ST elevations in V1–V4 with reciprocal ST depression in II, III, and aVF indicate infarction of which wall?

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ST elevations in V1–V4 point to injury of the anterior wall of the left ventricle, which is supplied mainly by the left anterior descending artery. The presence of reciprocal ST depression in the inferior leads (II, III, aVF) supports this, because the electrical vector from an anterior-wall infarct tends to move away from the inferior leads, producing depressions there while elevating the anterior leads.

If the infarct were posterior, you’d expect changes opposite to the front: either ST depression in the anterior leads or the appearance of posterior changes on dedicated posterior leads (or a tall R wave in V1 rather than sustained ST elevation). A lateral-wall infarct would involve the lateral leads (I, aVL, V5–V6) rather than primarily V1–V4. An inferior-wall infarct would show ST elevations in II, III, and aVF with reciprocal depression in I and aVL, not the pattern described.