after you join the study, you are assigned by a computer to receive either the test medication BAY 3670549 or a matching placebo. the assignment is done without you or the study staff knowing which one you receive.

before the infusion starts, clinical staff measure your vital signs, perform an electrocardiogram (ecg) to record your heart rhythm, and collect blood samples for laboratory tests. these measurements provide a reference point for later comparisons.

you receive a single intravenous infusion. if you are in the test group, the infusion contains BAY 3670549 at a dose of 00 mg, prepared as a powder for solution for infusion. if you are in the placebo group, the infusion contains an inert solution with no active drug. the infusion is given once, over the period specified in the study protocol.

while the infusion is running and for at least three hours after it starts, you are continuously monitored with an ecg. the goal is to observe whether your heart rhythm changes from atrial fibrillation to sinus rhythm and stays in sinus rhythm for at least one minute. this observation is made before any rescue therapy or other standard cardioversion treatment is used.

at the end of the infusion, a blood sample is taken to measure the plasma concentration of BAY 3670549. this helps determine how much of the medication is present in your bloodstream.

throughout the infusion and the monitoring period, clinical staff watch for any treatment‑emergent adverse events (teaes), which are any new or worsening medical problems that occur after the study medication is given. any such events are recorded and evaluated.

after the three‑hour monitoring window and any required follow‑up assessments, your participation in this phase of the study ends. the collected data are used to assess the efficacy and safety of BAY 3670549 compared with placebo.