Elevation in which leads indicates a septal MI?

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

Answer: (C)

Septal infarction affects the interventricular septum, which is best viewed by the anterior chest leads placed at the clock positions V1 and V2. When the septum is injured, the ECG typically shows ST-segment elevation in these leads, reflecting the location supplied by the septal branches of the left anterior descending artery. This distinguishes septal MI from infarctions of other regions: the inferior wall shows elevation in II, III, and aVF; the high lateral wall shows changes in I and aVL; and the anterior/apical regions involve leads like V3-V4. So elevation in V1 and V2 is the telltale sign of a septal MI, with possible extension to V3 if the infarct is larger.