Which lead set best identifies a lateral wall MI?

• A. II, III, aVF
• B. V1-V2
• C. I, aVL, V5, V6
• D. V3-V4

Answer: (C)

Identifying a myocardial infarction location on ECG comes down to which leads show ST-segment elevation and what region those leads view. A lateral wall MI involves the outer left side of the heart, primarily supplied by the left circumflex artery. The leads that visualize this area are the high lateral limb leads I and aVL, along with the left lateral chest leads V5 and V6. When a lateral wall infarct occurs, ST elevation tends to appear in these specific leads, reflecting the affected territory across both the limb and chest views.

This pattern is why the combination of leads I, aVL, V5, and V6 is the best indicator of a lateral wall MI. In contrast, ST elevations in II, III, aVF point to the inferior wall, V1-V2 point to the septum, and V3-V4 point to the anterior wall, which do not correspond to the lateral region.