I'm sure you all know what these are...
Now think about the features with which you've learned to make this diagnosis: the P-R segment changes and the S-T changes. These three ECG's feature another "sign" you can use to make the diagnosis of pericarditis: SPODICK'S SIGN. This is the down sloping of the T-P segment and it may also extend from one QRS to the next. I've underlined this feature below: