Which statement best describes ST elevations in myocardial infarction?

• A. ST elevations occur only in STEMI.
• B. ST elevations occur in NSTEMI.
• C. ST elevations occur in both NSTEMI and STEMI.
• D. ST elevations are not used to differentiate MI.

Answer: (A)

ST-segment elevation on the ECG signals a full-thickness (transmural) myocardial injury due to a complete blockage of a coronary artery, which defines an ST-elevation MI. In contrast, NSTEMI typically involves subendocardial ischemia from partial or temporarily resolved occlusion and usually shows ST depression or T-wave inversions rather than true ST elevations. Because ST elevations point to a transmural infarct requiring urgent reperfusion, they are not characteristic of NSTEMI. Thus, the statement that ST elevations occur only in STEMI aligns with how the ECG is used to distinguish STEMI from NSTEMI in practice. There are rare exceptions in ECG presentations, but for standard clinical differentiation, this pattern is the most accurate.