This is probably because of a shortage of highly competent medical personnel, especially in rural areas where no top medical school graduate in her right mind would want to work, just like they probably wouldn't want to live and work in someplace like Iran.
I don't really see any way to fix this. Getting excellent medical care means having excellent medical professionals living and working in proximity to you, and since they're humans with free choice, they tend to move to places that are nice for them to live in, which not surprisingly usually doesn't include economic backwaters.