A 52-year-old Indian man with diabetes and hyperlipidemia develops acute chest pain with ST elevation in leads II, III, and aVF. Which is the most common site of coronary artery occlusion in inferior wall STEMI?

Question

Accepted Answer

A. Proximal right coronary artery. ## Inferior Wall STEMI: Culprit Vessel and Site

**Key Point:** The right coronary artery (RCA) is responsible for approximately 80% of inferior wall STEMIs, with the proximal RCA being the most common occlusion site.

### Anatomical Basis of Inferior STEMI

Inferior wall STEMI (ST elevation in II, III, aVF) indicates occlusion of a vessel supplying the inferior wall of the left ventricle:

| Vessel | Blood Supply | Frequency in Inferior STEMI |
|---|---|---|
| **Right coronary artery (RCA)** | **Inferior LV, RV, AV nodal artery, SA nodal artery** | **~80%** |
| Left circumflex artery (LCx) | Inferior LV (in left-dominant systems) | ~15–20% |
| Left anterior descending (LAD) | Rarely causes isolated inferior STEMI | <5% |

**High-Yield:** RCA dominance (present in ~70% of the population) makes RCA occlusion the most common cause of inferior STEMI. In right-dominant systems, the RCA supplies the inferior wall, posterior descending artery (PDA), and posterolateral branches.

### Proximal vs. Distal RCA Occlusion

| RCA Occlusion Site | Clinical Features | Complications |
|---|---|---|
| **Proximal RCA** | ST elevation II, III, aVF + RV involvement | **Bradycardia, AV block, cardiogenic shock** |
| Distal RCA (after RV branches) | ST elevation II, III, aVF only | Minimal RV involvement |

**Clinical Pearl:** Proximal RCA occlusion is the most common site because:
1. Atherosclerosis burden is highest in proximal segments
2. Plaque rupture occurs more frequently at branch points
3. Proximal occlusion causes the largest infarct territory

**Mnemonic:** **RCA = Right Coronary Artery = Responsible for 80% of inferior STEMI** — In a right-dominant system (70% of people), RCA supplies the inferior wall.

### Diagnostic Clue
ST elevation in leads II, III, aVF with reciprocal ST depression in I and aVL = **RCA occlusion** (inferior STEMI). If RV involvement is present (ST elevation in V4R), this confirms proximal RCA occlusion.

Answer

B. Distal left anterior descending artery

Answer

C. Left main coronary artery

Answer

D. Left circumflex artery at the obtuse marginal branch

A 52-year-old Indian man with diabetes and hyperlipidemia develops acute chest pain with ST elevation in leads II, III, and aVF. Which is the most common site of coronary artery occlusion in inferior wall STEMI?

Explanation

Inferior Wall STEMI: Culprit Vessel and Site

Anatomical Basis of Inferior STEMI

Proximal vs. Distal RCA Occlusion

Diagnostic Clue

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Vessel	Blood Supply	Frequency in Inferior STEMI
Right coronary artery (RCA)	Inferior LV, RV, AV nodal artery, SA nodal artery	~80%
Left circumflex artery (LCx)	Inferior LV (in left-dominant systems)	~15–20%
Left anterior descending (LAD)	Rarely causes isolated inferior STEMI	<5%

RCA Occlusion Site	Clinical Features	Complications
Proximal RCA	ST elevation II, III, aVF + RV involvement	Bradycardia, AV block, cardiogenic shock
Distal RCA (after RV branches)	ST elevation II, III, aVF only	Minimal RV involvement