Ankle–Brachial Pressure Index (ABPI)

Ankle–Brachial Pressure Index (ABPI)

Definition

Ankle–Brachial Pressure Index (ABPI), also called Ankle–Brachial Index (ABI), is a simple, non-invasive bedside test that compares systolic blood pressure at the ankle with systolic blood pressure at the brachial artery to assess lower-limb arterial perfusion.

---

Principle

Peripheral arterial disease (PAD) causes reduced systolic pressure distal to arterial stenosis or occlusion. Comparing ankle pressure with arm pressure provides an objective estimate of arterial flow to the legs.

---

Formula

ABPI =

Highest ankle systolic pressure (dorsalis pedis or posterior tibial) ÷ Highest brachial systolic pressure

Measured separately for each leg.

---

Methods of Measuring ABPI

1. Doppler-Assisted ABPI (Gold Standard)

Equipment

Hand-held Doppler (8–10 MHz)

Sphygmomanometer cuffs (appropriate size)

Steps

1. Patient rests supine for ≥10 minutes

2. Measure systolic BP in both brachial arteries using Doppler

3. Measure systolic BP at:

Dorsalis pedis artery

Posterior tibial artery

4. Use the higher ankle pressure and higher brachial pressure for calculation

Advantages

Most accurate bedside method

Widely recommended in guidelines

Limitations

Requires operator skill

Time-consuming in busy clinics

---

2. Automated Oscillometric ABPI

Description

Automated BP devices measure arm and ankle pressures simultaneously or sequentially

Advantages

Quick

Minimal training required

Limitations

Less accurate in:

Diabetes

Chronic kidney disease

Severe PAD

May underestimate disease severity

---

3. Toe–Brachial Index (TBI) (When ABPI is Unreliable)

Indications

Non-compressible arteries (ABPI >1.3)

Diabetes mellitus

Medial arterial calcification

Normal TBI

≥0.7

---

Interpretation of ABPI

ABPI Value Interpretation

1.00 – 1.30 Normal

0.91 – 0.99 Borderline

0.41 – 0.90 Mild–Moderate PAD

≤0.40 Severe PAD

>1.30 Non-compressible arteries

---

Clinical Uses of ABPI

1. Diagnosis of Peripheral Arterial Disease

Detects symptomatic and asymptomatic PAD

Correlates with angiographic disease severity

2. Cardiovascular Risk Stratification

Low ABPI is an independent predictor of:

Myocardial infarction

Stroke

Cardiovascular mortality

3. Assessment of Leg Pain

Differentiates vascular claudication from:

Neurogenic claudication

Musculoskeletal pain

4. Wound and Ulcer Assessment

Guides safety of compression therapy in venous ulcers

Predicts wound healing potential

5. Pre- and Post-Revascularization Evaluation

Baseline assessment before intervention

Objective follow-up after angioplasty or surgery

---

Contraindications / Cautions

Severe leg pain or acute limb ischemia (do not delay urgent care)

Incorrect cuff size can produce false results

Calcified arteries may falsely elevate ABPI

---

Factors Affecting Accuracy

Diabetes mellitus

Chronic kidney disease

Advanced age

Edema

Improper patient positioning

---

Key Points

ABPI is a rapid, inexpensive, and non-invasive test

Doppler-assisted method is preferred for accuracy

Abnormal ABPI indicates both limb ischemia and systemic atherosclerosis

High values (>1.3) are not normal and require alternative assessment

---

For more cardiology infographics and articles, visit: drmusmanjaved.com