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Changes of Cerebral Blood Flow during Head-up Tilt Test in Patients with Recurrent Syncope and Presyncope.

B a c k g r o u n d: The changes of cerebral hemodynamics during syncope have not been fully evaluated. We investigated the changes in the cerebral blood flow velocity during head-up tilt test (HUT) using transcranial Doppler ultrasonography (TCD) in patients with neurocardiogenic syncope or presyncope. M e t h o d s: Thirty-three patients with a history of recurrent syncope or presyncope of unknown origin were evaluated using HUT for 30 minutes (baseline tilt test), followed by an infusion of intravenous isoproterenol if needed. Systolic (SV) and diastolic velocities (DV) of middle cerebral artery were continuously monitored by TCD. Positive responses were defined as presyncope or syncope with hypotension, bradycardia, or both. R e s u l t s: Five patients had positive responses during baseline tilt and 14 patients during the isoproterenol infusion. During the baseline tilt test, there was a 86 ± 23% drop in DV and a 41 ± 34% drop in SV in patients with positive responses, and mean changes in those were less than 10% in patients with negative responses (p=.00, p=.00). During the HUT with an isoproterenol infusion, the TCD showed an 80 ± 18% drop in diastolic velocity in patients with positive responses, and a 47 ± 10% drop in patients with negative responses (p=.00), However, the change in systolic velocity did not differ. TCD showed three patterns during positive responses: loss of all flow, loss of end-diastolic flow, and a decrease in diastolic velocity. Loss of consciousness occurred in patients with loss of all flow or end-diastolic flow during positive responses. C o n c l u s i o n s: TCD shows different patterns of changes in cerebral hemodynamics during HUT. TCD can be used to investigate the pathophysiology of neurocardiogenic syncope. J Kor Neurol Ass 17(3):376 ~ 383, 1999