Thank you for your question. Now, CIS people have a huge advantage in the HIM field due to the fact that EHRs are becoming standard in so many facilities. I work in a LTACH and we are in the middle of implementing a full EHR and it enloves so much IT/IS work that someone with that type of experience is greatly desirable.
If I had that type of background the first places I would entertain for possible employment would be the EHR software providers. There's always a need for development and conversion project implementers. Some of the few companies I'm familiar with are EPIC, Allscripts, HCS Interactant, Softmed, Healthland, and Horizon Patient Folder.
Please read this article to find out opportunities for education/certification options.
I hope that helps!