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Ankle-Brachial IndexAka: Ankle-Brachial Ratio

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
2. Measure systolic readings in both legs
  1. Cuff applied to calf
  2. Record first doppler sound as cuff is deflated
  3. Use doppler ultrasound device
    1. Record dorsalis pedis pressure
    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 by highest brachial pressure
Interpretation
1. Ankle-Brachial ratio >1.3: Non-compressable vessels (see false negatives below)
2. Ankle-Brachial ratio >0.95: Normal
3. Ankle-Brachial ratio <0.95: Peripheral Vascular Disease
4. Ankle-Brachial ratio <0.6: Intermittent Claudication
5. Ankle-Brachial ratio <0.5: Multi-level disease
6. Ankle-Brachial ratio <0.26: Resting ischemic pain
7. Ankle-Brachial ratio <0.2: Gangrenous extremity
False Negative Test: Non-compressable vessels (ABI 1.3 to 1.5)
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)
Management: Abnormal ankle-brachial index (ABI < 0.9 or ABI>1.3)
1. Segmental Arterial Pressure
2. Other options
  1. Standard angiography
  2. CT angiography
  3. Magnetic resonance angiography
References
1. Hirsch (2002) Lecture, Fairview Lakes RMC

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 6/1/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.