A Study to Test How Well BAY 3670549 Works and How Safe it is in Patients With Atrial Fibrillation

The main goal of this study is to find out how well BAY 3670549 works, how safe it is, how well people can tolerate it, and how the body handles the medicine. The study will compare BAY 3670549 to a placebo (a dummy treatment with no active medicine) in people with AF who need a treatment called electrical cardioversion. Electrical cardioversion is a procedure that helps the heart return to a normal rhythm. In this study, each participant will get a single intravenous (IV) infusion of either BAY 3670549 or a placebo. Participants will then be observed to see whether the heart rhythm returns to a normal rhythm. If it does not, electrical cardioversion can still be performed as planned. The study will look at how many participants return from AF to a normal rhythm, without needing electrical cardioversion and how long it takes. It will also show how many participants experience medical problems after treatment and how BAY 3670549 move into, through and out of the participants' body. The total duration of the study for an individual participant may be up two months. The findings from this study may contribute to the development of a new treatment option for people with AF.