Abstract
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.
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Lagi, A., Cipriani, M., Fattorini, L. et al. Observations on the arterial baroreflex in neurally mediated vasodepressor syncope. Clinical Autonomic Research 4, 307–309 (1994). https://doi.org/10.1007/BF01821530
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DOI: https://doi.org/10.1007/BF01821530