Which assessment finding on an ECG is characteristic of a myocardial infarction?

The characteristic finding of a myocardial infarction (MI) on an electrocardiogram (ECG) is ST elevation. During an MI, particularly in cases of ST-Elevation Myocardial Infarction (STEMI), there is a significant disruption in the heart's blood supply, causing injury to the heart tissue. This injury affects the electrical activity of the heart, which is reflected in the ECG.

When myocardial tissue becomes ischemic (lacking adequate blood supply), the ST segment of the ECG tracing may become elevated. This elevation occurs because the injured cardiac muscle cells have altered ionic balances, leading to changes in the depolarization and repolarization processes that are detected as changes to the ST segment.

Recognizing ST elevation is critical as it indicates that there is an active and ongoing myocardial injury, which often requires immediate medical intervention for the best chance of preserving heart tissue and function.