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Pathophysiological mechanisms underlying vasovagal syncope in young subjects
W Wieling1, A A Smit, C C de Jong-de Vos van Steenwijk
1Department of Internal Medicine, Academic Medical Centre, Amsterdam, The Netherlands.
Pacing and Clinical Electrophysiology : PACE
|August 1, 1997
Summary
Vasovagal fainting in young people involves early failure of vascular resistance responses. The primary cause is sympathetic withdrawal, impairing vasomotor tone in skeletal muscle blood vessels.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Function
Background:
- Vasovagal fainting is common in young individuals.
- The precise hemodynamic mechanisms initiating fainting are not fully understood.
- Fainting is not instantaneous, with precursors involving vascular responses.
Purpose of the Study:
- To investigate the early hemodynamic changes preceding vasovagal syncope.
- To identify the primary mechanism responsible for fainting in susceptible young subjects.
Main Methods:
- Hemodynamic monitoring in faint-prone young subjects.
- Analysis of vascular resistance and sympathetic outflow during syncope induction.
- Assessment of vasomotor tone maintenance.
Main Results:
- Early failure of vascular resistance responses was observed in faint-prone subjects.
- Sympathetic outflow withdrawal to skeletal muscle blood vessels was identified as a key mechanism.
- Impaired ability to maintain vasomotor tone contributes significantly to fainting.
Conclusions:
- Vasovagal fainting is preceded by a failure in vascular resistance.
- Withdrawal of sympathetic nervous system activity is the main driver of fainting.
- Understanding these mechanisms can inform strategies for managing vasovagal syncope.