The Rhythm Evaluation for AntiCoagulaTion With Continuous Monitoring of Atrial Fibrillation (REACT-AF)

Inclusion Criteria: Male or female, 22-85 years of age. English speaking participants* Documented history of symptomatic or asymptomatic paroxysmal or persistent AF. The duration of AF must have been > 30 seconds as documented by an external monitor or present on 12-lead ECG. CHA2DS2-VASC score of 1-4 without prior stroke or Transient Ischemic Attack (TIA)** The participant is on a DOAC at the time of screening. Willing and able to comply with the protocol, including: Possession of a smartwatch-compatible smartphone (iPhone that supports the latest shipping iOS) with a cellular service plan Be willing to wear the Apple watch at least 14 hours a day Expected to be within cellular service range at least 80% of the time Willing and able to discontinue DOAC The participant is willing and able to provide informed consent. Exclusion Criteria: Valvular or permanent atrial fibrillation. Current treatment with warfarin and unwilling or unable to take a DOAC. The participant is a woman who is pregnant, nursing, or of child-bearing potential and is not on birth control. The participant is being treated with chronic aspirin, another anti-platelet agent, or chronic NSAIDS outside of current medical guidelines (e.g., primary stroke prevention in patients with atrial fibrillation, primary prevention of cardiovascular events, pain relief, fever, gout) and is unwilling or unable to discontinue use for the study duration. Existing cardiac rhythm device or indication for a permanent pacemaker, Implantable Cardioverter-Defibrillator (ICD) or Cardiac Resynchronization Therapy (CRT) device or planned insertable cardiac monitor. Any documented single AF episode lasting ≥ 1 hour on screening external cardiac monitor of >=6 days duration. Mechanical prosthetic valve(s) or severe valve disease. Hypertrophic cardiomyopathy. Participant needs Direct Oral Anticoagulation (DOAC) for reasons other than preventing stroke or arterial embolism resulting from AF (i.e., preventing Deep Vein Thrombosis (DVT) or Pulmonary Embolism (PE)) or needs permanent Oral Anticoagulant (OAC) (i.e., congenital heart defects, prosthetic heart valve). Participants deemed high risk for non-cardioembolic stroke (i.e., significant carotid artery disease defined as stenosis > 75%) based on the investigator's discretion. The participant is enrolled, has participated within the last 30 days, or is planning to participate in a concurrent drug and/or device study during the course of this clinical trial. Co-enrollment in concurrent trials is only allowed with documented pre-approval from the study manager; there is no concern that co-enrollment could confound the results of this trial. The participant has a tattoo, birthmark, or surgical scar over the dorsal wrist area on the ipsilateral side that the AFSW may be worn. The participant has a tremor on their ipsilateral side that the AFSW may be worn. Any concomitant condition that, in the investigator's opinion, would not allow safe participation in the study (e.g., drug addiction, alcohol abuse). Known hypersensitivity or contraindication to direct oral anticoagulants. Documented prior stroke (ischemic or hemorrhagic) or transient ischemic attack. Reversible causes of AF (e.g., cardiac surgery, pulmonary embolism, untreated hyperthyroidism). AF ablation does not constitute reversible AF. > 5% burden premature atrial or ventricular depolarizations on any given calendar day on pre-enrollment cardiac monitoring. History of atrial flutter that has not been treated with ablation (participants in atrial flutter and have been ablated are eligible for enrollment). Stage 4 or 5 chronic kidney disease. Conditions associated with an increased risk of bleeding: Major surgery in the previous month Planned surgery or intervention in the next three months. History of intracranial, intraocular, spinal, retroperitoneal, or atraumatic intra-articular bleeding Gastrointestinal hemorrhage within the past year unless the cause has been permanently eliminated (e.g., by surgery) Symptomatic or endoscopically documented gastroduodenal ulcer disease in the previous 30 days Hemorrhagic disorder or bleeding diathesis Need for anticoagulant treatment for disorders other than AF Required use of non-aspirin antiplatelet agents (i.e., Plavix) at time of enrollment Uncontrolled hypertension (Systolic Blood Pressure (SBP) >180 mmHg and/or Diastolic Blood Pressure( DBP) >100 mmHg) Spanish-only speakers may be included in the future at select sites where consent forms are appropriately translated. Congestive heart failure defined as: The presence of signs and symptoms of either right (elevated central venous pressure, hepatomegaly, dependent edema) or left ventricular failure (exertional dyspnea, cough, fatigue, orthopnea, paroxysmal nocturnal dyspnea, cardiac enlargement, rales, gallop rhythm, pulmonary venous congestion) or both, confirmed by non-invasive or invasive measurements demonstrating objective evidence of cardiac dysfunction and/or ejection fraction < 40%