Inclusion Criteria:  Enrollment in NCT03214601 based on presence of a thoracic aortic aneurysm, penetrating atherosclerotic ulcer, or chronic type B dissection that would require coverage of the brachiocephalic trunk and/or left carotid if a non-branching endograft were implanted Advanced heart failure with plan to treat with LVAD At least 18 years of age Patients enrolled prospectively must sign the informed consent form If patients underwent TCD monitoring during a previous RelayBranch procedure as part of routine clinical care, we will also incorporate their data in our analysis  Exclusion Criteria:  Skull defect or skull surgery that will preclude monitoring Known lack of TCD temporal acoustic window (if had TCD in past) Expected surgical position will preclude access to the patient's head for monitoring