REACT-AF is a multicenter prospective, randomized, open-label, blinded endpoint (PROBE design), controlled trial comparing the current Standard Of Care (SOC) of continuous Direct Oral Anticoagulation (DOAC) use versus time-delimited (1 month) DOAC guided by an AF-sensing Smart Watch (AFSW) in participants with a history of paroxysmal or persistent Atrial Fibrillation (AF) and low-to-moderate stroke risk.



Eligible Ages
Between 22 Years and 85 Years
Eligible Genders
Accepts Healthy Volunteers

Inclusion Criteria

  1. Male or female, 22-85 years of age. 2. English speaking participants* 3. 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. 4. CHA2DS2-VASC score of 1-4 without prior stroke or Transient Ischemic Attack (TIA)** 5. The participant is on a DOAC at the time of screening. 6. 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 7. Willing and able to discontinue DOAC 8. The participant is willing and able to provide informed consent.

Exclusion Criteria

  1. Valvular or permanent atrial fibrillation. 2. Current treatment with warfarin and unwilling or unable to take a DOAC. 3. The participant is a woman who is pregnant, nursing, or of child-bearing potential and is not on birth control. 4. 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. 5. 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. 6. Any documented single AF episode lasting ≥ 1 hour on screening external cardiac monitor of >=6 days duration. 7. Mechanical prosthetic valve(s) or severe valve disease. 8. Hypertrophic cardiomyopathy. 9. 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). 10. Participants deemed high risk for non-cardioembolic stroke (i.e., significant carotid artery disease defined as stenosis > 75%) based on the investigator's discretion. 11. 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. 12. The participant has a tattoo, birthmark, or surgical scar over the dorsal wrist area on the ipsilateral side that the AFSW may be worn. 13. The participant has a tremor on their ipsilateral side that the AFSW may be worn. 14. Any concomitant condition that, in the investigator's opinion, would not allow safe participation in the study (e.g., drug addiction, alcohol abuse). 15. Known hypersensitivity or contraindication to direct oral anticoagulants. 16. Documented prior stroke (ischemic or hemorrhagic) or transient ischemic attack. 17. Reversible causes of AF (e.g., cardiac surgery, pulmonary embolism, untreated hyperthyroidism). AF ablation does not constitute reversible AF. 18. > 5% burden premature atrial or ventricular depolarizations on any given calendar day on pre-enrollment cardiac monitoring. 19. History of atrial flutter that has not been treated with ablation (participants in atrial flutter and have been ablated are eligible for enrollment). 20. Stage 4 or 5 chronic kidney disease. 21. 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%

Study Design

Phase 3
Study Type
Intervention Model
Parallel Assignment
Intervention Model Description
Participants randomized (1:1) to the experimental arm (AFSW-guided DOAC) will only take DOAC for 30 consecutive days following a qualifying AF episode (i.e., greater than 1 hour) detected by the participants AFSW if no further AF is detected. Participants randomized to the standard of care arm will remain on continuous DOAC throughout the study.
Primary Purpose
Single (Outcomes Assessor)
Masking Description
Adjudication of safety events will be performed by a Clinical Endpoint Committee made up of blinded assessors. The Data Coordinating Center (DCC) blinded statistician(s) will also be blinded.

Arm Groups

ArmDescriptionAssigned Intervention
All participants randomized to the experimental arm will be provided with an AFSW that will be linked to the participants Apple watch and the secure REACT-AF app within the Eureka cloud. The AFSW will intermittently and passively assess for rhythm irregularities consistent with AF and notify the wearer and coordinating center if a threshold AF event has occurred.
  • Device: AFSW Guided DOAC
    The AFSW will intermittently and passively assess for rhythm irregularities consistent with AF and notify the wearer and coordinating center if a threshold AF event has occurred.
    Other names:
    • Apple Watch
Active Comparator
Continuous DOAC therapy
All participants randomized to the control arm will remain on previously prescribed FDA-approved DOAC regimen as indicated by current practice standards. These participants will continuously take DOAC through the course of the study as prescribed by the participants primary physician unless otherwise contraindicated. Participants in the control arm will also use the REACT-AF mobile app within the Eureka platform via Apple watch for study follow-up activities, but the participants will not receive an AFSW and any personally owned Apple Watch will not be loaded with the customized REACT-AF detection algorithm nor participant notification apps.
  • Drug: Continuous DOAC therapy
    DOACs will be prescribed to patients according to the treating healthcare provider(s) according to labeling instructions.
    Other names:
    • Oral Anticoagulation therapy

Recruiting Locations

Boston Medical Center
Boston, Massachusetts 02118
Laura Gavrilles

More Details

Johns Hopkins University

Study Contact

Nicole Odenwald

Detailed Description

REACT-AF is a prospective, unblinded, randomized (1:1 allocation), multi-center, investigational clinical trial of men and women aged 22-85 with a documented history of symptomatic or asymptomatic paroxysmal or persistent (AF) and a moderate risk of stroke measured by CHA2DS2-VASc score 1-4 (which stands for Congestive heart failure, Hypertension, Age ≥75 (doubled), Diabetes, Stroke (doubled), Vascular disease, age 65 to 74 and sex category (female)). Participants randomized to the experimental arm (on demand DOAC) will take the participants DOAC for 30 consecutive days following a qualifying AF episode (i.e., greater than1 hour) detected by the AFSW. Participants randomized to the standard of care (control) arm will remain on previously prescribed continuous DOAC throughout the study. A total of 5350 participants will be enrolled across up to 100 study sites targeting two-thirds academic and one-third private practices, with academic practices also enrolling from affiliated community sites. The investigators anticipate evaluating 7643 consented individuals with external monitoring to ensure that a low AF burden population will be randomized. Up to 200 participants may be enrolled at any one site, and participation will last up to 60 months.


Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.