Coronary Arteries: Anatomy, Dominance, and Clinical Aspects

1. General anatomy

• Coronary arteries arise from the aortic sinuses of Valsalva.
• Right coronary artery (RCA) — from the right sinus.
• Left coronary artery (LCA) — from the left sinus; short main stem (LM, left main) 5–10 mm.
• Non-coronary sinus (posterior) gives off no branches.
• Coronary blood flow in the LV myocardium occurs predominantly in diastole.
• The myocardium extracts 75–80% of O₂ even at rest — increased delivery is only possible via coronary vasodilation.

2. Right coronary artery (RCA)

• Runs in the right AV sulcus.
• Branches:
• — Conus branch (to the pulmonary conus; separate ostium in 50%).
• — Sinus node artery (60%) or from LCx (40%).
• — Acute marginal branch — to the right ventricle.
• — Posterior descending artery (PDA) — in right-dominant circulation.
• — Posterolateral branch to the LV (in right-dominant circulation).
• — AV node artery — in 90% from RCA (via the crux cordis).
• Supplies: right ventricle, right atrium, posterior third of the interventricular septum, sinuatrial (60%) and AV node (90%).

3. Left coronary artery (LCA)

Main stem (LM)

• Short (5–10 mm), from the left sinus to the bifurcation.
• Sometimes trifurcation with an intermediate branch (ramus intermedius).
• Significant LM stenosis > 50% is an indication for CABG (or stenting in special cases).

Left anterior descending artery (LAD)

• In the anterior interventricular sulcus from the LM to the apex (sometimes wraps around it to reach the posterior aspect).
• Branches:
• — Diagonal branches (D1, D2) — anterolateral LV wall.
• — Septal branches (S1 — large) — anterior 2/3 of the interventricular septum + bundle of His and its branches.
• Supplies: anterior LV wall, anterior 2/3 of the septum, apex, partially the lateral LV wall.
• "Artery of sudden death" — proximal occlusion of the LAD before the septal branches.

Circumflex artery (LCx)

• In the left AV sulcus.
• Branches:
• — Obtuse marginal branches (OM1, OM2) — lateral LV wall.
• — Sinus node artery (40%).
• — In left-dominant circulation (7%) — PDA + posterolateral branches.
• Supplies: lateral LV wall, left atrium, in left-dominant circulation — posteroinferior part of the LV.

4. Types of coronary circulation

• Right dominant (85%): PDA and posterolateral branch from the RCA.
• Left dominant (7–8%): PDA from the LCx.
• Codominant (7–8%): PDA from the RCA, posterolateral branch from the LCx.
• Determined by which artery supplies the inferoposterior wall of the LV.

5. Coronary veins

• Great cardiac vein — along the LAD → coronary sinus.
• Middle cardiac vein — in the posterior interventricular sulcus.
• Small cardiac vein — with the RCA.
• Anterior cardiac veins — directly into the right atrium.
• Thebesian veins — directly into the cardiac chambers (physiological shunt).
• The coronary sinus opens into the right atrium (between the IVC and the AV orifice).

6. Blood supply zones — ECG associations

7. Coronary blood flow physiology

• Resting blood flow 250 mL/min (5% of CO).
• In LV myocardium — almost exclusively diastolic (due to high systolic pressure).
• RV myocardium — systolic-diastolic.
• Coronary reserve — ability to increase blood flow by 4–5 times during exertion.
• Metabolic regulation: adenosine (primary), NO, CO₂, H⁺.
• Neurogenic: sympathetic — β₂-vasodilation; parasympathetic — weak.

8. Atherosclerosis and CHD

• Preferred plaque sites — proximal segments: LAD before the first diagonal, LCx before the first OM, proximal RCA.
• Stenosis becomes hemodynamically significant at > 70% (symptomatic angina) and > 50% for LM.
• Fractional flow reserve (FFR) < 0.80 — indication for revascularization.
• iFR (instantaneous wave-free ratio) < 0.89 — adenosine-free alternative to FFR.

9. Coronary artery anomalies

• High take-off, separate ostia of the conus artery.
• Origin from the opposite sinus (LCA from right sinus, RCA from left).
• Interarterial course — LCA between aorta and pulmonary trunk — risk of sudden death in young athletes.
• ALCAPA (origin of LCA from the pulmonary trunk) — severe infantile form.
• Myocardial bridging — tunnel-like course of the artery within the myocardium; often asymptomatic, sometimes ischemia.
• Coronary fistulas — communication with a heart chamber or pulmonary artery.

10. Imaging modalities

• Coronary angiography — invasive gold standard; radial or femoral access.
• CT angiography (CTCA) — non-invasive assessment, high negative predictive value.
• Intravascular ultrasound (IVUS), optical coherence tomography (OCT) — plaque assessment, stent optimization.
• Fractional flow reserve (FFR), iFR — functional stenosis assessment.
• Cardiac MRI with contrast — late gadolinium enhancement (infarct scars), myocardial viability.

11. Revascularization

• PCI (stenting) — most cases of CHD; for LM stenosis, three-vessel disease with low SYNTAX — comparable to CABG.
• CABG (coronary artery bypass grafting) — three-vessel disease, LM, patients with DM + multivessel disease, low EF.
• Grafts: left internal thoracic artery (LIMA) to LAD — best long-term outcome; right internal thoracic, radial artery, great saphenous vein.

12. FAQ

Why is the LAD called the "widow maker"?
Proximal LAD occlusion leads to extensive anterior and septal wall infarction, often with cardiogenic shock and high mortality.

How to determine dominance type on coronary angiography?
By the origin of the PDA: if from RCA — right-dominant, from LCx — left-dominant, if both contribute — codominant.

What is the SYNTAX score?
An assessment of coronary lesion complexity. < 22 — PCI preferred; 23–32 — individual choice; > 32 — CABG preferred.

Why is the right ventricle less commonly affected by infarction?
Smaller muscle mass, systolic-diastolic blood flow, more collaterals. RV infarction is more common with proximal RCA occlusion.

What is the "slow-flow/no-reflow" phenomenon?
Microcirculatory dysfunction following successful arterial opening (stenting): despite patency of the main vessel, contrast flow is delayed. Causes: distal embolization, edema, microthrombosis. Treatment — intracoronary nitroprusside, epinephrine, verapamil.

See also: Myocardial infarction · Angina pectoris · ECG · Aorta · Anatomy catalog