To do true Peds CT as a full-time gig, you are looking at 7+years residency. The guy I know did 5 years GS, 2 years CT and 2 peds CT years, but that was 15 years ago. If you have read "Walk on Water", you know that some of those guys are entering year 12 of residency.
One of my professors at Sick Kids in Toronto did, if I can remember correctly, 5 yrs. general surgery, 3 yrs cardiac and 1 yr pediatric cardiac. I asked him if that's the norm and he said, "Well, you may be able to shorten it a bit, but you probably wouldn't get a very good job."
I know at Toronto, virtually every surgical resident is "strongly encouraged" to pursue a graduate degree as part of their training as the school's goal is to produce academic surgeons, so this can add to the time. But I don't know if this applies in the States as most if not all major centres here that do these types of procedures are attached to universities.