This study focuses on people who have atrial fibrillation and are scheduled for or underwent left atrial appendage closure (LAAC). The purpose of the study is to better understand differences between 2 ways of imaging the heart after LAAC. The current standard of care for patients who underwent LAAC is to have follow-up TEE (a type of ultrasound) for device surveillance. TEE is an ultrasound of the heart that is done by placing a probe in the esophagus under conscious sedation. It does not use contrast but can be cumbersome to patients. Cardiac CTA is a non-invasive imaging modality that involves the use of certain types of x-rays, contrast (dye) and computers to generate accurate images of the heart. Participants in this study will undergo both TEE and CTA on the same day, 90 days after their LAAC procedure.