What distinguishes STEMI from NSTEMI?

What distinguishes STEMI from NSTEMI?

• A. ST-segment elevation on ECG is required to diagnose STEMI.
• B. ST-segment depression in two contiguous leads defines STEMI.
• C. T wave inversion defines STEMI.
• D. ST-segment elevation ≥1 mm in two contiguous leads or new left bundle branch block.

Answer: (D)

The main idea here is that STEMI and NSTEMI are distinguished by the ECG pattern of a heart attack. STEMI reflects a full-thickness (transmural) injury from an acute occlusion and is defined by ST-segment elevation in two contiguous leads, or a new left bundle branch block. That’s why the correct statement emphasizes ST-segment elevation with a specific qualifier: ST-segment elevation ≥1 mm in two contiguous leads or a new LBBB. This captures the key signal that an artery is abruptly blocked and the entire thickness of the heart wall is at risk, demanding urgent reperfusion. Why the other ideas don’t fit: ST-segment depression in two adjacent leads isn’t diagnostic of STEMI—it’s more typical of subendocardial ischemia and NSTEMI. T wave inversion alone isn’t specific for STEMI either; it can appear with ischemia or during recovery and doesn’t indicate a full-thickness infarction. Also, saying ST-segment elevation is required to diagnose STEMI is incomplete because a new left bundle branch block can serve as a STEMI equivalent even without obvious ST elevations, so the best criterion explicitly includes that possibility.

The main idea here is that STEMI and NSTEMI are distinguished by the ECG pattern of a heart attack. STEMI reflects a full-thickness (transmural) injury from an acute occlusion and is defined by ST-segment elevation in two contiguous leads, or a new left bundle branch block. That’s why the correct statement emphasizes ST-segment elevation with a specific qualifier: ST-segment elevation ≥1 mm in two contiguous leads or a new LBBB. This captures the key signal that an artery is abruptly blocked and the entire thickness of the heart wall is at risk, demanding urgent reperfusion.

Why the other ideas don’t fit: ST-segment depression in two adjacent leads isn’t diagnostic of STEMI—it’s more typical of subendocardial ischemia and NSTEMI. T wave inversion alone isn’t specific for STEMI either; it can appear with ischemia or during recovery and doesn’t indicate a full-thickness infarction. Also, saying ST-segment elevation is required to diagnose STEMI is incomplete because a new left bundle branch block can serve as a STEMI equivalent even without obvious ST elevations, so the best criterion explicitly includes that possibility.