My husband is 34 with Af. He was in ICU for 2 days then to main floor for 1 then released. He is under supervision  and currently taken Ritmaland PP meds. He was fine for 2 weeks with no fibulation but all the sudden every night this week he is waking up in AF about 3:30 am , It last any where from 30 mins to an hour.  What is causing this and why at night when he is sleeping.

Summarized question: What causes sudden atrial fibrillation while sleeping?