A good article that reviews the use of electrical cardioversion in converting patients that present in 48 hours with new onset atrial fibrillation.  They found no statistical difference in mortality with rhythm control vs rate control although there was a trend towards increased stroke rates in rhythm control which was countered by better quality of life in the same group.

Perhaps it would be worthwhile to have this conversation with the patient and if they want to proceed then shock them to get them back to NSR.