subclavian steal syndrome

Subclavian steal syndrome and subclavian steal phenomenon both result from severe proximal subclavian artery stenosis or occlusion resulting in retrograde flow in the ipsilateral vertebral artery.

Terminology

Subclavian steal phenomenon refers to steno-occlusive disease of the proximal subclavian artery with retrograde flow in the ipsilateral vertebral artery.

Subclavian steal syndrome is the same as subclavian steal phenomenon with the addition of cerebral ischemic symptoms.

Epidemiology

There is an increased incidence with age and the greater male predilection with a M:F ratio of 2:1. It is commoner on the left side with L:R ratio of ~3:1.

Clinical presentation

• ipsilateral upper limb
  • weak or absent pulse
  • decreased systolic blood pressure in the affected side; systolic blood pressure difference between the brachial arteries are more than 20 mmHg
  • arm claudication (rare due to collateral perfusion)
• neurological (exacerbated by arm exercise)
  • dizziness/vertigo/syncope
  • ataxia
  • visual changes
  • dysarthria
  • weakness/sensory disturbances

Pathology

Subclavian artery steno-occlusive disease results in decreased perfusion to the ipsilateral arm and hand. Subclavian artery branches distal to the obstruction act as collateral pathways to maintain upper limb perfusion.

If the level of stenosis or occlusion is proximal to the vertebral artery, then reversal of flow in the vertebral artery may occur, thereby stealing blood from the posterior circulation. When the upper limb is exercised, blood is diverted away from the brain to the arm. Whether or not this steal phenomenon causes cerebral ischemic symptoms depends on the adequacy of intracranial collateral circulation, especially the posterior communicating arteries. Patients with adequate intracranial collateral circulation are usually asymptomatic; 80% of symptomatic patients have lesions elsewhere in the intracranial or extracranial cerebral circulation.

Patients in whom the left vertebral artery arises directly from the aortic arch are protected from subclavian steal syndrome on the left.

Etiology

• atherosclerosis: ~95%
• vasculitides, e.g. Takayasu arteritis, radiation
• thoracic aortic dissection
• Blalock-Taussig shunt
• congenital 
  • interrupted aortic arch
  • preductal aortic coarctation
  • right aortic arch with isolated left subclavian

Radiographic features

Ultrasound

• retrograde flow in the ipsilateral vertebral artery
• early changes prior to reversal of flow: decreased velocity, biphasic flow (in the vertebral artery), including bunny waveform sign
• changes can be augmented with arm exercise or inflation of BP cuff above systolic pressure
• proximal subclavian artery usually cannot be seen well enough to assess
• distal subclavian artery shows parvus-tardus waveform and monophasic waveform

CT

• subclavian artery stenosis or occlusion is easily identified
• delayed enhancement of ipsilateral vertebral artery
• unable to determine the direction of flow in the vertebral artery
• other intracranial or extracranial cerebral vascular lesions can be identified

MR

• subclavian artery stenosis or occlusion easily identified
• delayed enhancement of ipsilateral vertebral artery
• retrograde direction of flow in the ipsilateral vertebral artery
• other intracranial or extracranial cerebral vascular lesions can also be identified

DSA

• performed at the time of endovascular intervention
• subclavian artery stenosis or occlusion easily identified
• delayed filling of ipsilateral vertebral artery (which fills retrogradely)
• other intracranial or extracranial cerebral vascular lesions can also be identified

Treatment and prognosis

• endovascular: angioplasty +/- stenting
• surgical: bypass surgery

Siehe auch:

• Vaskulitis
• Takayasu-Arteriitis
• Atherosklerose
• Blalock-Taussig shunt
• subclavian artery occlusion
• Subclavian-Steal-Syndrom bei Arteria lusoria
• Angeborene Subclavian-Steal-Sequenz
• präduktale Aortenisthmusstenose
• Subclaviastenose
• Atresie der Aorta

und weiter:

• rechts descendierende Aorta
• doppler findings in partial subclavian steal syndrome
• vaskuläre Syndrome