PR depressions on ECG when a patient has pericarditis

Can someone please explain why PR depressions are seen on an ECG when a patient has pericarditis?

That is, from an electrophysiological perspective: what are the exact changes on the cell membrane which cause this specific manifestation/presentation on the ECG?

I’ve asked leading electrophysiologists in my hospital and nobody was able to give me an answer! Thanks