From the Guidelines
The normal value for an ankle-brachial index (ABI) is between 1.0 and 1.4. This measurement represents the ratio of blood pressure at the ankle compared to the blood pressure in the arm (brachial artery) 1. An ABI within this normal range indicates healthy arterial circulation to the lower extremities.
Key Points to Consider
- Values below 0.9 suggest peripheral artery disease (PAD), with lower values indicating more severe disease: mild PAD (0.7-0.9), moderate PAD (0.4-0.69), and severe PAD (<0.4) 1.
- Values above 1.4 may indicate calcified or non-compressible arteries, often seen in patients with diabetes or end-stage renal disease 1.
- The ABI is a simple, non-invasive test that provides valuable information about arterial blood flow to the legs and feet 1.
- It's particularly useful for diagnosing PAD, especially in patients with risk factors such as smoking, diabetes, hypertension, or high cholesterol, even before symptoms like claudication (leg pain with walking) develop 1.
Diagnostic Considerations
- In cases of an ABI >0.90 and clinical suspicion of PAD, post-exercise ABI measurements should be considered, along with imaging studies (preferably by treadmill) 1.
- A post-exercise ABI decrease of >20% may serve as a PAD diagnostic criterion 1.
- For patients with an ABI >1.4, a toe-brachial index (TBI) can be used to evaluate for PAD, with a TBI of ≤0.70 considered abnormal 1.
From the Research
Ankle Brachial Index Values
- Normal cut-off values for ABI are between 0.9 and 1.4 2
- An abnormal ankle-brachial index, below 0.9, is a powerful independent marker of cardiovascular risk 2
- ABI values over 1.3-1.4 correlate with major adverse cardiovascular events 2
ABI and Cardiovascular Disease
- The ankle-brachial index can be considered a generalized atherosclerotic predictor, identifying patients at high risk for developing cardio- or cerebrovascular events 2
- Adding the ABI to the Framingham Risk Score probably has limited value for predicting coronary artery disease or cardiovascular disease 3
- Abnormal ABI values show a U-shaped relationship with mortality, serving as strong predictors of cardiovascular and all-cause mortality in patients with chronic kidney disease 4