Clinical Research Directory

Key Inclusion Criteria: * Proven paroxysmal atrial fibrillation or undergoing first-time elective electrical (direct current) cardioversion for persistent atrial fibrillation, or second-time elective electrical (direct current) cardioversion. * Baseline AF Criteria: To qualify for treatment, each participant must have during the 28-day baseline period an AFB greater than 5% and one of the following qualifying events: 1) 2 continuous AF episodes (LEAF) of 5 hours or longer; or 2) 2 rolling 24-hour periods in which cumulative AF duration is 5 hours or longer; or 3) 1 continuous AF episode (LEAF) of 5 hours or longer plus 1 rolling 24-hour period in which cumulative AF duration is 5 hours or longer * Must have failed at least one prior therapy for AF * Must have an AFSS greater than 3. * CHA₂DS₂-VASc score of 1 or more for males and 2 or more for females and be on oral anticoagulant for at least 3 weeks prior to receiving the study medication. * For participants with heart failure: NYHA Class I or II heart failure. Key Exclusion Criteria: * NYHA Class 3 or 4 heart failure. * MI, ischemic stroke, or any clinically relevant venous thromboembolism within 3 months of screening. * Unstable angina, percutaneous transluminal coronary angioplasty (PTCA), or CABG within 3 months of screening. * Prolonged QTcF Interval with a normal QRS duration (\>500 ms with QRS ≤120 ms). * Persistent AF (≥7 consecutive days or episodes \>23 hours). Those presenting with persistent AF at screening are eligible if they are scheduled to undergo first-time elective cardioversion, or second-time cardioversion * Recent treatment with rhythm control medications (Class I or III Singh-Vaughan Williams) within five half-lives before screening (rate control drugs permitted) and amiodarone within 3 months prior to screening. * Cardiac ablation procedures within 30 days of screening or participants who have scheduled an ablation procedure * Severe end-organ disease