I have a very similar congenital heart defect (tetrology of fallot). I haven't started T yet, but plan to as soon as I get the go-ahead from my cardiologist (fingers crossed). I've been looking for any information I can get, but can't find much information specifically on the risks of testosterone use and CHD's. Generally I think risks of further heart disease become more aligned with cis dudes higher rates. Further, I've read that t increases red blood cell counts making the blood thicker, which I imagine our funky pulmonary valves don't appreciate, but I've also read a prescription for regular blood donations helps with that.
To make matters worse, I'm due for open heart surgery in the next 5-10 years to replace my pulmonary valve and worried about how that might affect top surgery.
Anyway, very curious what your experience has been like since you posted, if you care to share!