Pericarditis, or inflammation of the pericardium, has typical ECG findings. These findings occur in progressive stages, all of which are seen in about 50% of cases of pericarditis.

Stage I (acute phase): Diffuse concave upward ST segment elevation in most leads, PR depression in most leads (may be subtle), and sometimes notching at the end of the QRS complex.

Stage II: ST segment elevation and PR depression have resolved. T waves may be normal or flattened.

Stage III: T waves are inverted and the ECG is otherwise normal.

Stage IV: The T waves return to the upright position thus the ECG is back to normal.

Note: The ECG changes of pericarditis must be distinguished from those of early repolarization. The ST elevation seen in early repolarization is very similar; diffuse and concave upward. However three things may help to distinguish pericarditis from early repolarization:

1) The ratio of the T wave amplitude to the ST elevation should be > 4 if early repolarization is present. In other words, the T wave in early repolarization is usually 4 times the amplitude of the ST elevation. Another way to describe this would be that the ST elevation is less than 25% of the T wave amplitude in early repolarization.

2) The ST elevation in early repolarization resolves when the person exercises.

3) Early repolarization, unlike pericarditis, is a benign ECG finding that should not be associated with any symptoms.