankle-Brachial Index, Ankle-Brachial Ratio
  1. Indications
    1. Claudication
    2. Peripheral Arterial Disease Diagnosis and Monitoring
    3. Screening for Peripheral Arterial Disease
      1. See Peripheral Arterial Disease for screening indications
  2. Efficacy
    1. Test Sensitivity: 90%
    2. Test Specificity: 98%
  3. Technique
    1. Measure highest systolic reading in both arms
      1. Record first doppler sound as cuff is deflated
      2. Record at the radial pulse
      3. Use highest of the two arm pressures
        1. Repeat the first arm Blood Pressure if there is a discrepancy between arms >10 mmHg
    2. Measure systolic readings in both legs
      1. Cuff applied to calf, just above the malleoli
        1. Avoid applying over a distal bypass site (risk of bypass thrombosis)
      2. Record first doppler sound as cuff is deflated
      3. Use doppler Ultrasound device
        1. Record dorsalis pedis pressure (absent in 2-3% of normal patients)
        2. Record posterior tibial pressure
      4. Use highest ankle pressure (DP or PT) for each leg
    3. Calculate ratio of each ankle to brachial pressure
      1. Divide each ankle pressure by highest brachial pressure
  4. Interpretation
    1. Absolute ankle pressure <50 mmHg is abnormal
    2. Ankle-Brachial Ratio >1.4: Non-compressable vessels (see false negatives below)
    3. Ankle-Brachial Ratio >0.90: Normal
    4. Ankle-Brachial Ratio <0.90: Peripheral Vascular Disease
    5. Ankle-Brachial Ratio <0.6: Intermittent Claudication
    6. Ankle-Brachial Ratio <0.5: Multi-level disease
    7. Ankle-Brachial Ratio <0.3: Limb Threatening Ischemia (requires emergent intervention)
    8. Ankle-Brachial Ratio <0.26: Resting ischemic pain
    9. Ankle-Brachial Ratio <0.2: Gangrenous extremity
  5. Interpretation: False Negative Test - Non-compressable vessels (ABI >1.4)
    1. Results in falsely elevated ankle pressure
    2. Conditions where vessels are non-compressable
      1. Diabetes Mellitus
      2. End-stage renal disease (ESRD)
      3. Diffuse arterial calcifications (as in severe or diffuse PAD)
    3. Alternative studies
      1. Toe-brachial ratio (typically 0.7 to 0.8)
  6. Management: Abnormal Ankle-Brachial Index (ABI < 0.9 or ABI>1.4)
    1. Segmental Arterial Pressure
    2. Other options
      1. Standard angiography
      2. CT angiography
      3. Magnetic resonance angiography
  7. References
    1. Hirsch (2002) Lecture, Fairview Lakes RMC
    2. Aboyans (2012) Circulation 126: 2890-909 [PubMed]
    3. Carman (2000) Am Fam Physician 61(4):1027-32 [PubMed]

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