Sorry about your baby having some heart issues and too possible CF. I have twins with CF. First of all, if there is a belly distention that is not making your baby "want to eat" (from feeling full all the time), and there is significant bowel problems, then you can try a glycerin suppository to help with gas build up and possibly stool back up. If your baby does have CF, once started on digestive enzymes, this will clear up some issues for you. It's truely medical miracle medicine.
Does your baby have orange or frothy yellow stools? This will be a indication of digestive problems that occur in CF individuals.
I tend to not say too much due to different individuals having different genotype's and can have mild to severe symptoms. My twins have the most comon genotype which cause a middle of the road type of symptoms. A diagnosis must be made first in your case, and the sooner the better to know. Ask doctor to recomment a CF care center for the test for best results. It's only a little over 100 dollars and is covered by insurance.
Hope this helps and let me know if you have any other questions.