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Abnormal reflex venous function in patients with neuromediated syncope
D E Manyari1, S Rose, J V Tyberg
1Cardiovascular Research Group, University of Calgary, Alberta, Canada.
Journal of the American College of Cardiology
|June 1, 1996
Summary
Patients with neuromediated syncope exhibit abnormal forearm venous responses to mental stress. This suggests that reflex control of veins may be crucial in the development of syncope.
Area of Science:
- Cardiovascular physiology
- Autonomic nervous system function
- Clinical neurology
Background:
- Neuromediated syncope is associated with paradoxical arterial vasodilation during stress.
- Diminished venous return (preload) is implicated in syncope reflex responses.
- Mental stress may trigger abnormal venodilation in syncope patients.
Purpose of the Study:
- To compare forearm reflex venous responses to mental arithmetic stress.
- To investigate differences between patients with neuromediated syncope and healthy individuals.
Main Methods:
- Studied 12 healthy subjects and 27 patients with neuromediated syncope.
- Utilized mental arithmetic stress tests.
- Assessed forearm venous pressure-volume relations using radionuclide plethysmography.
Main Results:
- Both groups showed similar increases in heart rate and blood pressure during stress.
- Normal subjects exhibited forearm venoconstriction (13%).
- Patients with syncope showed a varied response: 52% lacked normal vasoconstriction, with some displaying paradoxical venodilation.
Conclusions:
- Patients with neuromediated syncope display an abnormal spectrum of forearm venomotor responses to mental stress.
- Abnormal reflex venous control may contribute significantly to the pathogenesis of neuromediated syncope.