Yes, I have had choriamnionitis in April 2010. I got it after prolonged premature rupture of membranes. My membranes around 'twin 1', Megan, went at 14+5 and at 23+5 (I was in hospital at that time awaiting a decision on treatment for blood clots in my lungs) I woke up with symptoms of infection, which rapidly got worse. By 2pm, Megan had been born and it was obvious (because of the amount of puss) that I had had an infection for weeks, but had had no symptoms of it and although I was being regularly and properly monitored it hadn't shown up at all. Sadly, because my waters had gone so early, which meant there was little chance for lung development to happen, because she was so premature and because of the infection, we lost Megan when she was 15 minutes old. Her sister, Imogen was born at 2.11pm and she lived in NICU for 9 days. She was just too premature to survive, although she was a fighter, they both were!
I had been aware of the risk of infection from the time my waters had gone and had a lot of time to research, so I knew about choriamnionitis before I had it. I have since been pregnant again and although I have had several early miscarriages, these are due to a blood disorder, not the choriamnionitis. I do now have a baby girl, who I had since the infection and everything was fine in my pregnancy with her, although they did query 'foul smelling' amniotic fluid at her birth, but no infection showed and she was fine.
I am not sure if this helps. Good luck with your son's heart scan.