BoxX-NoAF Clinical Trial

Inclusion Criteria: * Planned and clinically indicated for cardiac surgical procedure requiring cardiac bypass and opening of the pericardium * Age ≥ 65 years and CHA2DS2-VASc ≥ 3 Exclusion Criteria: * Documented history of atrial fibrillation or atrial flutter anytime prior to the cardiac surgery * Prior procedure involving opening the pericardium or entering the pericardial space * Patients undergoing off-pump surgery * Prior LAA occlusion, exclusion, or removal (surgical or percutaneous) * Presence of a permanent pacemaker * Infiltrative cardiomyopathies (i.e. amyloidosis) * Planned cardiac surgical procedure using non-sternotomy approaches * Patients whose planned procedure is a heart transplant or implantation of any long-term ventricular assist devices * Presence of ventricular arrhythmia * Active endocarditis * NYHA Class IV heart failure symptoms * Preoperative need for an intra-aortic ballon pump or intravenous inotropes * Active systemic infection at the time of cardiac surgery requiring antibiotics * Known allergy to Nitinol or nickel sensitivity * Known medical condition with expected survival of less than 1 year * Other comorbidities that in the Investigator's opinion make the subject unsuitable candidate to complete the protocol required intervention or visits * Current enrollment in an investigation or trial or an investigational devices or investigational drug that would interfere with this trial * Mental impairment or other psychiatric conditions which may not allow the patient to understand the nature, significance, and scope of the trial. * Pregnancy * Known severe symptomatic carotid disease