Autonomic changes and heart rate variability in children with neurocardiac syncope

Area of Science:

• Pediatric Cardiology
• Autonomic Neuroscience
• Clinical Physiology

Background:

• Neurocardiac syncope is a frequent cause of fainting in children, yet its underlying autonomic mechanisms remain unclear.
• Understanding autonomic function is crucial for diagnosing and managing pediatric syncope.
• Previous research has not fully elucidated autonomic differences in children experiencing syncope.

Purpose of the Study:

• To assess resting autonomic function in children with neurocardiac syncope.
• To evaluate autonomic responses during head-up tilt-table testing in these children.
• To compare autonomic function between pediatric syncope patients and healthy controls.

Main Methods:

• Noninvasive autonomic function tests (Valsalva, handgrip, deep breathing) and 24-hour heart rate variability (HRV) were used.
• Head-up tilt-table testing was performed, monitoring heart rate and blood pressure.
• Data from syncope patients were compared with age-matched healthy volunteers.

Main Results:

• No significant differences were found in resting noninvasive autonomic function tests.
• Some heart rate variability (HRV) measures showed a trend towards significance (p < 0.10).
• Tilt testing revealed significant differences in RR intervals and their standard deviation between syncope patients and controls, particularly before syncope, suggesting altered autonomic tone.

Conclusions:

• Children with neurocardiac syncope exhibit autonomic abnormalities during tilt-table testing.
• These abnormalities suggest increased sympathetic or decreased parasympathetic tone preceding syncope.
• Certain HRV measures may serve as noninvasive predictors of positive tilt-table test results in pediatric syncope.