Diagnosis of postoperative atrial fibrillation using smartwatch monitoring after cardiac surgery: protocol for the FAWATCH single-centre, open-label, randomised controlled trial

Introduction Postoperative atrial fibrillation (POAF) remains the most frequent arrhythmic complication after cardiac surgery, with most episodes occurring after discharge from the intensive care unit (ICU) when continuous rhythm monitoring is no longer routinely available. Early detection of POAF is clinically relevant and influences long-term cardiovascular outcomes. Wearable devices combining photoplethysmography technology with single-lead ECG capability offer a potential solution for continuous rhythm monitoring in conventional surgical wards. However, their effectiveness and feasibility in the immediate postoperative in-hospital setting remain insufficiently evaluated. The FAWATCH trial aims to determine whether smartwatch-based rhythm monitoring improves POAF detection within the first 5 days after ICU discharge compared with standard. Methods and analysis FAWATCH is a single-centre, open-label, randomised controlled trial conducted in the cardiac surgery department of Amiens-Picardie University Hospital. Adult patients undergoing cardiac surgery with cardiopulmonary bypass and transferred to the conventional surgical ward within 96 hours are eligible for inclusion. Patients are randomised in a 1:1 ratio using a centralised, computer-generated block randomisation sequence implemented through secure electronic software. Randomisation is stratified by age (>65 years), diabetes status and type of surgery (valvular, coronary or combined procedures). Participants are allocated to either standard care or smartwatch-based monitoring using a conformity European-marked single-lead ECG device (ScanWatch, Withings Move ECG, Withings, France). In the intervention group, patients wear the smartwatch continuously for 5 days and perform on-demand single-lead ECG recordings when alerted or symptomatic, with confirmation by standard 12-lead ECG. In the control group, POAF is diagnosed exclusively by a 12-lead ECG performed on clinical suspicion, as per routine practice. The primary outcome is the incidence of POAF within 5 days following ICU discharge. Secondary outcomes are the proportion of asymptomatic POAF, the association between left atrial reservoir strain and POAF occurrence, the feasibility of smartwatch monitoring, recurrence of POAF and major adverse cardiovascular events at 30 days, 3 months and 6 months. Recruitment began in January 2023, and the trial is currently ongoing, with 258 patients enrolled to date. Ethics and dissemination Ethical approval has been obtained from the Institutional Review Board of Amiens-Picardie University Hospital (IRB-ID: 2022-A00497-36). All participants provide written informed consent in accordance with French regulations for interventional clinical research. The study’s results will be disseminated through peer-reviewed publications and presentations at national and international conferences. Trial registration number NCT05573633 .