In an acute myocardial infarction, reciprocal ECG changes often appear as which finding?

• A. ST elevation in I and aVL
• B. ST depression in I and aVL
• C. T-wave inversion in V1 only
• D. ST elevation in aVR only

Answer: (A)

Reciprocal ECG changes come from the heart’s electrical forces pointing toward the injured area, causing the opposite leads to show deviations. In acute myocardial infarction, the leads looking at the area of infarction show ST elevation, while the leads facing the opposite heart wall show ST-segment depression.

For an inferior-wall infarction, the injury current is directed toward the inferior wall, so the inferior leads (the ones that look at the bottom of the heart) show ST elevation. The opposite view—high lateral leads I and aVL—typically exhibit ST-segment depression as the reciprocal change. This pattern helps confirm the infarct and localize it to the inferior wall.

Knowing this, you’d expect reciprocal changes as ST depression in I and aVL when the infarct is inferior. The appearance of ST elevation in I and aVL would not represent reciprocal changes for an inferior infarct; it would suggest involvement of the lateral area itself rather than its opposite wall.

In short, reciprocal changes are ST depression in the leads opposite the infarcted area (e.g., ST depression in I and aVL with an inferior MI).