What is normal ankle blood pressure in relation to brachial blood pressure?

From the Guidelines

Normal ankle blood pressure is typically slightly higher than at the brachial artery, with systolic pressure about 10-15 mmHg higher in the ankle compared to the arm, and an ankle-brachial index (ABI) between 1.0 and 1.4 is considered normal. In a healthy individual, ankle systolic blood pressure usually ranges from 130-150 mmHg, while diastolic pressure remains similar to brachial readings (approximately 70-90 mmHg) 1. This difference occurs due to the phenomenon of pulse wave amplification, where pressure waves increase in amplitude as they travel away from the heart through progressively stiffer and narrower arteries.

Key Points to Consider

• The ABI is a low-cost, easy, and largely used tool for PAD diagnosis and surveillance, with a sensitivity of 68%–84% and a specificity of 84%–99% for PAD diagnosis 1.
• An ABI ≤0.90 confirms PAD, while an ABI >1.40 indicates non-compressible arteries 1.
• When measuring ankle blood pressure, the patient should be supine for at least 5 minutes before measurement, and a properly sized cuff should be placed just above the ankle with the Doppler probe positioned over the posterior tibial or dorsalis pedis artery to detect blood flow 1.
• The toe-brachial index (TBI) can be used to establish the lower extremity PAD diagnosis in patients in whom the ABI test is not reliable due to noncompressible vessels, with a normal TBI being ≥0.70 1.

Measurement Protocol

• The patient should be at rest for 5 to 10 minutes in the supine position before measurement 1.
• A properly sized cuff should be placed just above the ankle, with the Doppler probe positioned over the posterior tibial or dorsalis pedis artery to detect blood flow 1.
• The ABI should be measured in both legs in all new patients with PAD of any severity to confirm the diagnosis of lower extremity PAD and establish a baseline 1.

From the Research

Ankle Blood Pressure in Relation to Brachial Blood Pressure

• The normal range for ankle systolic blood pressure (SBP) is suggested to be 100-165 mmHg in young subjects and 110-170 mmHg in middle-elderly subjects, based on a study that measured supine BP of four limbs using automatic BP measurement devices 2.
• Ankle SBP is significantly higher than arm SBP, with a mean difference of 13-20 mmHg depending on age group 2.
• The ankle-brachial index (ABI) is a useful tool for diagnosing peripheral arterial disease (PAD), with an ABI ≤ 0.90 indicating PAD 3.
• ABI values between 0.9 and 1.4 are considered normal, while values below 0.9 or above 1.3-1.4 are associated with increased cardiovascular risk 4, 5.
• Elevated ankle blood pressure (> 175 mmHg) is an independent predictor of cardiovascular and total mortality, even in individuals with normal resting brachial blood pressure 6.

Key Findings

• Ankle blood pressure has an independent value as a marker of arterial stiffness or subclinical atherosclerosis and a risk of future mortality 6.
• Screening for PAD with the ankle-brachial index can increase the percentage of polyvascular patients identified and provide valuable information on overall cardiovascular risk 5.
• The diagnostic accuracy of ABI ≤ 0.90 for PAD diagnosis is high, with a pooled sensitivity and specificity of 75% and 86%, respectively 3.