Subclavian artery steal syndrome occurs in 90% of cases on the left side and presents with low blood pressure on the affected side. The patient’s upper extremity blood pressure is reduced on the affected side, with a difference in systolic blood pressure between the two upper extremities of 20 to 70 mmHg in most cases, and up to 150 mmHg in some cases. the radial artery on the affected side is mostly sluggish, diminished or absent, and in some cases the brachial or subclavian artery pulses are also diminished or absent. A systolic vascular murmur in the supraclavicular region can be heard in most cases and is aggravated by movement of the affected limb.
In addition, patients will also present with symptoms of ischaemia in the vertebrobasilar artery and upper limbs, such as vertigo, light limb paralysis and visual disturbances in the former, and inflexibility, abnormal sensation and painful weakness in the latter, which need to be analysed in conjunction with the patient’s multiple symptoms.