Control Group. Patients with a stable TAA or PAU who do not require surgery are monitored in the outpatient clinic as standard of care. In this study, these patients will be given information about our study and will be asked to be included in our investigation. Once consent of the patients is confirmed, participants will undergo BP and HR measurements, ECG, blood tests, and one non-invasive MRI scan, at baseline. One year (between a window of 275 - 455 days) after baseline, the participants will undergo additional observations; non-invasive MRI study, BP and HR measurements, ECG and blood tests.