A 24-year-old male has had two syncopal episodes in the last 3 years, both during exercise of the right arm. What is the likely cause?

A 24-year-old male has had two syncopal episodes in the last 3 years, both during exercise of the right arm. What is the likely cause?

• A. Orthostatic Hypotension
• B. Subclavian Steal Syndrome
• C. Vasovagal Syncope
• D. Myocardial Ischemia

Answer: (B)

Exertional syncope limited to the use of one arm points to a steal phenomenon where blood flow to the brain is diverted to the exercising limb. If the proximal subclavian artery on the right is narrowed or occluded, blood can be drawn retrograde from the right vertebral artery to supply the arm during activity. This shunts blood away from the vertebrobasilar circulation, reducing cerebral perfusion at times of increased demand and causing syncope or dizziness during arm exercise. You may also notice a difference in blood pressure or pulse between arms, with weaker or absent pulses on the affected side. This pattern fits Subclavian Steal Syndrome best. Orthostatic hypotension would cause fainting with position changes rather than arm-specific exertion. Vasovagal syncope is typically triggered by other stimuli and has a broader prodrome, not tied to unilateral arm exercise. Myocardial ischemia is unlikely in a young healthy individual and would more often present with chest pain or ECG changes rather than arm-exercise–specific syncope.

Exertional syncope limited to the use of one arm points to a steal phenomenon where blood flow to the brain is diverted to the exercising limb. If the proximal subclavian artery on the right is narrowed or occluded, blood can be drawn retrograde from the right vertebral artery to supply the arm during activity. This shunts blood away from the vertebrobasilar circulation, reducing cerebral perfusion at times of increased demand and causing syncope or dizziness during arm exercise. You may also notice a difference in blood pressure or pulse between arms, with weaker or absent pulses on the affected side.

This pattern fits Subclavian Steal Syndrome best. Orthostatic hypotension would cause fainting with position changes rather than arm-specific exertion. Vasovagal syncope is typically triggered by other stimuli and has a broader prodrome, not tied to unilateral arm exercise. Myocardial ischemia is unlikely in a young healthy individual and would more often present with chest pain or ECG changes rather than arm-exercise–specific syncope.