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Changes in heart rate variability during fainting.

Robert Sheldon¹, Kenneth Riff

¹Cardiovascular Research Group, University of Calgary, Calgary, Alberta T2E 0A1, CanadaBrady Research Group, Medtronic, Inc., Minneapolis, Minnesota 55401.

Chaos (Woodbury, N.Y.)

|October 1, 1991

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Fainting may result from a breakdown in dynamic physiological mechanisms regulating heart rate. Tilt table tests reveal significant heart rate changes during fainting, indicating altered vagal nerve activity.

Area of Science:

Cardiology
Physiology
Autonomic Nervous System Function

Background:

Heart rate variability (HRV) studies offer insights into dynamic physiological mechanisms.
Fainting (syncope) may arise from a failure of these regulatory mechanisms.
Understanding syncope mechanisms is crucial for clinical management.

Purpose of the Study:

To investigate the physiological mechanisms underlying fainting using heart rate variability.
To analyze changes in heart rate during induced syncope.
To explore the role of efferent vagal nerve traffic in syncope.

Main Methods:

Utilizing tilt table testing to reliably induce syncope in susceptible individuals.
Performing power spectral analysis of heart rate variability.

Related Experiment Videos

Monitoring heart rate changes and sinus node discharge during tilt tests.

Main Results:

Tilt table testing successfully induced syncope.
Significant alterations in heart rate were observed during fainting.
A loss of high-frequency components in HRV and progressive sinus node slowing occurred.
These changes suggest alterations in efferent vagal nerve activity.

Conclusions:

Fainting is associated with marked changes in heart rate variability.
Altered efferent vagal nerve traffic appears to be a key factor in syncope.
Further research into these mechanisms can elucidate normal cardiovascular regulation.