| Abstract: | Syncope is a short loss of consciousness caused by a transient decrease of global cerebral blood flow. Neurally mediated syncope is associated with vasodilatory response and bradycardia. The Doppler ultrasonography was used to evaluate changes of the basilar artery blood flow mean velocity and pulsatility index during orthostatic challenge and CO2 reactivity testing in patients with neurally mediated syncope and a negative result of the Tilt Test. Eighteen patients aged 20-40 years with a history of cerebral syncope and 10 healthy volunteers were qualified. RESULTS: There were no significant differences between syncope patients and controls in the basilar artery blood flow parameters in various body positions during normocapnia, hypocapnia and hypercapnia. Irrespective of body position, the reactivity index in patients with neurally mediated syncope was lower than that in controls, but not significantly. CONCLUSIONS: No significant pathology was found in cerebrovasoreactivity responses in the area supplied by the basilar artery, which suggests that cerebral autoregulation disorders cannot be the primary cause of neurally mediated syncope. |
