If a person has asymmetric brachial blood pressures, this can indicate carotid stenosis on which side?

Not necessarily: If the patient has carotid stenosis on one side, that same side can present with higher arm BP than the other arm. But other things can also cause asymmetric BP including thoracic outlet syndrome, subclavian steal syndrome, and coarctation of the aorta. Always take repeated BP measures over several occasions to see definitive pattern.

Subclavian stenosis: This would suggest subclavian or axillary artery stenosis not carotid.