What is the biggest difference between STEMI and NSTEMI?

• A. The blood flow to the heart is completely blocked.
• B. ST elevation is always present on the ECG for NSTEMI.
• C. Troponin is never elevated in STEMI.
• D. NSTEMI has a larger area of tissue damage than STEMI.

Answer: (C)

STEMI and NSTEMI differ mainly in the ECG and the extent of artery blockage. In a STEMI, the ECG shows ST-segment elevation, which reflects a full-thickness (transmural) infarction from typically a complete occlusion of a coronary artery. NSTEMI, on the other hand, does not show ST-segment elevation; instead there may be ST depression or T-wave changes, indicating subendocardial ischemia from a partial or non-occlusive blockage.

Troponin rises in both conditions because both involve injury to heart muscle, so the notion that troponin is never elevated in STEMI isn’t correct. The amount of tissue damage tends to be larger with STEMI due to the full-thickness infarction, though the exact size can vary.

So the key difference is the presence of ST-segment elevation on the ECG for STEMI, with NSTEMI lacking that elevation.