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Left ventricular mechanical dyssynchrony is load independent at rest and during endotoxaemia in a porcine model
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
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2009 (English)In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 196, no 4, 375-383 p.Article in journal (Refereed) Published
Abstract [en]

AIM: In diseased or injured states, the left ventricle displays higher degrees of mechanical dyssynchrony. We aimed at assessing mechanical dyssynchrony ranges in health related to variation in load as well as during acute endotoxin-induced ventricular injury.

METHODS: In 16 juvenile anaesthetized pigs, a five-segment conductance catheter was placed in the left ventricle as well as a balloon-tipped catheter in the inferior vena cava. Mechanical dyssynchrony during systole, including dyssynchrony time in per cent during systole and internal flow fraction during systole, were measured at rest and during controlled pre-load reduction sequences, as well as during 3 h of endotoxin infusion (0.25 microg kg(-)1 h(-1)).

RESULTS: Systolic dyssynchrony and internal flow fraction did not change during the course of acute beat-to-beat pre-load alteration. Endotoxin-produced acute pulmonary hypertension by left ventricular dyssynchrony measures was not changed during the early peak of pulmonary hypertension. Endotoxin ventricular injury led to progressive increases in systolic mechanical segmental dyssynchrony (7.9 +/- 1.2-13.0 +/- 1.3%) and ventricular systolic internal flow fraction (7.1 +/- 2.4-16.6 +/- 2.8%), respectively for baseline and then at hour 3. There was no localization of dyssynchrony changes to segment or region in the ventricular long axis during endotoxin infusion.

CONCLUSION: These results suggest that systolic mechanical dyssynchrony measures may be load independent in health and during acute global ventricular injury by endotoxin. More study is needed to validate ranges in health and disease for parameters of mechanical dyssynchrony.

Place, publisher, year, edition, pages
2009. Vol. 196, no 4, 375-383 p.
Keyword [en]
endotoxaemia; swine; ventricular function
URN: urn:nbn:se:umu:diva-31397DOI: 10.1111/j.1748-1716.2009.01962.xPubMedID: 19302073ISBN: 1748-1716 (Electronic)OAI: diva2:292945
A'roch, R Steendijk, P Oldner, A Weitzberg, E Konrad, D Johansson, G Haney, M Research Support, Non-U.S. Gov't England Acta physiologica (Oxford, England) Acta Physiol (Oxf). 2009 Aug;196(4):375-83. Epub 2009 Mar 19.Available from: 2010-02-10 Created: 2010-02-10 Last updated: 2015-09-15Bibliographically approved
In thesis
1. Left ventricular function's relation to load, experimental studies in a porcine model
Open this publication in new window or tab >>Left ventricular function's relation to load, experimental studies in a porcine model
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Loading conditions are recognized to influence ventricular function according to the Starling relationship for length/stretch and force.  Many modern echocardiographic parameters which have been announced as describing ventricular function and contractile status, may be confounded by uncontrolled and unmeasured load.  These studies aimed to measure the relation between four differ­ent types of assessments of ventricular dysfunction and degrees of load.  Study examined the ‘myo­cardial performance index’ (MPI).  Study II examined long axis segmental mechanical dyssynchrony.  Study III examined tissue velocities, and Study IV examined ventricular twist.  All studies aimed to describe the relation of these parameters both to load and to inotropic changes.

Methods:  In anesthetized juvenile pigs, left ventricular (LV) pressure and volume were measured continuously and their relationship (LVPVR) was analysed.  Preload alterations were brought about by inflation of a balloon tipped catheter in the inferior vena cava (IVCBO).  Inotropic interventions were brought about by either an overdose of anesthetic (combine intravenous pentobarbital and inhaled isoflurane, Study I), or beta blocker and calcium channel blocker given in combination (Stud­ies III and IV).  In one study (II), global myocardial injury and dysfunction was induced by endotoxin infusion.  MPI measurements were derived from LVPVR heart cycle intervals for isovolumic contrac­tion and relaxation as well as ejection time.  Long axis segmental dyssynchrony was derived by ana­lyzing for internal flow and time with segmental dyssynchronous segment volume change during systole, hourly before and during 3 hours of endotoxin infusion.  Myocardial tissue velocities were measured during IVCBO at control, during positive and then later negative inotropic interventions.  The same for apical and base circumferential rotational velocities by speckle tracking.  Load markers (including end-diastolic volume) were identified for each beat, and the test parameters were analysed together with load for a relation.  The test parameters were also tested during single apneic beats for a relation to inotropic interventions.

Results: MPI demonstrated a strong and linear relationship to both preload and after-load, and this was due to changes in ejection time, and not the isovolumic intervals.  Long axis segmental dyssyn­chrony increased during each hour of endotoxin infusion and global myocardial injury.  This dysyn­chrony parameter was independent of load when tested by IVCBO. Peak systolic velocities were strongly load-independent, though not in all the inotropic situations and by all measurement axes.  Peak systolic strain was load-dependent, and not strongly related to inotropic conditions.  Peak sys­tolic LV twist and untwist were strongly load-dependent.

Conclusions: MPI is strongly load-dependent, and can vary widely in value for the same contractile status if the load is varied.  Mechanical dyssynchrony measures are load-independen in health and also in early global endotoxin myocardial injury and dysfunction.  Peak sytole velocities are a clinically robust parameter of LV regional and global performance under changing load, though peak systolic strain seems to be load-dependent.  Left ventricular twist and untwist are load-dependent in this pig model.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2011. 67 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1425
heart function, preload, afterload, contractility, myocardial tissue velocity, speckle tracking
National Category
Anesthesiology and Intensive Care
Research subject
urn:nbn:se:umu:diva-43605 (URN)978-91-7459-225-2 (ISBN)
Public defence
2011-05-27, Sal B, 9 tr, Tandläkarhögskolan, Norrlands Universitetssjukhus, Umeå, 13:00 (English)
Available from: 2011-05-06 Created: 2011-05-04 Last updated: 2011-05-09Bibliographically approved

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