I had pericarditis once. Put me in the hospital for a week. It made my heart go out of rhythm for a while. It would hurt my chest, I'd get really dizzy, pretty weak. I had to take blood thinners for a while, some other medicine for a while. I needed to wear a heart monitor for a week after I got out of the hospital too. Kinda scary at times. I felt like I was having a heart attack all the time. I came close to needing to be defibrillator blasted to bring me back into rhythm, but luckily I didn't need it. I had to take it kind of easy for a while. According to what I read, DD's is not quite as severe as mine was, although it's still scary to go through it. He should be fine, just needs to take it easy for a bit.