Patients with acute pericarditis do not always present with the classical findings seen on the previous electrocardiogram. Serial tracings are often needed to differentiate acute pericarditis from other causes of ST segment elevation such as early repolarization and myocardial infarction.

With pericarditis, symmetrical T wave inversion typically develops after the ST segments return to baseline, while in early repolarization the ST segments remain stable.

In acute myocardial infarction, the T wave inversions typically occur prior to resolution of ST segment elevation.

While sinus tachycardia is common, atrial fibrillation may also occur and usually reflects underlying heart disease.