Ankle-Brachial Index Measurement and Interpretation

Introduction to Ankle-Brachial Index

• The American College of Cardiology recommends measuring the ankle-brachial index (ABI) using a standard sphygmomanometer and stethoscope, without the need for a Doppler ultrasound device, although this method has limitations in sensitivity that must be considered 1, 2, 3

Methods for Measuring Ankle-Brachial Index

• The ABI with Doppler is the most commonly used method in clinical settings for screening and detecting peripheral arterial disease (PAD), calculated as the systolic blood pressure at the ankle divided by the systolic blood pressure at the arm with the patient at rest 1, 2
• A value <0.9 is considered abnormal and defines PAD, while values >1.40 indicate non-compressible arteries (typically due to medial arterial calcification) 2, 3

Interpretation of Ankle-Brachial Index Results

• The American College of Cardiology states that an ABI ≤0.90 is abnormal, confirming PAD 2, 3, 4
• An ABI of 0.91-0.99 is considered borderline, and a stress test with ABI may be considered 3, 5
• An ABI of 1.00-1.40 is considered normal 3, 4
• An ABI >1.40 is considered non-compressible, requiring a toe-brachial index (TBI) 3, 4, 5

Special Considerations

• The American College of Cardiology recommends measuring ABI in patients ≥65 years old, or ≥50 years old with risk factors (smoking, diabetes, hypertension, hyperlipidemia) 3, 4
• If Doppler is not available, a stethoscope or oscillometric device may be used 3, 4
• If the patient has symptoms of claudication with a normal or borderline ABI, a stress test with ABI on a treadmill may be performed (Class I, Level of Evidence B) 3, 5