I too am taking Celexa for anxiety associated with Afib and Aflutter that I was diagnosed with 2 years ago. I was such a nervous wreck about my arrythmia all the time that I was not able to function and started having severe panic attacks. The Celexa has worked wonders for me. It helped break the vicious cycle that I was in of having an arrythmia attack, panicking about it which made the arrythmia worse, which made the anxiety worse and son on... I still notice if and when I have arrythmia, but I am not panicked about it anymore. I can acknowledge that it is happening and go on with my life.
I am also taking Rhytmol, Cardizem and Digoxin for my arrythmia and Celexa doesn't seem to affect the other drugs in any way.
I have not personally prescribed Celexa, but it belongs to a class of antidepressant medications that is believed to be relatively safe for the heart. As such, it may be useful for the treatment of anxiety/depression due to any cause. I would not say that any antidepressant or anti-aniety medication is specific for the treatment of anxiety asociated with arrhythmia, though.