The purpose of this study is assess the incidence of postoperative atrial fibrillation (POAF) within one week of surgery in patients who receive pre-surgical stellate ganglion blockade with liposomal bupivacaine, compared to those receiving a saline placebo, using continuous electrocardiographic monitoring via wearable ECG devices.

Inclusion Criteria:

• Adults aged ≥40 years scheduled to undergo isolated coronary artery bypass grafting will be eligible.
• Cases will also remain eligible if, after the initial surgical listing, additional procedures-such as valvular interventions or septal myectomy-are performed, OR if coronary artery bypass grafting (CABG) is listed as the primary intervention with other procedures noted as possible additional interventions.
• Cases will also remain eligible if additional procedures-such as left atrial appendage ligation, MAZE procedure, cryotherapy, or pulmonary vein isolation-are concomitantly listed with the CABG.

Exclusion criteria:

• Permanent atrial fibrillation
• Mechanical circulatory support implant or explant
• Procedures not requiring cardiopulmonary bypass
• Heart and/or lung transplant patients
• Active infection/sepsis
• Pre-operative anti-arrhythmic use (aside from beta-blockers).
• Participant has a known allergy to adhesives or hydrogels.
• Participant has a visible skin injury or broken skin at the location for study device placement.
• Participant does not have the competency to wear the device for the prescribed patching period.
• Participant has a neuro-stimulator, as it may disrupt the quality of ECG data.
• Participants who are pregnant. In accordance with Mayo Clinic's standard cardiac surgery protocol, all women of childbearing potential undergo routine preoperative pregnancy testing. Pregnancy status will therefore be confirmed prior to enrollment. Any participant with a positive pregnancy test will be deemed ineligible and will not be enrolled in the study.
• Participants who lack the capacity to provide informed consent will not be approached or enrolled in this study.