I wouldn't take that workload if you want to provide appropriate and safe patient care. I work on a cardiac step-down unit right now that staffs 1:4 most of the time and that is a bit much the majority of the time. A good nurse to patient ratio would be 1:3, in my opinion.
Our unit takes patients with drips and also pre and post-op CABG. Post cath pts. can vagal and go down hill very quickly without warning then your ACLS kicks in. That is way too much when you have other pts. in the same kind of status as that one or worse. Post-op CABG pts. are a tremendous responsibilty and things could go wrong within seconds.
Don't risk your license or your health by taking on too big of a responsibility. Good luck with your decision!!