I have seen people cardiovert with the medicines who did not respond to the electrical cardioversion but I am not sure of the perecentage success rate, it differs among the different agents used, so I may not be very helpful there.

By the way, with regards to carrying around vit k to reverse the coumadin in case of an emergency,it is not really that helpful. Oral replacement takes a few days to work and even injected vit k can take up to a day to work, so if you are bleeding out somewhere, the ER or doc will give fresh frozen plasma which reverses it instantaneously.