I wouldn't invest too much thought into what specialty you want to go into because you haven't started medical school yet and thus have little experience or background upon which to make a decision. Most med students change their minds a dozen times before they graduate.
In terms of internships, what do you expect out of one? They can be highly variable. I got an offer to direct a sustainability project at a nursing home. I didn't expect much clinical or medical exposure from that. See what your school has to offer in terms of partnerships with hospitals or other firms.
Any accredited medical school, MD and DO will prepare you to apply and get into a surgical residency. After that, you could do a cardiothoracic fellowship. There may be some cardiothoracic residencies but I'm not sure.
