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