Inclusion Criteria1. Male or female age ≥18 years.
2. Isolated CABG or valve replacement/repair +/- CABG performed at the index surgical procedure.
3. At elevated risk of stroke and for having POAF/AFL, defined as having a CHA2DS2-VASC (congestive heart failure, hypertension, age ≥75 years (2 points), diabetes mellitus, previous stroke/transient ischemic attack (TIA) (2 points), vascular disease, age 65-74 years, sex class (female)) score of ≥4 or ≥2 with at least 1 of the following risk factors for developing POAF/AFL:
(i) Chronic obstructive pulmonary disease; (ii) Sleep apnea; (iii) Impaired renal function (defined as creatinine clearance <60 ml/min/1.73m2); (iv) Echocardiographic evidence of at least mild left atrial enlargement (defined as ≥41 mm on M-mode, ≥59 ml or ≥29 mL/m2 on biplane volume assessment from an echocardiogram performed within 12 months of study enrollment); (v) Elevated body mass index (defined as BMI ≥30); (vi) Combined surgery (CABG + valve repair/replacement).
4. Able to provide written informed consent.
Exclusion Criteria1. Atrial fibrillation or flutter at the time of randomization.
2. Known previous history of AF/AFL, diagnosed pre-operatively (note: documentation of a history of AF/AFL without accompanying rhythm proof will suffice).
3. Documentation of continuous AF/AFL for ≥24 hours during the in-hospital stay for the index cardiac surgery.
4. Subjects who, at the discretion of the treating cardiac surgery team, would be treated and discharged with oral anticoagulation due to POAF/AFL.
5. Mechanical valve replacement.
6. Current or anticipated treatment with oral anticoagulation for indications other than AF/AFL.
7. Hospitalization for ≥10 days (for the index cardiac surgery, with day #0 being the day of surgery).
8. Planned discharge from hospital with a type IC or III anti-arrhythmic drug.
9. Having received >5 grams of IV and/or oral amiodarone during hospitalization for the index cardiac surgical procedure.
10. Women of childbearing potential (WOCBP).
11. History of percutaneous or surgical left atrial ablation for AF.
12. Presence of a cardiac implantable electronic device with a functioning atrial lead (pacemaker, implantable cardioverter defibrillator, or cardiac resynchronization device).
13. Presence of an implantable loop recorder.
14. History of left atrial appendage ligation, removal, or occlusion.
15. Subjects with known allergies or hypersensitivities to adhesives or hydrogel.
16. Inability to provide written informed consent.
17. Current or anticipated participation in another randomized controlled trial in which the interventional drug or device is known to affect the incidence of the primary or secondary outcomes of this study.