The purpose of this study is to compare edoxaban to warfarin (with enoxaparin, if needed). It will see if edoxaban prevents stroke and other blood clotting problems as well and as safely as warfarin. People with atrial fibrillation (irregular heartbeat) might be able to join. Their doctors must plan to use shock to make their hearts beat normally. About 2200 people from different countries will join. They will have an equal chance of receiving either treatment. They are anticipated to be in the study for around 82 days. Tests will include physicals and finger-pricks. Participants will provide blood and urine samples.

The purpose of this study is to compare edoxaban (investigational drug) with warfarin and enoxaparin, to see if it is safe and effective in preventing stroke and other blood clot complications in subjects with atrial fibrillation whose doctors plan to treat them with an electrical cardioversion. It is expected that 284 sites will recruit 2200 subjects from North America, EU, Russia, Ukraine and Israel. Participants will be randomly allocated to receive either treatment with edoxaban, or treatment with warfarin, plus enoxaparin if required. Participants will have an equal chance of receiving either treatment. Participants will be in the study for a maximum of 82 days. Study procedures will include physical examinations, vital signs (pulse and sitting blood pressure), ECG (electrocardiogram), finger prick blood clotting tests, blood samples and urine samples.

The study is expected to show that edoxaban will provide comparable incidence rates to warfarin plus enoxaparin, the current standard treatment for both efficacy and bleeding.

Inclusion Criteria:

• Has signed informed consent
• Is older than minimum legal adult age (country specific)
• Has had ongoing AF lasting at least 48 hrs but <= 12 months (with or without valvular heart disease)
• Has treatment plan that includes for electrical cardioversion
• Has NVAF or other specific valvular heart diseases (eg, mitral valve prolapse, mitral valve regurgitation, and aortic valve disease)

Exclusion Criteria:

• Has AF that is transient or reversible
• Has contraindicated condition, ie, conditions considered to be formal indication for conventional anticoagulation
• Has a history of left atrial appendage (LAA) closure
• Has a known thrombus in LAA, the left atrial, left ventricle or aorta - or an intracardial mass
• Has had myocardial infarction (MI), stroke, acute coronary syndrome (ACS), or percutaneous coronary intervention (PCI) within the past 30 days
• Has any contraindication to anticoagulant agents
• Has had protocol-defined signs of bleeding or conditions associated with high risk of bleeding that would preclude participation
• Is receiving, or plans to receive during the study period, dual antiplatelet therapy (DAPT) or invasive procedures (other than routine endoscopy) in which bleeding would be anticipated
• Has received prohibited concomitant medication or therapy
• Has had protocol-defined signs of bleeding or high
• Has inadequate liver, kidney, and blood test results
• Received any investigational drug or device within the past 30 days or plans to during the study period
• Has reproductive potential and does not agree to take proper contraceptive measures
• Has active cancer requiring chemotherapy/radiation/major surgery within the next 3 months
• Has significant active concurrent medical illness or infection or life expectancy less than 6 months
• In the opinion of the investigator, is unlikely to comply with the protocol or complete the study, has had drug or alcohol dependence within the past year, or has any other condition that might place the participant at increased risk of harm
• Is a participant in the United States after January 2015 with creatinine clearance (CrCL) greater than 95 mL/minute

De-identified individual participant data (IPD) and applicable supporting clinical trial documents may be available upon request at https://vivli.org/. In cases where clinical trial data and supporting documents are provided pursuant to our company policies and procedures, Daiichi Sankyo will continue to protect the privacy of our clinical trial participants. Details on data sharing criteria and the procedure for requesting access can be found at this web address: https://vivli.org/ourmember/daiichi-sankyo/

Studies for which the medicine and indication have received European Union (EU) and United States (US), and/or Japan (JP) marketing approval on or after 01 January 2014 or by the US or EU or JP Health Authorities when regulatory submissions in all regions are not planned and after the primary study results have been accepted for publication.

Formal request from qualified scientific and medical researchers on IPD and clinical study documents from clinical trials supporting products submitted and licensed in the United States, the European Union and/or Japan from 01 January 2014 and beyond for the purpose of conducting legitimate research. This must be consistent with the principle of safeguarding study participants' privacy and consistent with provision of informed consent.