Document Detail


Comparison of valve resistance with effective orifice area regarding flow dependence.
MedLine Citation:
PMID:  11423057     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Aortic valve resistance has been proposed to represent the severity of aortic stenosis because some studies observed that it was less affected by change in flow than the valve-effective orifice area, but this issue remains controversial. The objective of this study was to systematically analyze the theoretical and practical determinants of these parameters in relation to changes in flow. Valve area and resistance in different valves were studied in vitro in a pulse duplicator system at different flow rates and in vivo in 90 subjects referred to either exercise or dobutamine infusion. Theoretical analysis and experimental results both demonstrated a unique relation between resistance (RES), valve-effective orifice area (EOA), and flow rate (Q): RES = K x (Q/EOA(2)). Accordingly, in fixed stenoses or in mechanical valves, resistance increased markedly with flow rate both in vitro (+0.88 +/- 0.26%/% of flow increase) and in vivo (mechanical valves: +2.09 +/- 4.61, fixed stenotic valves: +0.59 +/- 0.32%/%), whereas valve area did not change significantly (<0.2%/%). In contrast, in valves with a flexible orifice (bioprostheses and some patients with aortic stenosis), resistance was less increased due to the increase in valve area. Thus, both from a theoretical and a practical standpoint, valve resistance is much more flow dependent than valve area, particularly in fixed stenoses. Situations in which resistance does not increase with flow rate are unpredictable and are found in flexible valves when there is a concomitant increase in valve area.
Authors:
C Blais; P Pibarot; J G Dumesnil; D Garcia; D Chen; L G Durand
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of cardiology     Volume:  88     ISSN:  0002-9149     ISO Abbreviation:  Am. J. Cardiol.     Publication Date:  2001 Jul 
Date Detail:
Created Date:  2001-06-25     Completed Date:  2001-07-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0207277     Medline TA:  Am J Cardiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  45-52     Citation Subset:  AIM; IM    
Affiliation:
Quebec Heart Institute/Laval Hospital, Laval University, Sainte-Foy, Quebec, Canada.
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MeSH Terms
Descriptor/Qualifier:
Adult
Aged
Analysis of Variance
Aortic Valve / physiopathology*
Aortic Valve Stenosis / physiopathology*,  surgery,  ultrasonography
Blood Flow Velocity / physiology
Echocardiography, Doppler
Female
Heart Valve Prosthesis*
Humans
Male
Middle Aged
Models, Cardiovascular
Models, Structural
Pulsatile Flow / physiology
Stroke Volume / physiology
Vascular Resistance / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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