Background: Responses of cerebral blood flow to the postural unloading maneuver in aortic stenosis (AS) have not been described so far. Our aim was to assess effects of orthostatic stress test on changes of carotid and vertebral artery blood flow and transaortic gradients.

Methods: From consecutive 101 AS patients we selected 50 patients with severe isolated AS. Maximal and mean transaortic pressure gradients, as well as peak systolic blood-flow velocity (PSV) and end-diastolic velocity (EDV) in the common carotid artery, internal carotid artery and vertebral artery on both sides were measured by duplex ultrasound in the supine position and at 1–2 min after the assumption of the sitting position in patients with AS, and in stand­ing position in healthy controls.

Results: The orthostatic stress test induced significant decrease of carotid and vertebral arterial flow velocities in AS patients. Transaortic pressure gradients also dropped while the patients were sitting (p < 0.001). A history of syncope/presyncope was not associated with a significantly lower PSV and EDV in carotid and vertebral arteries in the upright position. In healthy controls, the velocities in carotid and vertebral arterial flow have been unchanged after maneuver reducing preload.

Conclusions: In AS patients, decrease of carotid and vertebral arterial flow velocities and transaortic gradients in the sitting position were observed. Orthostatic test position does not ap­pear to be associated with a history of syncope/presyncope in patients with severe isolated AS, de­spite a simultaneous drop of transvalvular pressure gradient.