now these are the fields that actually provide very rare service:

cardio: any imaging or procedures that they do is offlimits to anybody else. you feel dizzy, u have a murmur, even a nurse can send u to a cardiologist. need a pacemaker, who else is going to do it? aortic valve replacement=about 100cardiologists in usa do it, nobody else.

any surgical subspecialty: it's obvious ophtho or ortho or ent is offlimits to anybody else. people will pay cash for a hip replacement if they have to.

derm: again even a nurse can tell u u got a wart, but only a derm will freeze it(and it will take him 1minute instead of doing a "history&physical".

but all those specialties are offlimits to me:( I think about radio because it's the closest to something like cardio. but I wouldn't go through 3yrs of IM residency just to start a cardio fellowship. that's too much trouble.

(http://www.autoadmit.com/thread.php?thread_id=2501381&forum_id=2#25068487)