A blood pressure difference between arms can be caused by:

1. Subclavian Artery Stenosis: Narrowing of the subclavian artery, often due to atherosclerosis, reducing blood flow to one arm.
2. Aortic Dissection: A tear in the aorta’s inner layer, which can disrupt blood flow to one arm, especially if the dissection involves the ascending aorta or arch.
3. Coarctation of the Aorta: A congenital narrowing of the aorta, potentially affecting blood pressure distribution.
4. Peripheral Artery Disease: Blockages or narrowing in arm arteries, reducing pressure on the affected side.
5. Thoracic Outlet Syndrome: Compression of blood vessels or nerves in the shoulder area, impacting blood flow.
6. Normal Variation: Small differences (less than 10-15 mmHg) can be normal, but larger gaps may indicate pathology.
7. Takayasu’s Arteritis: A rare inflammatory condition affecting large arteries, including those supplying the arms.
8. Measurement Error: Incorrect cuff size, arm position, or device calibration can cause false differences.

A difference greater than 15 mmHg systolic may warrant investigation, especially if accompanied by symptoms like arm pain, weakness, or pulse discrepancies. Consult a healthcare provider for evaluation, which may include imaging (e.g., ultrasound, CT, or MRI).

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