Study Of The Blood Thinner, Apixaban, For Patients Who Have An Abnormal Heart Rhythm (Atrial Fibrillation) And Expected To Have Treatment To Put Them Back Into A Normal Heart Rhythm (Cardioversion)

Some people can develop an abnormal heart beat known as "Atrial fibrillation" or "AF" that puts them at risk of developing clots in the heart. Those clots can travel in the blood circulation to the brain and cause a brain attack ("a stroke"). To prevent those clots forming, blood thinners (anti-coagulants) are used. Apixaban is a blood thinner that works by stopping one of the blood substances required for clotting ("Factor Xa"). It is approved and used to prevent clots forming in people with "AF". Other established blood thinners work by stopping clotting substances being made, known as "Vitamin K antagonists" or "VKAs". An example of this type is Warfarin (Coumadin). The good effects of all blood thinners are preventing clots, and they may also have bad effects of increasing the chance of bleeding. People with "AF", abnormal heart beat, may benefit from changing it back to a normal regular rhythm, known medically as "cardioversion". When this is done, people are currently most commonly treated with a "VKA" blood thinner (e.g. warfarin). The purpose of this study is to assess the good and bad effects ("efficacy" and "safety") of apixaban compared with warfarin in people with "AF" in whom an early cardioversion is planned.


Eligibility Criteria:
Inclusion Criteria:

* Subjects with non-valvular atrial fibrillation (as documented by electrocardiogram (ECG) at Visit 1) indicated for cardioversion and initiation of anticoagulation in accordance with the approved local label. Subjects presenting with atrial flutter with no evidence of atrial fibrillation are not eligible for enrolment.
* Age ≥18 years (Age ≥ 19 years for Korea only and Age ≥ 20 years for Japan only).
* Evidence of a personally signed and dated informed consent document indicating that the subject (or their legally-recognized representative) has been informed of all pertinent aspects of the study.
* The subject is willing to provide contact details for at least one alternate person for study staff to contact regarding their whereabouts, should the subject be lost-to-follow-up over the course of the study. (Subject to IRB/IEC approval)
* Female subjects of childbearing potential must agree to use a highly effective method of contraception throughout the study and for at least 28 days after the last dose of assigned treatment. A subject is of childbearing potential if, in the opinion of the investigator, she is biologically capable of having children and is sexually active.
* Subjects who are willing and able to comply with scheduled visits, treatment plan, and other study procedures.

Exclusion Criteria:

* Subjects having taken more than 48 hours of an anticoagulant (oral and/or parenteral) immediately prior to randomization.
* Contraindications to apixaban or usual care (eg, VKA) in accordance with the approved local label.
* Severe haemodynamically compromised subjects requiring emergent cardioversion.
* Patients with hemodynamically significant mitral stenosis, mechanical or biological prosthetic valve or valve repair.
* Conditions other than atrial fibrillation that require chronic anticoagulation (eg, a prosthetic heart valve).
* Simultaneous treatment with both aspirin and a thienopyridine (eg, clopidogrel, ticlopidine, prasugrel) or simultaneous treatment with both aspirin and ticagrelor.
* Pregnant females; breastfeeding females; females of childbearing potential who are unwilling or unable to use a highly effective method of contraception as outlined in this protocol for the duration of the study and for at least 28 days after last dose of investigational product.
* Participation in other studies involving investigational drug(s) (Phases 1-4) within 30 days before the current study begins and/or during study participation. Note: Subjects cannot be randomized into this study more than once.
* Severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the subject inappropriate for entry into this study.
* Subjects who are investigational site staff members directly involved in the conduct of the trial and their family members, site staff members otherwise supervised by the Investigator, or subjects who are BMS/Pfizer employees directly involved in the conduct of the trial.