Understanding Coronary Subclavian Steal Syndrome.

Dr. Zayed | Published : 21, May 2025.

Coronary Subclavian Steal Syndrome (CSSS) is rare but clinically significant condition that arises in patients with aorto-coronary bypass grafts, particularly when the internal mammary artery (IMA) is used as a conduit. It involves retrograde flow through the IMA graft, typically due to a hemodynamically significant stenosis or occlusion of the ipsilateral subclavian artery proximal to the origin of the graft.

LIMA TO LAD CABG

Etiology:

  • atherosclerosis
  • Narrowing, hardening of arteries due to plaque buildup
  • Takayasu disease (least common)
  • Chronic inflammation of aorta, large vessels
  • Giant cell arteritis
  • Blalock Taussig shunt
  • Surgical procedure to increase blood flow to lungs; tube placed between subclavian, pulmonary arteries
  • Thoracic aortic dissection
  • Thoracic outlet compression
  • Interrupted aortic arch
  • Congenital aortic coarctation

Pathophysiology

In CSSS, a proximal subclavian artery stenosis or occlusion leads to a pressure gradient that causes blood to flow retrogradely from the coronary circulation into the subclavian artery to perfuse the upper extremity. This results in myocardial ischemia, particularly during exertion of the ipsilateral arm.

Clinical Presentation

Patients presents with:

  • Angina pectoris, particularly precipitated by upper extremity exertion

  • Left arm claudication

  • Drop attacks/syncope manifest as dizziness, diplopia, nystagmus, tinnitus, or even hearing loss.

  • Blood pressure discrepancy between arms (>15–20 mmHg)

In post-coronary artery bypass graft (CABG) patients, particularly those with left internal mammary artery (LIMA) grafts, unexplained angina or ischemic symptoms should prompt suspicion.

However, even when flow reversal in the vertebral system is observed, ischemic neurological events may be attributable to other processes, such as thromboembolism or embolization of atherosclerotic material from proximal subclavian disease, and is not necessarily related to a steal phenomenon.

Diagnostic Modalities

  • Doppler Ultrasonography: Can detect reversed flow in the vertebral or IMA.
  • Computed Tomography Angiography (CTA) or Magnetic Resonance Angiography (MRA): Evaluate stenosis of the subclavian artery and patency of grafts.
  • Coronary Angiography with selective IMA injection: Confirms retrograde flow from LIMA into the subclavian artery.
  • Ankle-Brachial Index and inter-arm blood pressure comparison.

Management

Treatment is aimed at revascularizing the subclavian artery:

  • Percutaneous Transluminal Angioplasty (PTA) with stenting is first-line in most cases.

  • Surgical bypass (e.g., carotid-subclavian bypass) may be considered in complex or failed percutaneous interventions.

Concurrent optimization of cardiovascular risk factors (e.g., statins, antiplatelets, hypertension control) is essential.

References

1. Subclavian Steal Syndrome Brian J. Potter, MD, MSc, and Duane S. Pinto, MD, MPH 


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