fontan procedure and weight lifting

hello,
i am 24 yrs old and had the fontan procedure done when i was ten years old. i was born with alot of heart problems. i weight about 120 lbs and have started lifting weights. i had read that it may not be advised due to the fontan procedure. i would realy like to continue to lift weights even if i could just use 10 lbs weights and lift them alot. i would like to know if this is discouraged due to the fontan procedure. i assumed exercise would be good, but i've read that only low intensity should be done.

thankyou very much.