If you can somehow find it, you want a place with graduated independence, although this may be tough in an environment where both cardiac surgeons and cardiac anesthesiologists are so extraordinarily particular about what they like/want/don't want.
Other than that, the 2018 graduate should seek to be facile with 3D and all things echo for structural heart procedures. Everything is going the way of percutaneous/catheter-based intervention (maybe arch vessel dissection and endocarditis surgery will be holdouts?) Would say that "learning echo" and doing complex cases are bare minimum requirements for ACTA programs.