Please take your wife to your family doctor right away. Atrial fibriallation needs to be investigated, does she have mitral valve prolapse or not? If I were in the clinic, I would recommend that your dear wife see a cardiologist for a complete blood work-up, a holter monitor, an EKG, and a med review. Atrial fibrillation can cause fluctuations in blood pressure which is dangerous. Medication may or not be able to be given depending on if she has a valve disorder but nonetheless, whe needs to get the afib under control. With regards to the meds given in ER yes there may be a rebound possibility. This is nothing to ignore. Assess, medicate, diet, lifestyle, but assessment by a cardiologist comes first. My best wishes to your wife.