What does left dominant coronary circulation mean?

Left Dominant Coronary Circulation: Definition and Clinical Implications

Left dominant coronary circulation means that the posterior descending artery (PDA) and posterolateral artery (PLA) both arise from the left circumflex artery, rather than from the right coronary artery. 1 This anatomical variation affects how blood is supplied to the inferior wall of the left ventricle.

Coronary Dominance Patterns

Coronary dominance is classified into three distinct patterns:

1. Right dominance (most common): The PDA and PLA arise from the right coronary artery
2. Left dominance: The PDA and PLA arise from the left circumflex artery
3. Co-dominance: The right coronary artery supplies the PDA, and the circumflex artery supplies the PLA

The prevalence of these patterns in the general population is approximately:

• Right dominance: 70-80%
• Left dominance: 8-10%
• Co-dominance: 10-12%

Clinical Significance

Left dominant coronary circulation has several important clinical implications:

Mortality Risk

• Left dominance is associated with higher in-hospital mortality following percutaneous coronary intervention (PCI) for acute coronary syndromes compared to right dominance 2
• This increased risk is particularly notable when culprit lesions arise from the left coronary artery

Surgical Considerations

• Patients with left dominance have a higher risk of perioperative myocardial infarction during cardiac surgery 3
• The left main coronary artery tends to be shorter in patients with left dominance (approximately 6.2 mm) compared to those with right dominance (approximately 9.9 mm) 4
• Complete revascularization may be more challenging in left dominant circulation, with a higher inability to revascularize the posterior interventricular artery in left dominant patients 3

Anatomical Considerations

• In left dominant circulation, more than 90% of coronary blood flow enters through the left coronary system
• The entire inferior wall of the left ventricle depends on the left circumflex artery for blood supply
• This creates a situation where a proximal left coronary lesion could potentially compromise a larger territory of myocardium

Diagnostic Identification

Left coronary dominance can be identified through:

1. Coronary angiography: The gold standard for determining coronary dominance
2. Coronary CT angiography: Provides detailed anatomical information about coronary circulation patterns
3. Cardiac MRI: Can help identify coronary dominance patterns in some cases

Clinical Management Implications

When left dominant coronary circulation is identified:

• More aggressive risk factor modification may be warranted
• Earlier intervention might be considered for significant left coronary lesions
• Special attention should be paid to the left circumflex artery during revascularization procedures
• Cardiac surgeons should be informed of this anatomical variation before procedures

Conclusion

Understanding a patient's coronary dominance pattern is important for risk stratification and procedural planning. Left dominant coronary circulation represents an anatomical variant where the left circumflex artery supplies the posterior descending and posterolateral arteries, potentially placing a larger territory of myocardium at risk during coronary events affecting the left coronary system.