Differential Diagnosis for Blood Pressure Lower in One Arm Compared to the Other

• Single Most Likely Diagnosis

  • Atherosclerotic Subclavian Artery Stenosis: This condition, where the subclavian artery becomes narrowed due to atherosclerosis, is a common cause of a significant difference in blood pressure readings between the two arms. The stenosis can lead to reduced blood flow to the arm, resulting in lower blood pressure readings.

• Other Likely Diagnoses

  • Subclavian Artery Thrombosis: A blood clot in the subclavian artery can also reduce blood flow to the arm, leading to lower blood pressure readings.
  • Thoracic Outlet Syndrome: Compression of the subclavian artery or vein by the thoracic outlet (the space between the collarbone and first rib) can cause reduced blood flow and lower blood pressure in the affected arm.
  • Arterial Dissection or Aneurysm: Although less common, a dissection (tear in the artery wall) or an aneurysm (ballooning of the artery wall) in the subclavian artery can also lead to differential blood pressure readings.

• Do Not Miss Diagnoses

  • Aortic Dissection: A tear in the aorta's inner layer can lead to a false lumen and compromised blood flow to the subclavian artery, resulting in differential blood pressure readings. This is a medical emergency.
  • Takayasu Arteritis: A large vessel vasculitis that can cause stenosis or occlusion of the subclavian arteries, leading to differential blood pressure readings. Early diagnosis is crucial to prevent long-term complications.

• Rare Diagnoses

  • Coarctation of the Aorta: A congenital narrowing of the aorta that can lead to differential blood pressure readings, although it typically presents with hypertension in the arms and lower blood pressure in the legs.
  • Vasculitis (e.g., Giant Cell Arteritis, Polyarteritis Nodosa): Inflammatory conditions that can affect the subclavian arteries and lead to stenosis or occlusion, resulting in differential blood pressure readings.
  • Subclavian Steal Syndrome: A condition where there is reversal of blood flow in the vertebral artery due to significant stenosis or occlusion of the subclavian artery, which can lead to symptoms of vertebrobasilar insufficiency and differential blood pressure readings.