title: State diagrams of the heart--a new approach to describing cardiac mechanics.
abstract: BACKGROUND
  Cardiac time intervals have been described as a measure of cardiac performance, where prolongation, shortening and delay of the different time intervals have been evaluated as markers of cardiac dysfunction. A relatively recently developed method with improved ability to measure cardiac events is Tissue Doppler Imaging (TDI), allowing accurate measurement of myocardial movements.
  
  
  METHODS
  We propose the state diagram of the heart as a new visualization tool for cardiac time intervals, presenting comparative, normalized data of systolic and diastolic performance, providing a more complete overview of cardiac function. This study aimed to test the feasibility of the state diagram method by presenting examples demonstrating its potential use in the clinical setting and by performing a clinical study, which included a comparison of the state diagram method with established echocardiography methods (E/E' ratio, LVEF and WMSI). The population in the clinical study consisted of seven patients with non ST-elevation myocardial infarction (NSTEMI) and seven control subjects, individually matched according to age and gender. The state diagram of the heart was generated from TDI curves from seven positions in the myocardium, visualizing the inter- and intraventricular function of the heart by displaying the cardiac phases.
  
  
  RESULTS
  The clinical examples demonstrated that the state diagram allows for an intuitive visualization of pathological patterns as ischemia and dyssynchrony. Further, significant differences in percentage duration between the control group and the NSTEMI group were found in eight of the totally twenty phases (10 phases for each ventricle), e.g. in the transition phases (Pre-Ejection and Post-Ejection). These phases were significantly longer (> 2.18%) for the NSTEMI group than for the control group (p < 0.05). No significant differences between the groups were found for the established echocardiography methods.
  
  
  CONCLUSIONS
  The test results clearly indicate that the state diagram has potential to be an efficient tool for visualization of cardiac dysfunction and for detection of NSTEMI.
authors.affiliation: School for Technology and Health, Royal Institute of Technology, Alfred Nobels Allé 10, SE-14152 Huddinge, Sweden. matilda.larsson@sth.kth.se
authors.forename: Matilda
authors.initials: M
authors.lastname: Larsson
authors.forename: Anna
authors.initials: A
authors.lastname: Bjällmark
authors.forename: Jonas
authors.initials: J
authors.lastname: Johnson
authors.forename: Reidar
authors.initials: R
authors.lastname: Winter
authors.forename: Lars-Ake
authors.initials: LA
authors.lastname: Brodin
authors.forename: Stig
authors.initials: S
authors.lastname: Lundbäck
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D003196:Computer Graphics; D004452:Echocardiography / Q000379:methods*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006331:Heart Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D014584:User-Computer Interface