my fellow pedi peeps who've replied have it right. Noone wants you doing pedi hearts just cause you did a bunch during residency. Peds fellowship gives you much more experience with them, but in order to be a pediatric cardiac anesthesiologist comfortable doing any pedi heart case, you MUST do some advanced training-- there are debates as to how much, how long-- at our institution we are doing 6 months minimum of mentored training with an experienced pedi cardiac anesthesiologist. Helpful to do fellowship wherever you think you're going to end up working so that you learn the ways and whims of the pedi cardiac surgeon(s) in a mentored environment before you're on your own. If you're not staying on as an attending at that hospital, you'll most likely have another "mentored" phase (a week-month) before you're sent off on your own. As of now, our pedi cardiac "fellows" are paid as attendings because they still work in the general peds OR and take peds OR call. So it's a pretty good gig.