Coronary Artery Anatomy: Origins, Course, and Clinical Territories

The coronary arteries supply the myocardium. Anatomic variation is common and clinically crucial for intervention.

Origin and Proximal Course

• Left main coronary artery (LMCA): Arises from left aortic sinus (left coronary cusp); length 1-25 mm (absent in 1% → separate ostia).
• Right coronary artery (RCA): Arises from right aortic sinus (right coronary cusp); courses in right AV groove.

Left Coronary Branches

• LAD (Left Anterior Descending): Anterior interventricular groove → apex. Supplies: anterior septum, anterior LV wall, apex, AV bundle (proximal). Diagonals (D1, D2) → anterolateral LV.
• LCx (Left Circumflex): Left AV groove. Supplies: lateral LV wall, posterior LV (if dominant), SA node (38%), AV node (10%). Obtuse marginals (OM1, OM2) → lateral wall.

Right Coronary Branches

• RCA: Right AV groove → crux. Supplies: RV, inferior LV, posterior septum, SA node (62%), AV node (90%).
• Posterior descending artery (PDA): From RCA (85% right-dominant), LCx (8% left-dominant), both (7% co-dominant). Supplies: posterior 1/3 of septum, inferior wall.
• Posterolateral branches (PLB): Posterolateral LV.

Dominance Patterns

• Right-dominant (85%): RCA → PDA.
• Left-dominant (8%): LCx → PDA.
• Co-dominant (7%): Both supply PDA.

Clinical Correlations

Territory	ECG Changes	Complications
LAD (anterior)	V1-V4 ST↑/↓; new LBBB	LV failure, V-tach, septal rupture, papillary muscle rupture (MR)
LCx (lateral)	I, aVL, V5-V6	LV dysfunction, MR (posteromedial papillary)
RCA (inferior)	II, III, aVF; ST↑ V4R (RV)	AV block (AV node), RV infarct, hypotension (vagal)

Anatomic Variants

• Absent LMCA (separate ostia).
• Ramus intermedius (between LAD/LCx).
• Myocardial bridging (intramuscular LAD segment) — ischemia on exertion.
• Anomalous origin (e.g., LCA from right sinus → sudden death risk if interarterial).

Coronary anatomy guides revascularization strategy (PCI vs. CABG) and predicts ischemic territory.