I can think of 2 related possibilities:
1) If you can export out of your current registration system most or all of the recurrent patients, do that and import into AC. I think this is what he was talking about as far as mapping the catagories to AC.
2) Run dupicate registration systems. When a new patient comes in, the information is put into both systems. If you have many of the old patients from above, this is less burdensome.
3) Yes, you can have an interface created, but both expense and time would probably be reasons not to do that.
Another possibility is to only put telephone number in AC and all ofther information would go to "official" registration system. If you need to get in touch with a patient, having a telephone number would be nicer than having to switch systems to get info
