If that many years of schooling seems overwhelming, or you aren’t dead set on cardiology and want some flexibility, consider becoming a Physician Assistant. You would have a minimum of 5 years of education (program begins as a freshman, you’d have three years undergrad and two graduate level if you apply for a 3+2 program). There are some residency programs for specialties, but they aren’t required in most cases. PA’s are free to move from specialty to specialty, so if you decided that pediatric cardiology wasn’t for you after working a year or two, you could move to, say, a pediatric kidney specialist’s office, or even adult orthopedics or family practice, whatever you’d like.