This post from Dr. Smith's ECG blog discusses some quantitative aspects of the electrocardiographic evaluation of possible pericarditis including the ST/T ratio and the magnitude of PR segment depression (not all PR depression is due to pericarditis!).
A case presentation of a patient repeatedly misdiagnosed as having pericarditis discusses some cognitive traps along the way. One that I was intuitively aware of but had never seen mentioned in print before was referred to by the presenter as overconfidence inspired by scientific intrigue. You could also call it the “hey, I just made a really cool diagnosis” heuristic. If you think you've just made a cool diagnosis, watch out. It's emotionally intoxicating and further thinking tends to stop.