Dominance is decided by whichever artery gives the posterior descending branch, the right in about 85 per cent
Mnemonic
Dominance is defined by whichever artery gives the posterior descending artery:
- Right dominant - about 85 per cent, the posterior descending arises from the right coronary artery
- Left dominant - about 8 per cent, from the left circumflex
- Co-dominant - the remainder
“The dominant artery supplies the posterior descending, not the most muscle”, which is the usual misconception, since the left coronary supplies far more myocardium in almost everyone.
It matters clinically because in the right dominant majority the right coronary supplies the inferior wall, the sinoatrial node in 60 per cent and the atrioventricular node in 90 per cent, which is why inferior infarction so often causes bradycardia and heart block.
Expansion
- Right dominant - about 85 per cent: the posterior descending artery arises from the right coronary artery
- Left dominant - about 8 per cent: it arises from the circumflex artery
- Co-dominant - the remainder
Nodal supply follows the same pattern:
- Sinoatrial node - right coronary artery in about 60 per cent
- Atrioventricular node - right coronary artery in about 80 to 90 per cent
The clinical consequence is worth holding onto: proximal right coronary occlusion threatens the conducting system as well as the inferior wall.