The nausea could be the medication, or caused by the
CHF.
CHF does a lot of things to the body, and causes fluid build up in the oddest of places.
When I first had CHF, I had lots of nausea, and my abdomen hurt constantly. After I was started on Coreg, diltiaziem, lasix, and a host of other medications, the nausea took a couple of years to clear up. It seemed that the swelling was in my internal organs, as well as the rest of my tissues and the presure caused the the nausea and pain.