Cerebral blood flow velocity during tilt table test for pediatric syncope

Area of Science:

• Neurology
• Cardiology
• Pediatrics

Background:

• Neurocardiogenic syncope involves brain hypoperfusion due to hypotension and bradycardia.
• Transcranial Doppler studies show increased cerebral vascular resistance preceding or during syncope.

Purpose of the Study:

• To investigate cerebral blood flow velocity during tilt table testing in pediatric patients with neurocardiogenic syncope.
• To determine if a critical flow velocity reduction (>40%) predicts presyncopal symptoms.

Main Methods:

• 27 pediatric patients (8-18 years) underwent a 3-stage, 80-degree tilt table test.
• Transcranial Doppler measured right middle cerebral artery blood flow velocity.
• Positive tests defined by syncope/presyncope with ≥30% decrease in systolic blood pressure and/or heart rate.

Main Results:

• Mean cerebral blood flow velocity decreased significantly in syncope groups (I & II) before symptoms, with reductions of 48% and 45% respectively.
• A >40% reduction in mean cerebral blood flow velocity, independent of hypotension, correlated with presyncope latency (rho = -0.62).
• Group III (negative tests) showed no significant blood flow velocity changes.

Conclusions:

• A sustained >40% reduction in mean cerebral blood flow velocity predicts presyncopal or syncopal events in the absence of hypotension.
• Identifying this critical threshold during tilt table testing may allow for timely intervention to prevent syncope.