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Influence of Atrioventricular Interaction on Mitral Valve Closure and Left Ventricular Isovolumic Contraction Measured by Tissue Doppler Imaging.
MedLine Citation:
PMID:  23192849     Owner:  NLM     Status:  Publisher    
BACKGROUND: -The influence of atrioventricular (AV) interaction on mitral valve closure (MVC) and left ventricular (LV) isovolumic contraction is not fully clarified. We investigated the relationship between AV delay, MVC and LV isovolumic contraction using a horse model because of the low heart rate and physiologically long AV delay. METHODS AND RESULTS: -Six horses were evaluated during sinus rhythm (SR), right ventricular pacing without preceding atrial contraction (RVP) and dual-chamber pacing at AV delays of 150-350 ms, programmed at a constant rate. Right parasternal four-chamber views were recorded for simultaneous measurements of MVC from anatomical M-mode and radial tissue Doppler-based LV pre-ejection velocity and isovolumic acceleration (IVA). During SR and long AV delays (≥300 ms), two positive pre-ejection velocity peaks were present. The first peak was identified as LV recoil during atrial relaxation and consistently preceded MVC by 33±17 ms. The second peak was related to LV isovolumic contraction, occurring after MVC. This suggests that MVC was caused by atrial relaxation and followed by true isovolumic contraction. During short AV delays (<300 ms) and RVP, MVC occurred significantly later. Only one pre-ejection peak was present, of which the end coincided with MVC with a mean difference of -1.5±10 ms. This suggests that LV contraction caused MVC. Peak velocity and IVA were significantly higher (P<0.001) as the mitral valve was open at the onset of LV contraction. CONCLUSIONS: -Depending on the AV delay, MVC can be atrio- or ventriculogenic, resulting in significant alterations of the LV peak pre-ejection velocity and IVA.
Annelies Decloedt; Tinne Verheyen; Stanislas Sys; Dominique De Clercq; Bart Bijnens; Gunther van Loon
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-28
Journal Detail:
Title:  Circulation. Cardiovascular imaging     Volume:  -     ISSN:  1942-0080     ISO Abbreviation:  Circ Cardiovasc Imaging     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101479935     Medline TA:  Circ Cardiovasc Imaging     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1 Ghent University, Ghent, Belgium;
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