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Cardiac output and sympathetic vasoconstrictor responses during upright tilt to presyncope in healthy humans
Author(s) -
Fu Qi,
Verheyden Bart,
Wieling Wouter,
Levine Benjamin D.
Publication year - 2012
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2011.224998
Subject(s) - presyncope , tilt (camera) , medicine , vasoconstrictor agents , cardiology , cardiac output , sympathetic nervous system , sympathetic activity , heart rate , blood pressure , hemodynamics , mathematics , geometry
Key points • Syncope is a common clinical condition occurring even in healthy people without manifest cardiovascular disease; we determined the role of cardiac output and sympathetic vasoconstriction in neurally mediated (pre)syncope. • Our data showed that a moderate fall in cardiac output with coincident vasodilatation occurred in the majority (64%) of the presyncopal subjects, while a marked fall in cardiac output, driven predominantly by a decrease in heart rate, with no changes in total peripheral resistance at presyncope, occurred in a smaller (36%) subset. • Sympathetic withdrawal occurred late, after the onset of hypotension. • Sympathetic vasoconstriction and baroreflex sensitivity during symptom‐free upright posture were well preserved and, thus, an intrinsic impairment of sympathetic neural control and vasomotor responsiveness was not the cause of neurally mediated (pre)syncope in this population. • These results help us better understand the mechanisms for syncope in humans.