Coronary arterial dominance
Coronary arterial dominance is defined by the vessel which gives rise to the posterior descending artery (PDA), which supplies the myocardium of the inferior third of the interventricular septum.
Most hearts (80-85%) are right dominant where the PDA is supplied by the right coronary artery (RCA). The remaining 15-20% of hearts are roughly equally divided between left dominant (~10%) and codominant (~20%). The strict definition of codominance can vary depending on which modality one uses to assess the coronary arteries (coronary angiography or CT coronary angiography (CTCA)) but is not overly important. In left dominant hearts the PDA is supplied by the left circumflex artery (LCx) wrapping around the left atrioventricular groove, or less commonly the left anterior descending artery (LAD) coursing around the apex of the heart. In a codominant heart a single or duplicated PDA is supplied by branches of both the RCA and the LAD or LCx.
Although the RCA is the dominant vessel in most hearts, it is important to consider that it is usually the LAD that supplies the majority of the left ventricular myocardium as well as the anterior and mid thirds of the interventricular septum.
Clinical relevance
Dominance has important implications in myocardial ischemia and infarction, imaging of the coronary arteries (CTCA and invasive coronary angiography) and the planning for coronary artery bypass grafting.
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