Question

An ECG shows ST-segment elevation in leads II, III and aVF in a patient presenting with acute chest pain. Which coronary artery is most likely occluded?

• A. Right coronary artery (RCA)
• B. Left anterior descending artery (LAD)
• C. Left circumflex artery (LCx)
• D. Left main coronary artery

Hint:

Leads II, III, aVF point to the inferior wall - think dominant artery.

Answer 1

The Correct Option is A

Step 1: Localise the infarct from the ECG leads. Leads II, III and aVF are the inferior leads, so ST elevation in these leads indicates an acute inferior wall myocardial infarction.

Step 2: Correlate the inferior wall with its arterial supply. In about 80-90% of people the circulation is right dominant, meaning the posterior descending artery (PDA) arises from the right coronary artery. The RCA therefore supplies the inferior wall of the left ventricle (and usually the SA and AV nodes).

Step 3: Choose the answer. Occlusion of the RCA produces inferior wall MI (II, III, aVF), and may be accompanied by bradyarrhythmias/AV block due to nodal ischaemia and by right ventricular infarction.

Step 4: Why the others are wrong - the LAD supplies the anterior wall and septum (V1-V4 changes); the LCx supplies the lateral wall (I, aVL, V5-V6) and the inferior wall only in left-dominant hearts; left main occlusion causes extensive anterolateral involvement, not isolated inferior changes.

Key fact: Inferior wall MI (II, III, aVF) = RCA occlusion in a right-dominant circulation.