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

Lee, Kwang Ho; Chung, Chin Sang; Song, Hee Jung; Cho, Soo Jin; Kim, June Soo; Seo, Jung Don; Lee, Won Ro; Lee, Sang Chol

Abstract

BACKGROUND: 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 ultrasonogra-phy (TCD) in patients with neurocardiogenic syncope or presyncope.
METHODS
Thirty-three patients with a history of recurrent syncope or presyncope of unknown origin were evaluated using HUT for 30 minutes (baseline tilt test), fol-lowed by an infusion of intravenous isoproterenol if needed. Systolic (SV) and diastolic velocities (DV) of middle cere-bral artery were continuously monitored by TCD. Positive responses were defined as presyncope or syncope with hypotension, bradycardia, or both.
RESULTS
Five patients had positive responses during baseline tilt and 14 patients dur-ing 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.
CONCLUSIONS
TCD shows different patterns of changes in cerebral hemody-namics during HUT. TCD can be used to investigate the pathophysiology of neurocardiogenic syncope.