What is the interpretation of Ankle-Brachial Index (ABI) results with high values, including left arm 140, right arm 140, right leg 138, and left leg 140?

Interpretation of Ankle-Brachial Index Results

Your ABI values (left arm 140, right arm 140, right leg 138, left leg 140) indicate noncompressible arteries, which is associated with increased cardiovascular risk and requires further evaluation.

Understanding Your ABI Results

• ABI is calculated by dividing ankle systolic pressure by brachial systolic pressure 1, 2
• Normal ABI values range from 0.91 to 1.40 1
• Your values appear to be raw pressure measurements in mmHg, which would calculate to ABI values of approximately 0.99 (right leg) and 1.0 (left leg) if using the higher arm pressure as denominator 1
• However, if these are actual ABI values (not raw pressures), they would be classified as noncompressible arteries (ABI >1.40) 1

Clinical Significance of Noncompressible Arteries

• ABI values >1.40 indicate noncompressible arteries, often due to arterial calcification 1, 2
• Noncompressible arteries are commonly seen in patients with diabetes mellitus and/or advanced chronic kidney disease 1
• Patients with noncompressible ABIs have significantly higher rates of cardiovascular mortality compared to those with normal ABIs 3, 4
• One study found 21.7% cardiovascular mortality at 2 years in patients with noncompressible arteries compared to 0% in those with normal ABIs 3

Recommended Next Steps

• Additional vascular imaging is recommended when ABI values are noncompressible and clinical suspicion of peripheral artery disease (PAD) exists 1
• Consider toe-brachial index (TBI) measurement, as digital arteries are rarely noncompressible 1
• A TBI ≤0.70 is considered abnormal and allows for diagnosis of PAD in patients with noncompressible ABIs 1
• Comprehensive cardiovascular risk assessment is warranted, including evaluation for coronary and carotid artery disease 3, 5

Interpreting Individual Vessel Measurements

• When evaluating for PAD diagnosis, using the higher ankle pressure is preferred to minimize overdiagnosis 1, 2
• For cardiovascular risk assessment, using the lower ankle pressure identifies more individuals at risk 1, 2
• Discordant values between different ankle arteries (when some indicate PAD and others don't) are associated with increased risk of myocardial infarction, stroke, and all-cause mortality 6

Important Considerations

• Body position affects ABI measurements - patients should be lying flat with head and heels fully supported during measurement 1
• The relationship between ABI and mortality follows a reverse J-shaped curve, with lowest risk in the 1.11-1.40 range and increased risk with both low and high values 1, 2
• Noncompressible arteries in patients with critical limb ischemia are associated with higher rates of mortality, major adverse cardiovascular events, and major amputation 4
• Serial ABI measurements may provide more accurate assessment than a single measurement 2

Algorithm for Management

1. Confirm whether values are raw pressures or calculated ABIs
2. If noncompressible arteries are confirmed (ABI >1.40):
   • Perform toe-brachial index measurement 1
   • Consider vascular imaging (duplex ultrasound, CT angiography, or MR angiography) 1
   • Evaluate for cardiovascular risk factors and comorbidities 3, 5
   • Implement appropriate cardiovascular risk reduction strategies 2
3. If values represent raw pressures, calculate actual ABIs and interpret accordingly