How do you calculate QTc intervals in patients being admitted for AAD drug loading who remain in atrial fibrillation or atrial flutter?   

We measure 10 R-R intervals and the corresponding 10 QT intervals, average each of them, and then calculate the QTc. Bazett’s formula is commonly used, but is probably less accurate than other correcting formulae, particularly for patients actively in atrial fibrillation. We often use the Fram...

I have been using the Fridericia formula in patients with AF with rapid rates. Fridericia formula is more accurate at estimating QTc at increased heart rates.

I agree with other answers, every formula falls apart as HRs differ from 60 bpm, though some, like Fridericia, are a little better than others. The key is looking after cardioversion. If you are concerned, consider DCCV after 1-2 doses into the 5-6 dose load for dose adjustment. Here is a visualiza...