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Difficulty: HardPhysical Examination Findings

A 62-year-old woman with a history of hypertension, hyperlipidemia, and peripheral artery disease is evaluated in the outpatient clinic for recurrent episodes of dizziness. Over the past three months, she has experienced several brief spells of room-spinning vertigo, blurred vision, and left arm heaviness. She notes that these episodes most reliably occur when she is blow-drying her hair or reaching up to hang laundry on an overhead line. She denies hearing loss, tinnitus, palpitations, or loss of consciousness. Current medications include amlodipine, atorvastatin, and low-dose aspirin. She is currently resting comfortably in the exam room. Based on the most likely diagnosis, which of the following physical examination findings are expected in this patient? (Select 2 answers)

  1. A systolic blood pressure difference of greater than 15 mm Hg between the left and right armsAnswer
  2. A harsh systolic bruit auscultated over the left supraclavicular fossaAnswer
  3. C
    A delayed and diminished carotid arterial upstroke on the left side
  4. D
    Torsional nystagmus elicited by rapidly transitioning the patient from a sitting to a supine position
  5. E
    A drop in systolic blood pressure of greater than 20 mm Hg within three minutes of standing

Answer

A systolic blood pressure difference of greater than 15 mm Hg between the left and right arms, and a harsh systolic bruit auscultated over the left supraclavicular fossa.
This patient's presentation of vertebrobasilar insufficiency (vertigo, blurred vision) triggered by upper extremity exertion is highly characteristic of Subclavian Steal Syndrome. This condition most commonly occurs due to severe atherosclerosis and stenosis of the left subclavian artery proximal to the origin of the vertebral artery. When the left arm is exercised, the increased vascular demand causes blood to flow retrogradely down the left vertebral artery to supply the arm, 'stealing' blood from the vertebrobasilar circulation. Physical examination typically reveals signs of decreased perfusion to the affected arm, most notably a systolic blood pressure difference of >15 mm Hg between the arms, as well as a systolic bruit over the supraclavicular fossa due to turbulent flow through the stenotic subclavian artery.

Step-by-Step Solution

1
Analyze the patient's symptoms and triggers.
The patient experiences vertebrobasilar insufficiency (vertigo, blurred vision) and arm claudication specifically triggered by upper extremity exertion.
Identifying the exertional trigger points toward a vascular steal phenomenon rather than primary vestibular or generalized orthostatic etiologies.
2
Formulate the most likely diagnosis.
The clinical picture is classic for Subclavian Steal Syndrome, typically caused by severe stenosis of the left subclavian artery proximal to the vertebral artery origin.
Arm exercise causes vasodilation, dropping resistance and causing blood to flow retrogradely down the vertebral artery, 'stealing' from the brainstem.
3
Deduce the expected physical examination findings based on the anatomical lesion.
The proximal subclavian stenosis causes a pressure drop in the affected arm and turbulent flow at the site of the lesion.
This hemodynamically translates to a significant inter-arm blood pressure discrepancy and a local supraclavicular bruit.

Key Concept

Physical examination findings in Subclavian Steal Syndrome
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Topics

Physical Examination Findings

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