You might find something very close to your medication for GERD in this list:
https://www.drugs.com/drug-interactions/flecainide.html
Please remember that, although there may be no apparent contraindication, even a slight one, mentioned in this article, it doesn't follow that YOU don't do well on the combination, especially when the two medications chase one another down the gut within an hour or two. You may have to spread them out during the day.