title: Characterisation of regional myocardial dynamics during mechanical alternans in heart of anaesthetised pig.
abstract: OBJECTIVE
  The aim was to investigate the behaviour of regional myocardium during mechanical alternans in a multidirectional manner.
  
  
  METHODS
  Mechanical alternans was induced in 12 anaesthetised open chested pigs by rapid atrial pacing. In contrast to previous studies, regional mechanical activity was simultaneously assessed at up to three different sites on the left ventricle using epicardial measuring devices able to provide multidirectional information on segment motion. Pressure-length loops were plotted to assess different patterns of segmental motion. The integral of pressure and length was calculated to obtain a regional work index for each beat.
  
  
  RESULTS
  Pressure-length loops revealed profound abnormalities in segment motion and work index during regional mechanical alternans. Myocardial segments either performed alternate amounts of positive work on each beat or alternate amounts of positive and negative work on each beat. Alternating segments contracted out of phase with each other and were occasionally stretched during systole.
  
  
  CONCLUSIONS
  The spatio-temporal heterogeneity of regional mechanical behaviour is greatly increased during mechanical alternans.
authors.affiliation: Department of Physiology, Charing Cross and Westminster Medical School, London, United Kingdom.
authors.forename: C F
authors.initials: CF
authors.lastname: Murphy
authors.forename: M J
authors.initials: MJ
authors.lastname: Lab
authors.forename: F G
authors.initials: FG
authors.lastname: Harrison
authors.forename: S M
authors.initials: SM
authors.lastname: Horner
authors.forename: D J
authors.initials: DJ
authors.lastname: Dick
authors.forename: M
authors.initials: M
authors.lastname: Moutoussis
mesh_terms: D000768:Anesthesia, General; D000818:Animals; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D006321:Heart / Q000503:physiopathology*; D006331:Heart Diseases / Q000503:physiopathology*; D013552:Swine