title: Assessment of 3D motion increases the applicability of accelerometers for monitoring left ventricular function.
abstract: OBJECTIVE
  Miniaturized accelerometers attached to the epicardium have been shown to provide useful clinical information. However, attachment of such a sensor has been cumbersome due to requirement of aligning the three sensor axes with the cardiac coordinate axes, limiting clinical utility. We propose a new method to process the three-dimensional (3D) accelerometer signal that does not require such alignment.
  
  
  METHODS
  In 20 open-chest pigs, miniaturized 3D accelerometers were fixated on the epicardium in apical and basal regions of left ventricle. Accelerations in circumferential, longitudinal and radial directions were measured and a 3D velocity vector was calculated. Systolic velocity along the 3D vector and velocities in circumferential, longitudinal and radial directions were compared with the positive time derivate of left ventricular pressure during changes in global left ventricular function (epinephrine, esmolol and fluid loading) and to strain echocardiography during left anterior descending artery occlusion.
  
  
  RESULTS
  Distinct changes in all accelerometer velocities were observed during alterations on global and regional left ventricular function. Accelerometer 3D and circumferential systolic velocities in apical region best reflected left ventricular function during interventions on global function by correlating significantly with the positive time derivate of left ventricular pressure, r = 0.83 and r = 0.86, respectively. The accelerometer 3D velocity also demonstrated equally good capacity as circumferential velocity in discriminating coronary occlusion from interventions on global left ventricular function with sensitivity/specificity of 0.90/0.83 and 0.90/0.86, respectively.
  
  
  CONCLUSIONS
  Accelerometer 3D systolic velocity showed very good correspondence to changes in global and regional left ventricular function. Our results demonstrate that by the use of the accelerometer 3D motion vector, no alignment of the sensor with the cardiac coordinate axes was required. This increases potential clinical applicability of the accelerometer in cardiac surgery.
authors.affiliation: The Intervention Centre, Oslo University Hospital, Oslo, Norway Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway olegry@ous-hf.no.
authors.forename: Ole-Johannes H N
authors.initials: OJ
authors.lastname: Grymyr
authors.affiliation: The Intervention Centre, Oslo University Hospital, Oslo, Norway Department of Cardiology, Oslo University Hospital, Oslo, Norway.
authors.forename: Espen W
authors.initials: EW
authors.lastname: Remme
authors.affiliation: The Intervention Centre, Oslo University Hospital, Oslo, Norway Department of Anaesthesiology, Oslo University Hospital, Oslo, Norway.
authors.forename: Andreas
authors.initials: A
authors.lastname: Espinoza
authors.affiliation: Department of Cardiology, Oslo University Hospital, Oslo, Norway.
authors.forename: Helge
authors.initials: H
authors.lastname: Skulstad
authors.affiliation: The Intervention Centre, Oslo University Hospital, Oslo, Norway Department of Informatics, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway.
authors.forename: Ole J
authors.initials: OJ
authors.lastname: Elle
authors.affiliation: The Intervention Centre, Oslo University Hospital, Oslo, Norway Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.
authors.forename: Erik
authors.initials: E
authors.lastname: Fosse
authors.affiliation: The Intervention Centre, Oslo University Hospital, Oslo, Norway.
authors.forename: Per S
authors.initials: PS
authors.lastname: Halvorsen
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D000818:Animals; D004562:Electrocardiography; D004867:Equipment Design; D005260:Female; D021621:Imaging, Three-Dimensional; D008297:Male; D008904:Miniaturization; D008991:Monitoring, Physiologic / Q000379:methods*; D015203:Reproducibility of Results; D013552:Swine; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: Cardiac monitoring; Left ventricular function; Motion sensor