What is the significance of a blood pressure difference between arms, with a reading of 156/76 mmHg in the left arm and 98/72 mmHg in the right arm?

Urgent Vascular Evaluation Required for 58 mmHg Inter-Arm Blood Pressure Difference

This 58 mmHg systolic blood pressure difference between arms (156/76 left vs 98/72 right) is highly abnormal and strongly suggests serious vascular pathology requiring immediate further evaluation for conditions such as subclavian artery stenosis, aortic dissection, or large vessel vasculitis. 1

Why This Finding is Critical

• Normal inter-arm differences are minimal, with mean systolic differences of only 1-3 mmHg in healthy individuals 1, 2
• Differences ≥20 mmHg are strongly suggestive of significant vascular pathology and require urgent evaluation 1, 2, 3
• Your patient's 58 mmHg difference far exceeds this threshold and represents a medical emergency requiring immediate action 1

First Step: Confirm the Finding

Before proceeding with urgent workup, you must rule out measurement error:

• Repeat measurements simultaneously in both arms using proper technique to confirm this is not artifactual 1, 2
• Ensure both arms are positioned at heart level during measurement, as arm position errors can create artificial differences of 10 mmHg or more (2 mmHg for every inch above or below heart level) 4, 2, 5
• Use appropriately sized cuffs for each arm and the same measurement technique 1, 2
• Support both arms properly rather than having the patient hold them up, as isometric muscle contraction raises blood pressure 4

Most Likely Diagnoses to Consider

Subclavian Artery Stenosis or Occlusion

• Upper extremity arterial obstruction is the most common cause of large inter-arm differences 1, 2
• The lower reading (right arm at 98/72) suggests significant stenosis or occlusion of the right subclavian artery 1

Aortic Dissection (EMERGENCY)

• A blood pressure difference >20 mmHg between arms is a significant clinical sign of aortic dissection, especially when combined with chest pain, back pain, syncope, or neurological symptoms 3
• This is part of the clinical triad: aortic pain, blood pressure differential, and mediastinal widening on chest X-ray 3

Other Large Vessel Pathology

• Takayasu arteritis or other large vessel vasculitis 1
• Aortic coarctation 1, 2

Immediate Clinical Assessment Required

Perform a focused vascular examination immediately:

• Check for diminished or delayed pulses in the right arm compared to the left 1
• Listen for bruits over the right subclavian and carotid arteries 1
• Assess for signs of peripheral vascular disease in other vascular beds 1
• Evaluate for symptoms of aortic dissection: chest pain, back pain, syncope, neurological deficits, or acute limb ischemia 3

Urgent Diagnostic Workup

If aortic dissection is suspected (acute presentation with pain, syncope, or neurological symptoms):

• Immediate emergency evaluation is warranted with stat CT angiography or transesophageal echocardiography 1, 3
• Place an arterial line in the left radial artery (the arm with higher pressure) for invasive monitoring if the patient is unstable 3

If presentation is subacute without dissection symptoms:

• Order duplex ultrasound of subclavian and axillary arteries as initial imaging 1
• Consider CT angiography or MR angiography to evaluate the aortic arch and great vessels 1

Management Implications

• Use the left arm (higher reading of 156/76) for all subsequent blood pressure monitoring to avoid underestimating blood pressure and missing hypertension 1, 2, 3
• Refer urgently to vascular surgery or cardiology for definitive evaluation and management 1
• If subclavian stenosis is confirmed, the patient needs evaluation for concomitant coronary artery disease, as this represents systemic atherosclerosis 1

Critical Pitfalls to Avoid

• Do not dismiss this as measurement error without proper confirmation with repeat measurements 1, 2
• Do not delay evaluation thinking this represents normal variation—differences ≥20 mmHg are never normal 1, 2
• Do not use different cuff sizes or measurement techniques between arms when confirming the finding 1, 2
• Do not overlook acute aortic dissection, especially if any chest/back pain, syncope, or neurological symptoms are present 3