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Effects of calf venous capacitance initiation rate on tolerance to lower body negative pressure in women with and without vasovagal syncope (858.5)
Author(s) -
Skoog Johan,
Lindenberger Marcus,
Zachrisson Helene,
Länne Toste
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.858.5
Subject(s) - medicine , presyncope , vasovagal syncope , lower body , stroke volume , cardiology , heart rate , baroreceptor , hypovolemia , blood pressure , anesthesia , blood volume , central venous pressure , reflex
Objective: Lower limb venous blood pooling has been considered an important factor in the pathophysiology of vasovagal syncope (VVS). However, not only the pooled volume, but also the rate by which the hypovolemic stimulus is instituted may be of importance. The aim of this study was to determine the influence of calf venous capacitance (V cap initiation rate on tolerance to lower body negative pressure (LBNP) in women with and without VVS. Design and Methods: Graded LBNP to presyncope was used to determine LBNP tolerance index (LTI) in 13 young women with VVS and 15 matched controls. During LBNP, V cap and the initiation rate of V cap was evaluated with volumetric technique and overall cardiovascular responses were measured. Results: No differences in V cap were found. In controls, the initiation rate of V cap was negatively related to LTI (r = ‐0.54, P < 0.05), and a rapid initiation of V cap was related to a lesser decline in stroke volume (r = ‐0.68, P < 0.05) and pulse pressure (r = ‐0.52, P < 0.05) during LBNP. In VVS, the initiation rate of V cap was positively related to LTI (r = 0.82, P < 0.01), and a slower initiation was related to lesser decline in stroke volume (r = 0.61, P < 0.05). Conclusions: In healthy women, a rapid institution of V cap was related to a more effective cardiovascular regulation and a higher LTI, possibly explained by greater baroreceptor deactivation due to a more rapid onset of the hypovolemic stimulus. However, the opposite was presented in VVS women, highlighting fundamental differences in cardiovascular regulation. Grant Funding Source : Supported by the Swedish Heart and Lung Foundation