Cardiac output and vasodilation in the vasovagal response: an analysis of the classic papers
File(s)
Author(s)
Type
Journal Article
Abstract
The simple faint is secondary to hypotension and bradycardia resulting in transient loss of consciousness. According to Ohm’s law applied to the circulation, BP = SVR × CO, hypotension can result from a decrease in systemic vascular resistance (SVR), cardiac output (CO), or both. It is important to understand that when blood pressure (BP) is falling, SVR and CO do not change reciprocally as they do in the steady state. In 1932, Lewis, assuming that decreased SVR alone accounted for hypotension, defined “the vasovagal response” along pathophysiologic lines to denote the association of vasodilation with vagal-induced bradycardia in simple faint. Studies performed by Barcroft and Sharpey-Schafer between 1940 and 1950 used volume-based plethysmography to demonstrate major forearm vasodilation during extreme hypotension and concluded that the main mechanism for hypotension was vasodilation. Plethysmographic measurements were intermittent and not frequent enough to capture rapid changes in blood flow during progressive hypotension. However, later investigations by Weissler, Murray, and Stevens performed between 1950 and 1970 used invasive beat-to-beat BP measurements and more frequent measurements of CO using the Fick principle. They demonstrated that CO significantly fell before syncope, and little vasodilation occurred until very late in the vasovagal reaction Thus, since the 1970s, decreasing cardiac output rather than vasodilation has been regarded as the principal mechanism for the hypotension of vasovagal syncope.
Date Issued
2015-11-17
Date Acceptance
2015-11-01
Citation
Heart Rhythm, 2015, 13 (3), pp.798-805
ISSN
1556-3871
Publisher
Elsevier
Start Page
798
End Page
805
Journal / Book Title
Heart Rhythm
Volume
13
Issue
3
Copyright Statement
© 2016, Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000372367800027&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Life Sciences & Biomedicine
Cardiac & Cardiovascular Systems
Cardiovascular System & Cardiology
Heart rate
Blood pressure
Cardiac output
Stroke volume
Systemic vascular resistance
Orthostasis
Vasovagal syncope
Central blood volume
lower body negative pressure
BODY NEGATIVE-PRESSURE
HEAD-UP TILT
VASODEPRESSOR SYNCOPE
ATROPINE
Cardiac Output
Cardiology
Humans
Periodicals as Topic
Syncope, Vasovagal
Vasodilation
Cardiovascular System & Hematology
1102 Cardiovascular Medicine And Haematology
0903 Biomedical Engineering
Publication Status
Published