These ECG voltage attenuations are of extracardiac mechanism, and impact the amplitude of QRS complexes, P-waves, and T-waves, occasionally resulting also in shortening of the QRS complex and QT ...

If no P waves can be seen and the QRS complexes are irregularly irregular ... Pericarditis can be distinguished from early repolarization by the ratio of the T wave to the ST elevation.

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 ... ratio of the T wave ...