Inclusion Criteria:
1. Age 18 years and over.
2. Provision of written informed consent.
3. Documented history of symptomatic AF (paroxysmal, persistent, or permanent) with a ventricular rate of ≥110 bpm.
- Documentation: electrocardiogram (ECG) tracing (including 12-lead ECG or ECG strip) showing AF with ventricular rate ≥110 beats per minute (bpm). This ECG documentation (anonymized with study Patient ID only) will be submitted to the Sponsor after screening and prior to randomization to confirm diagnosis of AF with RVR and eligibility to be randomized in the study. Patients who have undergone a prior ablation procedure for AF or for an AF-trigger must have documented AF with RVR post-ablation for study eligibility.
4. Documented history of repeated (at least 2 within the prior 12 months) and prolonged (at least 20 minutes) symptomatic episodes of AF with elevated (perceived or measured) heart rate (HR).
- Documentation: Patient description, other history, or medical records. Patients who have undergone a prior ablation procedure for AF or for an AF-trigger must fulfill this criterion post-ablation for study eligibility.
5. Receiving appropriate antithrombotic/anticoagulation therapy as per applicable national and/or local guidelines for AF management.
6. Women of childbearing potential must have a negative pregnancy test at Screening and agree to use at least 1 highly effective form of contraception from time of randomization until 7 days after the last administration of study drug and must be willing to discontinue from the study should they become or plan to become pregnant.
Exclusion Criteria:
1. Patients with a primary diagnosis of atrial flutter (typical or atypical) or atrial tachycardia. Patients with AF who have been observed to also experience atrial flutter within the same episode (i.e., "AFib/Flutter" or an admixture of AF and flutter within the same episode) are eligible.
2. History of any of the following within the last 6 months: Class 3 or 4 angina per Canadian Cardiovascular Society (CCS) criteria; ischemic chest pain during AF episodes; acute coronary syndrome, unless the patient has been successfully revascularized; coronary artery bypass grafting or open-chest valve surgery.
3. History of heart failure (HF) New York Heart Association (NYHA) classification ≥Class III within the last 3 months.
- The etiology of any HF should have been previously evaluated and addressed.
- HF with a reduced ejection fraction and/or HF with a preserved ejection fraction are acceptable.
4. History of hemodynamic instability during AF, i.e., symptoms or signs of severe hypotension, or syncope due to a pause upon conversion from AF to sinus rhythm (SR).
5. History of unexplained syncope.
6. History of, or ECG evidence at the screening visit, of: sick sinus syndrome, Mobitz II second- or third-degree atrioventricular (AV) block bradycardia (<40 bpm) or pauses >3 seconds during waking hours, without a pacemaker.
7. History of, or ECG evidence at the Screening visit, of: torsades de pointes, ventricular fibrillation, or ventricular tachycardia, Brugada syndrome, an antegrade conducting accessory bypass tract (e.g., Wolff-Parkinson-White or Lown-Ganong-Levine syndromes), or long QT syndrome.
8. History of stroke, transient ischemic attack or peripheral embolism within the last 3 months.
9. CHA2DS2-VASc score of >5.
10. Planned AF or AV node ablation within the next 3 months.
11. Uncorrected, severe aortic or mitral stenosis.
12. Hypertrophic cardiomyopathy with outflow tract obstruction.
13. History of sensitivity to verapamil or to any components of the investigational product.
14. History of recent or current chronic alcohol or drug abuse that, in the opinion of the Investigator, could impact the validity of the study results.
15. Currently participating in another drug or device study, or has received an investigational drug or device within 30 days prior to Screening.
16. Any other significant co-morbid condition that may negatively impact the patient's participation in the study or likely result in non-compliance.