vascular general-medicine cardiology

Ankle-Brachial Index (ABI)

Diagnoses and grades severity of peripheral arterial disease (PAD). ABI = ankle systolic BP / brachial systolic BP. Predicts cardiovascular risk.

Score interpretation

Normal ABI (1.00–1.40) 0

ABI 1.00–1.40 is normal (AHA 2012).

→ PAD unlikely at rest. With exertional leg symptoms: post-exercise ABI (ACC/AHA 2016). In diabetes a normal ABI does not exclude PAD — toe pressure / toe-brachial index (NICE CG147).

Borderline ABI (0.91–0.99) 1

ABI 0.91–0.99 is borderline (AHA 2012).

→ Cardiovascular risk-factor management; post-exercise ABI if exertional symptoms; repeat if symptoms progress.

PAD (ABI 0.50–0.90) 2

ABI ≤ 0.90 is diagnostic of PAD (AHA 2012).

→ Secondary prevention (antiplatelet, statin, BP control, smoking cessation); supervised exercise programme for claudication (NICE CG147); vascular referral if lifestyle-limiting or the diagnosis is in doubt.

Severe PAD (ABI < 0.50) 3

ABI < 0.5 indicates severe arterial disease (ESVS 2015).

→ Urgent vascular referral; look for rest pain or tissue loss; compression bandaging or hosiery is contraindicated.

Non-Compressible Arteries (ABI > 1.40) 4

Calcified arteries: the ABI is unreliable (AHA 2012).

→ Toe-brachial index (abnormal ≤ 0.70), toe pressure or duplex to assess for PAD.

Rest Pain or Tissue Loss — Suspected CLTI 5

Ischaemic rest pain, ulceration or gangrene suggests chronic limb-threatening ischaemia whatever the ABI — calcified arteries can give a normal or high ABI (Global Vascular Guidelines 2019).

→ Urgent vascular surgery referral; toe pressure / TcPO2 and duplex; WIfI staging; wound care.

Interpretation bands for the Ankle-Brachial Index. Apply clinical judgement and local guidance.

References

Curated clinical cross-links plus same-class fallbacks.

Drugs

Pathways

Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.

Score interpretation

References

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