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Pathophysiology of syncope.

Roger Hainsworth1

  • 1Institute for Cardiovascular Research, University of Leeds, Leeds, LS2 9JT, UK. medrh@leeds.ac.uk.

Clinical Autonomic Research : Official Journal of the Clinical Autonomic Research Society
|October 14, 2004
PubMed
Summary
This summary is machine-generated.

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Fainting (syncope) occurs when blood flow to the brain drops. Vasoconstriction helps prevent fainting, but the switch to vasodilation is still unclear. Increasing plasma volume can help.

Area of Science:

  • Physiology
  • Cardiovascular Regulation

Background:

  • Syncope is a temporary loss of consciousness due to insufficient blood flow to the brain.
  • Blood pressure regulation relies on baroreceptor reflexes controlling vascular resistance and heart rate.
  • The precise mechanism triggering the shift from vasoconstriction to vasodilation during syncope remains an open question.

Purpose of the Study:

  • To explore the physiological mechanisms underlying syncope.
  • To investigate the factors influencing blood pressure regulation during stress.
  • To understand the triggers for the switch in vascular tone leading to syncope.

Main Methods:

  • Review of physiological responses to gravitational and other stresses.
  • Analysis of baroreceptor reflex roles in blood pressure control.

Related Experiment Videos

  • Examination of factors contributing to syncope susceptibility.

    • Main Results:

    • Reduced cerebral blood flow (below 50% of normal) causes syncope.
    • Effective vasoconstriction is key to preventing syncope; heart rate changes are less significant.
    • Factors like upright posture, heat, dehydration, and emotional stress increase syncope risk.
    • Plasma volume plays a crucial role in preventing syncope.

    Conclusions:

    • The shift from vasoconstriction to vasodilation, leading to syncope, is likely mediated by a cerebral signal, not cardiac receptors.
    • Interventions increasing plasma volume, such as salt loading and exercise, can clinically benefit individuals prone to syncope.