Often, the P wave is inverted in lead II, if it can be seen at all. A pacemaker may be needed to relieve symptoms when no reversible cause — i.e. AV blocking medications or electrolyte ...

If no P waves can be seen and the QRS complexes ... can be from acute pericarditis or an atrial infarction. Diffuse T wave inversion is stage III of the ECG changes in pericarditis.