What is the significance of a difference in blood pressure readings between both arms, also known as bilateral blood pressure discrepancy?

From the Guidelines

A difference in blood pressure readings between arms of more than 10 mmHg is a significant finding that may indicate underlying vascular problems and is associated with an increased risk of cardiovascular disease, as recommended by the 2024 ESC guidelines for the management of elevated blood pressure and hypertension 1.

Key Points to Consider

• A small variation (less than 10 mmHg) in systolic pressure between arms is generally not concerning, but a consistent difference of 10-15 mmHg or more may indicate underlying vascular problems such as peripheral artery disease, atherosclerosis, or aortic dissection.
• The 2024 ESC guidelines recommend measuring blood pressure in both arms at least at the first visit, and if a between-arm difference of >10 mmHg in systolic BP is recorded, all subsequent BP readings should use the arm with the higher BP reading 1.
• The 2020 International Society of Hypertension global hypertension practice guidelines also recommend measuring BP in both arms, preferably simultaneously, and using the arm with the higher BP if there is a consistent difference between arms >10 mm Hg in repeated measurements 1.
• When measuring blood pressure at home, it's good practice to check both arms initially and then continue monitoring with the arm that shows the higher reading, using a properly sized cuff and following standard measurement techniques.

Recommendations for Clinical Practice

• Measure blood pressure in both arms at the first visit to detect any significant differences.
• If a difference of more than 10 mmHg is found, use the arm with the higher reading for all subsequent measurements.
• Consider further investigation if the difference is more than 20 mmHg, as recommended by the 2020 International Society of Hypertension global hypertension practice guidelines 1.
• Emphasize the importance of accurate blood pressure measurement techniques, including using a validated and calibrated device, and following standard measurement protocols, as recommended by the 2024 ESC guidelines 1.

From the Research

Significance of Bilateral Blood Pressure Discrepancy

• A difference in blood pressure readings between both arms, also known as bilateral blood pressure discrepancy, is a significant clinical finding that can have implications for diagnosis and management of hypertension 2, 3, 4, 5, 6.
• Studies have shown that inter-arm differences in blood pressure are common, with significant differences found in 20-30% of patients 3, 4.
• The prevalence of inter-arm differences varies widely between reports, and is correlated with the underlying cardiovascular risk of the population studied 6.

Clinical Implications

• Failure to determine inter-arm blood pressure differences can lead to erroneous clinical decisions, including misdiagnosis of hypertension 2.
• A difference in systolic blood pressure of 10 mmHg or more between arms has been associated with peripheral vascular disease, cerebrovascular disease, and increased cardiovascular mortality 5.
• Inter-arm differences in blood pressure are also associated with other signs of vascular disease, such as peripheral arterial disease 6.

Measurement and Detection

• Guidelines recommend measuring blood pressure in both arms at the first visit, and recording the higher blood pressure reading 2, 4.
• The method of measurement used can affect the prevalence of inter-arm differences, with simultaneous measurements using automated devices providing more accurate results 3.
• Current best practice for detection and measurement of inter-arm differences involves using standardized protocols and equipment to minimize errors and ensure accurate readings 6.

Associations and Risk Factors

• Inter-arm differences in blood pressure have been associated with increased cardiovascular morbidity and mortality, as well as all-cause mortality 5, 6.
• Competing aetiological explanations for inter-arm differences include subclavian stenosis, peripheral vascular disease, and other vascular conditions 5.
• Further research is needed to fully understand the significance and implications of inter-arm blood pressure discrepancies, including the development of standardized protocols for measurement and detection 6.