Which ECG finding is most indicative of acute pericarditis in the early phase?

• A. Normal sinus rhythm
• B. Sinus tachycardia
• C. T wave inversions
• D. Diffuse ST segment elevations

Answer: (D)

Acute pericarditis inflames the pericardial lining and creates a global injury current, so the ECG shows widespread changes across many leads. In the early phase this manifests as diffuse ST segment elevations, often with a concave shape, and may be accompanied by PR-segment depression. This pattern is far more characteristic of pericarditis than a single-territory ST elevation seen in myocardial infarction, which helps distinguish it from other causes. While normal rhythm or sinus tachycardia can occur, they are nonspecific, and T wave inversions tend to appear later as the process evolves. So the diffuse, widespread ST elevations best indicate early acute pericarditis.