Using WHOOP Fitness Band to Measure Heart Health Variability Before and After Surgery

The goal of this observational study is to use the WHOOP device to measure heart rate variability (HRV) in patients with coronary artery disease (CAD) before and after they have CABG (coronary artery bypass graft) surgery. The main questions it aims to answer are: * Can changes in HRV, measured by the WHOOP device, help predict how well patients with CAD will recover after CABG surgery? * Can HRV changes during the hospital stay give doctors useful information about the patient's recovery? Participants will: * Wear the WHOOP device before and after their CABG surgery to measure HRV. * Share their health information to help researchers see how changes in HRV are connected to recovery. This study will help find out if the WHOOP device can be used as a medical tool to track recovery in patients with CAD after CABG surgery.