Which statement describes the lateral MI ECG features?

• A. ST elevation in I, aVL, V5-V6
• B. ST elevation in II, III, aVF
• C. ST elevation in V1-V3
• D. ST depression in I

Answer: (A)

Lateral myocardial infarction shows injury current most evident in the leads that view the lateral wall of the left ventricle. Leads I and aVL look at the high lateral wall, while V5 and V6 look at the lateral base of the left ventricle. When the left circumflex artery (or a diagonal branch) is occluded, the injured lateral myocardium produces ST elevations in these lateral leads. That pattern—ST elevation in I, aVL, V5, and V6—best matches a lateral MI.

In contrast, ST elevation in II, III, and aVF points to an inferior MI; ST elevation in V1–V3 indicates an anterior/septal MI; and isolated ST depression in lead I would not characterize a lateral MI.