What is the coronary steal phenomenon?

Coronary Steal Phenomenon

The coronary steal phenomenon occurs when vasodilators cause maximal coronary arteriolar vasodilation, resulting in increased blood flow to territories supplied by normal coronary arteries while diverting blood away from areas supplied by stenotic vessels, potentially causing myocardial ischemia. 1

Pathophysiology

• Coronary steal occurs when vasodilating agents (like dipyridamole or adenosine) cause maximal coronary arteriolar vasodilation in territories supplied by normal coronary arteries 1
• This increased flow in normal vessels can divert blood away from territories supplied by stenotic arteries, as the obstructed vessels cannot increase flow to match the vasodilation 1
• The phenomenon is characterized by a redistribution of coronary blood flow that paradoxically reduces perfusion to already compromised myocardial regions 1

Clinical Manifestations

• During pharmacological stress testing, coronary steal may manifest as new or worsening wall-motion abnormalities on echocardiography, indicating ischemia 1
• Symptoms may include chest pain, dyspnea, and ECG changes consistent with myocardial ischemia 1
• The severity of symptoms correlates with the degree of coronary stenosis and the extent of collateral circulation 2

Types of Coronary Steal Syndromes

1. Pharmacologically-Induced Coronary Steal

• Occurs during stress testing with vasodilators like dipyridamole and adenosine 1
• Used diagnostically to detect coronary artery disease during stress echocardiography or nuclear perfusion imaging 1
• Side effects include flushing, chest pain, headache, dyspnea, and can be reversed with aminophylline 1

2. Coronary-Subclavian Steal Syndrome (CSSS)

• Occurs in patients with coronary artery bypass grafting (CABG) using the internal mammary artery 3
• Results from stenosis or occlusion of the subclavian artery proximal to the internal mammary artery origin 3
• Causes retrograde blood flow from the internal mammary artery graft into the subclavian artery 4
• Can lead to myocardial ischemia, unstable angina, and even myocardial infarction 3, 4
• Occurs in approximately 2.5-4.5% of patients referred for CABG 4

3. Coronary Artery Fistula-Related Steal

• Abnormal connections between coronary arteries and cardiac chambers or great vessels can divert blood flow 5
• Can cause significant myocardial ischemia through the steal mechanism even in the absence of coronary artery disease 5
• May present with acute coronary syndrome or even sudden cardiac arrest in severe cases 5

Diagnostic Approaches

• Stress echocardiography with vasodilators can demonstrate the steal phenomenon through new or worsening wall-motion abnormalities 1
• For subclavian steal, bilateral arm blood pressure measurements showing a difference >15-20 mmHg suggests subclavian artery stenosis 2, 6
• Duplex ultrasonography can identify reversal of flow in the vertebral artery in subclavian steal syndrome 2
• CT angiography or MR angiography can definitively identify stenosis of the subclavian artery 2, 6
• Coronary angiography may be needed to identify coronary fistulas or assess the severity of coronary disease 5

Management

For Pharmacologically-Induced Steal (During Testing)

• Aminophylline can reverse the effects of dipyridamole or adenosine 1
• Monitor for prolonged ischemic responses and treat with intravenous β-adrenergic blockers if needed 1

For Coronary-Subclavian Steal Syndrome

• Revascularization is recommended for symptomatic patients 6
• Endovascular options (angioplasty and stenting) have high initial success rates (93-98%) 6
• Surgical options like carotid-subclavian bypass have excellent long-term patency (96-100% at 5 years) 6, 3
• Percutaneous revascularization is generally considered first-line therapy 4
• Screening with bilateral blood pressure measurements before CABG can help prevent CSSS 4

For Coronary Artery Fistulas

• Surgical or percutaneous closure of significant fistulas may be necessary to prevent coronary steal 5

Clinical Pearls and Pitfalls

• The coronary steal phenomenon can occur in patients with no obstructive coronary disease if there are anomalous vascular connections 5
• Not all patients with flow reversal in vessels will be symptomatic - clinical correlation is essential 6
• Coronary steal should be suspected in patients presenting with angina after CABG, particularly with arm exercise 4
• The term "steal" has expanded beyond explicit flow reversal to include various mechanisms that decrease stress flow 7
• Screening for subclavian stenosis with bilateral arm blood pressure measurements is recommended before using the internal mammary artery for CABG 4