Coronary Artery Anatomy: Arteries, Branches & Dominance
The coronary arteries feed the heart itself — and knowing which vessel supplies which wall is the backbone of reading an ECG and understanding a heart attack.
The coronary arteries at a glance
Two main coronary arteries arise from the aorta just above the aortic valve: the left main and the right coronary artery. The left main quickly divides into the left anterior descending and the circumflex, so clinicians speak of three major vessels — the LAD, the circumflex, and the RCA — each supplying a defined territory of heart muscle.
Where the coronaries begin
The coronaries originate from the aortic sinuses (sinuses of Valsalva) — small pouches behind the cusps of the aortic valve. The left main comes from the left sinus, the RCA from the right sinus. They fill mainly during diastole, when the aortic valve is closed and the muscle is relaxed.
The left coronary system: LAD and circumflex
The left main coronary artery is short and splits into two:
- Left anterior descending (LAD) — runs down the front of the heart in the anterior interventricular groove, giving off septal and diagonal branches. It supplies the anterior wall, the interventricular septum, and the apex.
- Left circumflex (LCx) — curves around the left side in the atrioventricular groove, giving obtuse marginal branches. It supplies the lateral wall.
The right coronary artery (RCA)
The right coronary artery runs in the right atrioventricular groove and supplies the right ventricle, the inferior wall, and — in most people — the SA and AV nodes. This is why an inferior heart attack (an RCA occlusion) so often brings bradycardia and heart block.
Which artery supplies which wall
| Artery | Wall supplied | ECG leads |
|---|---|---|
| LAD | Anterior wall, septum, apex | V1–V4 |
| Circumflex | Lateral wall | I, aVL, V5–V6 |
| RCA | Inferior wall, RV, SA/AV nodes | II, III, aVF |
This map is exactly how a STEMI is localised on the ECG.
Coronary dominance
Dominance is defined by which artery gives rise to the posterior descending artery (PDA):
- Right dominant (~85%) — the PDA comes from the RCA.
- Left dominant (~8%) — the PDA comes from the circumflex.
- Co-dominant (~7%) — both contribute.
Key takeaways
- Three major vessels: LAD, circumflex (from the left main), and RCA.
- They arise from the aortic sinuses and fill in diastole.
- LAD → anterior/septum; circumflex → lateral; RCA → inferior + nodes.
- Artery, wall, and ECG leads are one linked concept.
- Dominance is defined by the origin of the PDA (RCA in ~85%).
Practise cardiac anatomy
Test coronary arteries, dominance, and conduction questions.
Practise Anatomy →Frequently asked questions
What are the main coronary arteries?
The left main (which divides into the left anterior descending and circumflex) and the right coronary artery — giving three major vessels: LAD, circumflex, and RCA.
Where do the coronary arteries originate?
From the aortic sinuses (sinuses of Valsalva), just above the cusps of the aortic valve.
Which coronary artery supplies the inferior wall?
The right coronary artery in most people, which is why an inferior MI shows in leads II, III, and aVF.
What does the LAD supply?
The anterior wall of the left ventricle, the interventricular septum, and the apex.
What is coronary dominance?
It is defined by which artery gives rise to the posterior descending artery — the RCA in right dominance (about 85%) and the circumflex in left dominance.
When do the coronary arteries fill with blood?
Mainly during diastole, when the heart muscle is relaxed and the aortic valve is closed.
Sources & further reading
- Cardiovascular Credentialing International (CCI)
- American College of Cardiology
- American Heart Association
- MedlinePlus (U.S. National Library of Medicine)
External links are provided for reference; always confirm current details with the official source.