Coronary predominance
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Here is a comprehensive explanation of coronary predominance (dominance):
Coronary Predominance (Dominance)
Definition
Coronary dominance is defined by which coronary artery gives rise to the posterior descending artery (PDA) - also called the posterior interventricular artery - which runs in the inferior interventricular groove and supplies:
- The posterior third of the interventricular septum
- The inferior/posterior wall of the left ventricle
The artery that supplies the PDA is called the dominant artery. This definition is purely anatomical and has nothing to do with size or the number of branches.
- Fuster and Hurst's The Heart, 15th Ed.: "The artery that supplies the major posterior descending artery is commonly referred to as the dominant artery."
- Harrison's Principles of Internal Medicine 22E: "When the right coronary artery is the origin of the atrioventricular nodal branch, the posterior descending artery, and the posterior lateral vessels, the circulation is defined as right dominant."
Types
| Type | PDA Origin | Frequency |
|---|---|---|
| Right dominant | Right coronary artery (RCA) | ~80-90% |
| Left dominant | Left circumflex artery (LCx) | ~10-15% |
| Codominant | Both RCA and LCx contribute | ~5-10% |
- Robbins & Kumar Basic Pathology: "The posterior descending artery can arise from either the RCA (in 90% of individuals) or the LCX."
- Miller's Anesthesia, 10e: "In 85% of the population, the RCA gives rise to the posterior descending artery supplying the posterior inferior aspect of the left ventricle ('right-dominant' system). In 15% of patients, the LCx gives rise to the posterior descending artery ('left-dominant' system)."
Visual - Left Dominant Circulation (CT Angiography)
The image below shows a left dominant coronary system. Note the circumflex (Cx) giving rise to the posterior descending artery (PD), and the short RCA leaving the right atrioventricular groove (RAVG) nearly empty - a normal finding in left dominance, not to be confused with RCA occlusion.
Grainger & Allison's Diagnostic Radiology - Fig. 12.11 Coronary Dominance
Clinical Significance
1. AV node blood supply
The AV nodal artery arises from the dominant artery. This means:
- In right dominance: AV node is supplied by RCA - RCA occlusion can cause heart block
- In left dominance: AV node is supplied by LCx
2. Patterns of myocardial infarction
- Robbins & Kumar: "In a right dominant heart, occlusion of the RCA leads to posterior septal and posterior wall ischemic injury. In a left dominant heart, where the posterior descending artery arises from the circumflex artery, occlusion of the LCX generally affects the left lateral wall as well as the posterior third of the septum, and the inferior and posterior wall of the left ventricle."
3. Prognosis in acute coronary syndromes
Left dominance is associated with worse outcomes in ACS, since LCx occlusion in a left dominant system results in a much larger territory of myocardial ischemia.
4. CABG and PCI planning
Knowing dominance is critical for revascularization planning - the dominant artery supplies more myocardium and its occlusion has greater hemodynamic consequences.
5. Congenital heart disease association
Left coronary dominance is up to 3 times more common in truncus arteriosus than in the general population. (Fuster and Hurst's The Heart, 15th Ed.)
Summary
| Feature | Right Dominant | Left Dominant |
|---|---|---|
| PDA origin | RCA | LCx |
| AV node supply | RCA | LCx |
| Frequency | ~85-90% | ~10-15% |
| RCA occlusion consequence | Larger (inferior LV + septum + AV node) | Smaller (RV branches only) |
| LCx occlusion consequence | Smaller (lateral LV only) | Larger (lateral + inferior LV + AV node) |
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