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Impaired endothelin-1 release in tilt-induced syncope
M White1, P Cernacek, M Courtemanche
1Department of Medicine, Montreal Heart Institute, Quebec, Canada.
The American Journal of Cardiology
|March 4, 1998
Summary
Neurocardiogenic syncope involves unclear neurohumoral events. Patients with syncope show increased adrenomedullary activation and reduced vagal tone, with no significant endothelin-1 increase, impacting orthostatic stress tolerance.
Area of Science:
- Cardiology
- Neuroscience
- Endocrinology
Background:
- Neurocardiogenic syncope's neurohumoral mechanisms are not fully understood.
- Simultaneous assessment of hormones and autonomic balance during tilt-induced syncope is incomplete.
Purpose of the Study:
- To investigate neurohumoral and autonomic changes during head-up tilt test in patients experiencing syncope.
- To compare hormonal responses (catecholamines, endothelin-1, angiotensin-II) and heart rate variability between syncope and control groups.
Main Methods:
- Forty-six healthy subjects underwent a 60-degree head-up tilt test.
- Hemodynamics, hormone levels (catecholamines, endothelin-1, angiotensin-II), and heart rate variability were measured.
- Fourteen subjects experienced syncope during the test.
Main Results:
- Subjects with syncope showed greater catecholamine increases and less high-frequency heart rate variability.
- Endothelin-1 levels did not increase in the syncope group during tilt.
- Angiotensin-II increased only in the control group.
Conclusions:
- Patients with syncope exhibit heightened adrenomedullary activation and blunted vagal tone.
- The lack of endothelin-1 response may impair orthostatic stress tolerance.
- These findings clarify neurohumoral events in neurocardiogenic syncope.