title: Determination of left ventricular long-axis orientation using MRI: changes during the respiratory and cardiac cycles in normal and diseased subjects.
abstract: BACKGROUND
  It has previously been shown that magnetic resonance imaging (MRI) can be used to accurately determine left ventricular (LV) long-axis orientation in healthy individuals. However, the inter- and intra-observer variability in patients with acute coronary syndrome (ACS) and chronic heart failure (CHF) has not been explored. Furthermore, the changes in LV long-axis orientation because of respiration and during the cardiac cycle remain to be determined.
  
  
  METHODS
  LV long-axis orientation was determined by MRI in the frontal and transverse planes in 44 subjects with no cardiac disease, 20 ACS patients and 13 CHF patients. Changes in LV long-axis orientation because of respiration were assessed in a subset of 25 subjects. Changes during the cardiac cycle were assessed in six subjects from each subject group. Reproducibility was assessed by a re-examination of 17 subjects after 28 days.
  
  
  RESULTS
  The inter- and intra-observer variability for LV long-axis orientation was low for all subject groups. The difference between the baseline and the 28 days examinations was -1.4+/-5.9 degrees and -0.8+/-4.4 degrees in the frontal and transverse planes, respectively. No significant change in LV long-axis orientation was found between end-expiration and end-inspiration (frontal plane, P=0.63 and transverse plane, P=0.42; n=25). No significant difference in change of the LV long-axis orientation during the cardiac cycle was found between the subject groups (frontal plane, chi-square 1.8, P=0.40 and transverse plane, chi-square 5.7, P=0.06).
  
  
  CONCLUSIONS
  There is a low inter-and intra-observer variability and a high reproducibility for determining LV long-axis orientation in patients with no cardiac disease as well as in patients with ACS or CHF. There is no significant change in LV long-axis orientation due to respiration, and only small changes during the cardiac cycle in these groups.
authors.affiliation: Glasgow Cardiac Magnetic Resonance Unit, Glasgow, Lanarkshire, UK. j.e.foster@clinmed.gla.ac.uk
authors.forename: John E
authors.initials: JE
authors.lastname: Foster
authors.forename: Henrik
authors.initials: H
authors.lastname: Engblom
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Martin
authors.forename: Galen S
authors.initials: GS
authors.lastname: Wagner
authors.forename: Tracey
authors.initials: T
authors.lastname: Steedman
authors.forename: Stefania
authors.initials: S
authors.lastname: Ferrua
authors.forename: Alex T
authors.initials: AT
authors.lastname: Elliott
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Dargie
authors.forename: Bjoern A
authors.initials: BA
authors.lastname: Groenning
mesh_terms: D000328:Adult; D002908:Chronic Disease; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006321:Heart / Q000502:physiology* / Q000503:physiopathology; D006333:Heart Failure / Q000503:physiopathology*; D006352:Heart Ventricles / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012016:Reference Values; D015203:Reproducibility of Results; D012143:Respiratory Physiological Phenomena; D016277:Ventricular Function, Left / Q000502:physiology*