What is the significance of ST-segment elevation on an ECG?

• A. Indicates marginally reduced blood flow without infarct
• B. Indicates ventricular arrhythmia
• C. Indicates acute ST-elevation myocardial infarction (MI)
• D. Indicates pericarditis only

Answer: (C)

ST-segment elevation on an ECG signals acute transmural myocardial injury from a sudden coronary occlusion, i.e., an acute ST-elevation MI. The injury current from full-thickness myocardium in jeopardy shifts the ST segment upward in the leads that face the affected area. This finding is a medical emergency and calls for rapid reperfusion—urgent PCI if available within about 90 minutes, or thrombolysis if PCI isn’t accessible within the recommended window. It’s distinct from NSTEMI, where ST segments aren’t elevated but troponin is elevated and ischemia is present; it’s also not typical of pericarditis, which produces more diffuse ST elevation often with PR depression.