Acute pericarditis is a common disease in patients experiencing chest pain, accounting for approximately 5% of emergency department presentations with chest pain.3 The condition may develop into cardiac tamponade, with which the in-hospital mortality rate was 1.1%.3 Therefore, the identification of AP is crucial in medical practice. The ECG is useful in the diagnosis of AP, with changes occurring in about 90% of patients.4 Changes on ECG are classically divided into 4 stages.4 Stage I typically occurs during chest pain and is mainly characterized by multilead ST elevations and PR depression. The PR segment represents the atrial repolarization. The depression of the PR segment, which is very specific to AP and denotes subepicardial atrial injury, occurs in all leads except aVR and usually V1, in which PR elevation is the usual finding.4 This stage may last up to 2 weeks after initial symptoms. However, this stage lasted less than 1 week in the present case, which might have been because of aggressive anti-inflammatory treatment. Stage II is represented by the fall of the ST segment to baseline and flattening of T waves. Stage III is characterized by the inversion of T waves in almost all leads (opposite to the original direction of the ST segment). Gradual resolution of T-wave inversion occurs in stage IV. Although AP exhibits characteristic changes in stage I on ECG, 2 conditions that are commonly confused with AP include STEMI and early repolarization.