A 35-year-old man presents with sharp chest pain that worsens with deep inspiration and improves when sitting up and leaning forward. ECG shows diffuse ST elevation in leads I, II, III, aVF, and V2 through V6 with PR segment depression in lead aVF. Which finding most strongly supports a diagnosis of acute pericarditis over STEMI?
- A Reciprocal ST depression in aVR
- B ST elevation ratio in lead V6 greater than 25 percent of the T-wave amplitude ✓
- C Notched J point in multiple leads
- D Concurrent first-degree atrioventricular block
Correct answer: B. ST elevation ratio in lead V6 greater than 25 percent of the T-wave amplitude
Explanation
In pericarditis, the ST-to-T wave ratio in V6 exceeding 25 percent strongly favors pericarditis over STEMI. PR segment depression is also characteristic but the ST/T amplitude ratio is the most specific ECG discriminator. Concave ST elevation and diffuse involvement distinguish pericarditis from the territorial elevation of STEMI.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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