A 58-year-old man with hypertension presents with chest discomfort. His ECG shows ST-segment elevation in leads II, III, and aVF. Which coronary artery is most commonly responsible for inferior wall myocardial infarction?
A. Left circumflex artery
B. Right coronary artery
C. Left main coronary artery
D. Left anterior descending artery
Explanation
Coronary Anatomy and Inferior STEMI
Key Point
The right coronary artery (RCA) is the dominant coronary vessel in approximately 80% of the population and is responsible for the blood supply to the inferior wall of the left ventricle.
Inferior Wall Infarction — ECG Localization
Inferior wall myocardial infarction is identified by ST-segment elevation in the inferior leads: II, III, and aVF. These leads directly face the inferior surface of the left ventricle.
Coronary Artery Distribution
Table
Coronary Artery
Territory Supplied
Infarction Pattern
Right coronary artery (RCA)
Inferior wall, RV (80% of cases)
Inferior STEMI (II, III, aVF)
Left anterior descending (LAD)
Anterior wall, anteroseptal
Anterior STEMI (V1–V4)
Left circumflex (LCx)
Lateral wall, posterolateral
Lateral STEMI (I, aVL, V5–V6)
Left main
Left anterior descending + circumflex territory
Extensive anterior + lateral
High-YieldNEET PG
In dominant RCA systems (80%), the RCA also supplies the AV node and SA node, making inferior STEMI prone to conduction disturbances (heart block, bradycardia).
Clinical Pearl
Right ventricular involvement occurs in 30–50% of inferior STEMIs. Check leads V4R and V5R for RV infarction, which contraindicates nitrates and requires fluid resuscitation.
Why RCA is Most Common
1.
RCA is the dominant coronary in ~80% of individuals (right-dominant system)
2.
RCA directly perfuses the inferior wall and AV nodal artery
3.
Inferior STEMI is the second most common STEMI pattern after anterior (LAD), and nearly all inferior STEMIs are RCA occlusions
Mnemonic
RCA = Right wall = Inferior (RCA supplies the right and inferior territories in a dominant system).
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