Origin: Arises from the left aortic sinus of the ascending aorta.
Branches:
- 🌟 Left Anterior Descending (LAD) – “widowmaker” when proximally occluded; gives off septal and diagonal branches.
- ↪️ Left Circumflex (LCx) – gives obtuse marginal branches.
Supplied Areas:
- LAD: Anterior LV wall, anterior 2/3 septum, apex.
- LCx: Lateral LV wall, ± posterior wall (especially in left dominance).

💙 Right Coronary Artery (RCA)

Origin: Arises from the right aortic sinus of the ascending aorta.
Branches:
- Posterior Descending Artery (PDA): Arises from RCA in ~85% (right-dominant).
- Right Marginal Artery: Supplies RV free wall.
Supplied Areas:
- RCA: Right atrium, RV, SA node (60%), AV node (80%).
- PDA: Inferior wall LV, posterior 1/3 of septum.

🫀 Coronary Anatomy

Coronary Artery	Origin	Branches	Supplied Areas
LCA	Left aortic sinus	LAD (septal + diagonal), LCx (obtuse marginals)	LAD → anterior LV, septum, apex LCx → lateral LV, posterior wall (in left dominance)
RCA	Right aortic sinus	PDA (in 85%), Right marginal	RA, RV, SA node, AV node; PDA → inferior LV, posterior septum
PDA	RCA (85%) or LCx (8–10%)	N/A	Posterior LV wall + septum
LMCA	Left aortic sinus	Divides into LAD + LCx	Supplies most of LV

📉 Coronary Arteries & ECG Changes

Artery	Leads Affected	ECG Changes	Area Supplied
LAD	V1–V4	ST ↑, Q waves, T inversion	Anterior LV, septum
LCx	I, aVL, V5–V6	ST ↑ lateral leads	Lateral LV
RCA	II, III, aVF	ST ↑ inferior leads	Inferior LV, RV
PDA	V7–V9 (posterior leads)	ST ↑ posterior; ST ↓ V1–V3 (reciprocal)	Posterior LV
LMCA	V1–V6, I, aVL	Widespread ST changes	Large LV territory

💡 Coronary Blood Flow

Coronary perfusion is unique: maximal in diastole (when myocardium relaxes). Perfusion depends on myocardial oxygen demand, autoregulation, and vessel calibre.

⚙️ Blood Flow Dynamics

⏱️ Diastolic Dominance: Flow reduced in systole due to compression.
🔄 Autoregulation: Maintains steady flow despite BP changes.
💪 Demand-driven: Increases with exertion, stress, tachycardia.

🧬 Factors Influencing Coronary Flow

Resistance (diameter, viscosity, cardiac cycle).
Metabolic vasodilators: Adenosine, K⁺, CO₂.
Neural/hormonal control: Sympathetic ↑ constriction; Parasympathetic → dilation.
Atherosclerosis → narrowed lumen, ischaemia, angina, MI. ⚠️

🚫 Constrictors

Norepinephrine/Epinephrine (α-effect), Endothelin-1, Angiotensin II, Thromboxane A2, Serotonin (5-HT).

✅ Dilators

Nitric Oxide (NO), Prostacyclin (PGI₂), Adenosine, Bradykinin, β-agonists (e.g. Isoproterenol), Calcium channel blockers.

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Coronary Artery Anatomy

❤️ Left Coronary Artery (LCA)