Participants will be randomized and assigned to one of the following 2 treatment arms in a ratio of 5:1:~Arm 1: HSY244 intravenous infusion Arm 2: Placebo intravenous infusion~The study consists of a screening period of up to 3 days and a treatment period of 5 days. After confirming eligibility and pre-dose assessments are completed on Day 1, study administration will occur and participants will be monitored for cardioversion to sinus rhythm. During the treatment period, participants will be evaluated for efficacy, safety, tolerability, and pharmacokinetics.
The purpose of this study is to evaluate the efficacy, safety, tolerability, and pharmacokinetics of HSY244 in participants with atrial fibrillation (AF), with and without heart failure (HF).