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Beat-to-beat change in myocardial performance index related to load
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.ORCID iD: 0000-0002-5325-2688
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2007 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 51, no 5, 545-552 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: This study was designed to assess the relationship of the "myocardial performance index" (MPI) to the beat-by-beat change in pre-load with static or unchanged contractile status.

METHODS: Eight anesthetized juvenile pigs were studied using direct measurement of the left ventricular pressure and volume. Transient inflation of a vena cava balloon catheter produced controlled pre-load alterations. Consecutive beats were analyzed, grouped for first, second, third, etc. during the pre-load alteration, and evaluated for the change in MPI during the same contractile status with a controlled pre-load alteration. Two pharmacologic inotropic interventions were also included to generate several myocardial conditions in each animal.

RESULTS: MPI demonstrated a strong linear relationship to the pre-load and after-load. MPI increased progressively during decreasing end-diastolic volume, mostly related to changes in ejection time. MPI was observed at the same level for three different myocardial function conditions (all eight animals), with a different relationship between MPI and pre-load noted for each observation.

CONCLUSIONS: MPI is strongly load dependent, and can vary widely in value for the same contractile status if the load is varied. The use of this index in critically ill patients should be limited in this respect. Further work is needed to establish the relationship of MPI to load and contractile status.

Place, publisher, year, edition, pages
2007. Vol. 51, no 5, 545-552 p.
Keyword [en]
Animals, Blood Pressure/physiology, Epinephrine/pharmacology, Isoflurane/pharmacology, Myocardial Contraction/*drug effects/physiology, Myocardial Revascularization/methods, Stroke Volume, Swine, Vasoconstrictor Agents/pharmacology
URN: urn:nbn:se:umu:diva-7139DOI: 10.1111/j.1399-6576.2007.01287.xPubMedID: 17430314OAI: diva2:146810
Available from: 2008-01-04 Created: 2008-01-04 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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