ST elevation in leads II, III, aVF indicates?

• A. Inferior STEMI
• B. Anterior STEMI
• C. Lateral STEMI
• D. Posterior STEMI

Answer: (A)

ST elevation in those inferior-facing leads means injury is happening on the bottom wall of the left ventricle. The inferior wall is seen by the heart from the vantage of leads II, III, and aVF, so when these leads show ST elevation, it indicates acute transmural ischemia in that region. In most people, that area is supplied by the right coronary artery, so an occlusion there causes an inferior STEMI (sometimes the left circumflex can be involved in certain coronary anatomies).

You may see reciprocal ST depression in the high lateral leads, such as leads I and aVL, which supports the inferior pattern. This is distinct from other patterns: anterior STEMI would elevate the chest leads over the front wall; lateral STEMI would elevate leads I, aVL, V5, and V6; posterior STEMI often shows ST depression in the anterior leads with a mirror-image pattern in posterior leads (tall R waves in V1–V2) rather than the inferior pattern.