Differences in Reactivity of Middle and Posterior Cerebral Artery in Patients with Neurocardiogenic Syncope

Park, Tai Hwan; Lee, Eun Hee; Yoon, Young Chul; Kim, Sang Wook

Abstract

BACKGROUND: Neurocardiogenic syncope (NCS) is the most common type of neurally mediated syncopes. Though presyncopal symptoms may represent hypoperfusion in posterior circulation, studies for evaluating the cerebrovascular response of posterior circulation in patients with NCS were scanty. We evaluated the cerebrovascular response of the posterior circulation using transcranial Doppler monitoring in patients with NCS.
METHODS
We measured the blood flow velocity (BFV) of the middle cerebral artery (MCA) and contralateral posterior cerebral artery (PCA) simultaneously in 11 patients with a diagnosis of NCS both at rest and during the head-up tilt test (HUT) for 5 minutes. The mean arterial pressure (MAP), pulse rate (PR), and end-tidal pCO2 (EtCO2) were also monitored. The obtained data were compared with those of 17 normal control subjects.
RESULTS
The syncope patients showed a significantly larger decline in BFV of PCA (P<0.05) and a larger increase in pulsatility indexes of MCA and PCA during HUT compared to those of control subjects. In control subjects BFV of PCA decreased less than those of MCA. On the contrary, in patients with NCS, those of PCA decreased more. These different regional cerebrovascular responses to HUT were accompanied with neither presyncopal symptoms nor decrease in MBP.
CONCLUSIONS
The regional cerebrovascular response to HUT in NCS patients was different in the PCA flow. Impairment of autonomic neural control of posterior circulation may play an important role in the pathophysiology of NCS.