Observations on the arterial baroreflex in neurally mediated vasodepressor syncope

The arterial baroreflex was studied in subjects who had recently had an episode of vasodepressor syncope. This was determined using 2-3 mcg/kg intravenous boluses of phenylephrine and assessing the bradycardic response. The values were measured in ms/mmHg and expressed as the angular coefficient of...

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Bibliographic Details
Published in:Clinical autonomic research 1994-12, Vol.4 (6), p.307-309
Main Authors: Lagi, A, Cipriani, M, Fattorini, L, Paggetti, C, Macerata, A
Format: Article
Language:English
Subjects:
Adolescent
Adult
Baroreflex - physiology
Bradycardia - physiopathology
Female
Humans
Male
Neurons - physiology
Pressoreceptors - physiology
Regression Analysis
Syncope - physiopathology
Time Factors
Vascular Resistance - physiology
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Summary:The arterial baroreflex was studied in subjects who had recently had an episode of vasodepressor syncope. This was determined using 2-3 mcg/kg intravenous boluses of phenylephrine and assessing the bradycardic response. The values were measured in ms/mmHg and expressed as the angular coefficient of the regression line between the increase in R-R interval on the electrocardiograph and the systolic arterial pressure. In subjects examined immediately after the vasodepressor syncope episode the bradycardic response was much more marked than in controls (p < 0.01) and in the subjects themselves 6 months after the episode, provided that they were symptom-free (p < 0.01). It is concluded that in vasodepressor syncope there is a phase in which the baroreflex is highly sensitive and that this is due not to a lowering of the stimulation threshold but to a gain in the efferent arc, which explains a 'vagotonic' response.
ISSN:0959-9851
1619-1560
DOI:10.1007/BF01821530