67. What are the four stages of the ECG findings in patient with acute pericarditis?
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.