From the Guidelines
A significant difference in blood pressure between the left and right arms is most commonly caused by subclavian artery stenosis, which is usually resulting from atherosclerosis, as stated in the 2024 ESC guidelines for the management of peripheral arterial and aortic diseases 1. The primary causes of blood pressure differences between the left and right upper extremities include:
- Subclavian artery stenosis
- Aortic dissection
- Peripheral artery disease
- Large vessel vasculitis such as Takayasu's arteritis
- Anatomical variations like coarctation of the aorta or compression syndromes (thoracic outlet syndrome) Any blood pressure difference exceeding 15 mmHg between arms warrants medical evaluation, as it correlates with increased cardiovascular risk and may indicate underlying vascular disease requiring treatment, as mentioned in the 2012 American Heart Association scientific statement on the measurement and interpretation of the ankle-brachial index 1. The affected arm typically shows lower pressure readings due to reduced blood flow from the obstruction. It is essential to note that the 2024 ESC guidelines 1 provide the most recent and highest quality evidence on this topic, and therefore, their recommendations should be prioritized. Key points to consider:
- Subclavian artery stenosis is the most frequent cause of blood pressure differences between the left and right arms
- A blood pressure difference exceeding 15 mmHg between arms is a significant indicator of underlying vascular disease
- Medical evaluation is necessary to determine the underlying cause of the blood pressure difference and to provide appropriate treatment.
From the Research
Blood Pressure Differences in Upper Extremities
The difference in blood pressure between the left and right upper extremities can be attributed to several factors, including:
- Anatomical differences in the origin of the left and right subclavian arteries 2
- Subclavian artery stenosis, which can lead to reduced blood flow to the upper extremities 3, 4
- Thoracic outlet syndrome (TOS), which can cause compression of the subclavian artery and lead to differences in blood pressure between the two arms 5, 6
Causes of Blood Pressure Differences
Some specific causes of blood pressure differences between the left and right upper extremities include:
- Arterial thoracic outlet syndrome (aTOS), which can cause chronic findings such as pallor, arm claudication, or cool arm 5
- Subclavian artery stenosis, which can lead to symptomatic ischemia affecting the upper extremities 3
- Anatomic variants, such as differences in the origin of the left and right subclavian arteries, which can affect blood flow to the upper extremities 2, 4
Clinical Implications
It is essential for clinicians to be aware of the potential differences in blood pressure between the left and right upper extremities, as this can have significant clinical implications, including: