Related Experiment Videos
Baroreflex sensitivity in patients with vasovagal syncope
H L Thomson1, K Wright, M Frenneaux
1Department of Medicine, University of Queensland, Royal Brisoane Hospital, Australia.
Circulation
|January 21, 1997
Summary
Patients with vasovagal syncope exhibit reduced baroreflex sensitivity, specifically impaired cardiopulmonary baroreceptor function during lower body negative pressure. This finding suggests a potential mechanism contributing to fainting episodes in these individuals.
Area of Science:
- Cardiology
- Neuroscience
- Physiology
Background:
- Vasovagal syncope is a common condition characterized by a sudden drop in heart rate and blood pressure, leading to fainting.
- Baroreflex sensitivity plays a crucial role in maintaining cardiovascular stability.
- Previous studies suggest a potential link between reduced baroreflex sensitivity and vasovagal syncope, but the specific mechanisms remain unclear.
Purpose of the Study:
- To investigate and compare baroreflex sensitivity between patients with vasovagal syncope and healthy control subjects.
- To assess different components of baroreflex sensitivity, including cardiopulmonary and carotid baroreflexes.
Main Methods:
- The study included 30 patients with vasovagal syncope and 32 healthy controls.
- Cardiopulmonary baroreceptor sensitivity was evaluated using lower body negative pressure (LBNP) to measure changes in forearm vascular resistance.
- Carotid baroreflex sensitivity was assessed by measuring RR interval changes in response to manipulated carotid transmural pressure.
- Phenylephrine-induced baroreceptor sensitivity was determined by analyzing the relationship between RR interval and systolic blood pressure.
Main Results:
- During -10 mm Hg LBNP, patients with vasovagal syncope showed a decrease in forearm vascular resistance (0.7 +/- 11.6 U), unlike control subjects who exhibited an increase (8.3 +/- 6.2 U) (P = .002).
- No significant differences were found in phenylephrine baroreceptor sensitivity (11 +/- 7 ms/mm Hg vs. 14 +/- 6 ms/mm Hg; P = NS) or carotid baroreflex sensitivity (4 +/- 6 ms/mm Hg vs. 4 +/- 2 ms/mm Hg; P = NS) between the groups.
Conclusions:
- Patients with vasovagal syncope demonstrate impaired forearm vasoconstriction or paradoxical vasodilation during subhypotensive LBNP.
- This response suggests impaired cardiopulmonary baroreceptor inactivation or paradoxical activation.
- The findings are consistent with reduced cardiopulmonary baroreceptor sensitivity in individuals with vasovagal syncope.