Elevation in which ECG leads indicates an inferior MI involving the right coronary artery?

• A. II, III, aVF
• B. I, aVL
• C. V1-V2
• D. V3-V4

Answer: (A)

Inferior myocardial infarction shows ST-segment elevation in the leads that view the heart from the bottom surface. The limb leads II, III, and aVF are the ones that look at the inferior wall, so when they show ST elevation, it points to injury of the inferior part of the heart. In most people, the right coronary artery supplies this inferior region, so an occlusion there commonly produces this exact pattern.

The other lead groups map to different regions: lateral leads (I and aVL) reflect the lateral wall, while anterior/septal leads (V1-V2 for septal, V3-V4 for anterior) reflect the front of the heart. Their patterns aren’t aligned with an inferior injury, which is why elevations there aren’t the telltale sign of an inferior MI. Reciprocal changes can show up in opposite walls (like ST depression in I or aVL), but the key clue is ST elevation in II, III, and aVF.