Inter‑Arm Blood Pressure Difference as a High‑Risk Marker for Acute Aortic Dissection

Diagnostic Significance

A systolic blood‑pressure difference of ≥ 20 mm Hg between arms is a high‑risk clinical marker that mandates immediate advanced imaging with CT angiography in patients with suspected acute aortic syndrome. American Heart Association recommendation. 1
An inter‑arm systolic pressure difference of ≥ 15–20 mm Hg is considered definitively abnormal and, in the acute setting, strongly suggests either subclavian/innominate artery stenosis or an aortic dissection. American College of Cardiology guidance. 2, 3

The blood‑pressure differential is incorporated as a high‑risk examination feature in the Aortic Dissection Detection (ADD) risk score, alongside pulse deficit, focal neurologic deficit, new aortic‑insufficiency murmur, and hypotension/shock. American College of Emergency Physicians (ADD score development). 4, 5
Calculation of the ADD risk score requires assessment of three domains—high‑risk conditions (e.g., Marfan syndrome, known thoracic aneurysm), high‑risk pain features (abrupt onset, severe intensity, tearing quality), and high‑risk examination features (including the inter‑arm BP difference). American College of Emergency Physicians. 4

Both arms must be measured during the initial evaluation of any patient with suspected acute aortic syndrome to detect a potentially lethal inter‑arm pressure gradient. American Heart Association protocol. 1

When a significant inter‑arm BP difference is identified in a patient with acute chest, back, or abdominal pain, the first imaging step is CT angiography of the chest, owing to its wide availability, rapid acquisition, and detailed anatomic visualization. American Heart Association imaging algorithm. 1
If CT is contraindicated or unavailable, transesophageal echocardiography (TEE) or magnetic resonance imaging (MRI) are acceptable alternative modalities. American Heart Association. 1
Plain chest radiography should not be relied upon to exclude aortic dissection because of its low sensitivity and specificity. American College of Emergency Physicians recommendation. 4
A zero ADD score does not safely exclude dissection; prevalence remains 4.3–5.9 % in such patients, underscoring the need for imaging when clinical suspicion persists. American College of Emergency Physicians data. 4

A blood pressure difference of >20 mmHg between arms is a significant clinical sign of aortic dissection and should prompt immediate further evaluation, especially when combined with other clinical features of dissection, according to the European Society of Cardiology 6, 7
Measuring blood pressure in both arms is essential to detect this important clinical sign in patients with suspected aortic dissection, as recommended by the European Heart Journal 6, 8
Blood pressure differentials are part of the clinical triad for aortic dissection, along with aortic pain and mediastinal/aortic widening on chest radiograph, as noted by the American College of Emergency Physicians 7

When a significant inter-arm difference is detected, the arm with the higher reading should be used for subsequent blood pressure monitoring, as suggested by the European Heart Journal 6, 9, 10
Pressure measurement on both arms is important to rule out pseudo-hypotension due to obstruction of an aortic arch branch, according to the European Society of Cardiology 6
In unstable patients with suspected aortic dissection, an arterial line should be placed in the right radial artery for invasive blood pressure monitoring, as recommended by the European Heart Journal 6

Sequential arm measurement is considered sufficiently reliable, though simultaneous measurement devices exist, as noted by the European Heart Journal 9, 10
Measurement technique is crucial - use appropriately sized cuffs and position both arms at heart level, as suggested by the European Society of Cardiology 11, 12

Once aortic dissection is diagnosed, aggressive blood pressure control is essential, with target systolic BP between 100-120 mmHg, as recommended by the European Society of Cardiology 6
Beta-blockers are the first-line agents for blood pressure control in aortic dissection due to their effect on reducing the force of left ventricular ejection, according to the European Heart Journal 6