This study aims to investigate whether a quick, additional CT scan of the heart, performed immediately after a standard CT scan for pulmonary embolism, can effectively detect blood clots in the left atrial appendage (LAA) in patients with atrial fibrillation. Detecting these clots is crucial before certain heart procedures to prevent stroke. Currently, a different, more involved procedure (Transesophageal Echocardiography - TEE) is often used. This study will assess if this additional CT scan is feasible, meaning if it can provide clear enough images to identify LAA clots without needing more contrast dye. The study will involve 60 patients, half receiving an "ungated" CT scan and the other half a "gated" CT scan (timed with their heart rhythm). The results of these scans will not be used for immediate patient care during the study, but rather to evaluate the CT scan technique itself. There is no direct benefit to participants, but the information gained could lead to faster diagnosis and reduced unnecessary testing for future patients.