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Sympathoadrenal imbalance before neurocardiogenic syncope
David S Goldstein1, Courtney Holmes, Steven M Frank
1Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1620, USA. goldstein@ninds.nih.gov
The American Journal of Cardiology
|December 31, 2002
Summary
Neuroendocrine changes, specifically a sympathoadrenal imbalance with elevated epinephrine, precede neurocardiogenic syncope. This imbalance correlates with vasodilation, suggesting a role in the loss of consciousness.
Area of Science:
- Cardiology
- Neuroendocrinology
- Human Physiology
Background:
- Neurocardiogenic syncope is a common cause of fainting.
- Understanding the triggers and physiological changes preceding syncope is crucial for effective management.
Purpose of the Study:
- To investigate neuroendocrine and hemodynamic alterations before syncope.
- To identify potential pathophysiological roles of these changes.
Main Methods:
- Serial plasma catecholamine measurements (epinephrine, norepinephrine) in patients with orthostatic intolerance.
- Tilt-table testing to induce syncope.
- Forearm blood flow and vascular resistance measurements using impedance plethysmography.
Main Results:
- Patients experiencing syncope showed marked increases in plasma epinephrine, significantly outpacing norepinephrine increases (sympathoadrenal imbalance).
- Forearm vascular resistance decreased before syncope, correlating with the epinephrine-to-norepinephrine ratio.
- Absence of sympathoadrenal imbalance and presence of vasoconstriction in patients who did not faint.
Conclusions:
- Sympathoadrenal imbalance, characterized by elevated epinephrine, precedes both tilt-evoked and spontaneous neurocardiogenic syncope.
- This imbalance is associated with skeletal muscle vasodilation, contributing to hemodynamic instability.
- Sympathoadrenal imbalance is a key factor in the pathophysiology of neurocardiogenic syncope.