title: Computer-based analysis of dynamic QT changes: toward high precision and individual rate correction.
abstract: BACKGROUND
  New strategies are needed to improve the results of automatic measurement of the various parts of the ECG signal and their dynamic changes.
  
  
  METHODS
  The EClysis software processes digitally-recorded ECGs from up to 12 leads at 500 Hz, using strictly defined algorithms to detect the PQRSTU points and to measure ECG intervals and amplitudes. Calculations are made on the averaged curve of each sampling period (beat group) or as means +/- SD for beat groups, after being analyzed at the individual beat level in each lead. Resulting data sets can be exported for further statistical analyses. Using QT and R-R measured on beat level, an individual correction for the R-R dependence can be performed.
  
  
  RESULTS
  EClysis assigns PQRSTU points and intervals in a sensitive and highly reproducible manner, with coefficients of variation in ECG intervals corresponding to ca. 2 ms in the simulated ECG. In the normal ECG, the CVs are 2% for QRS, 0.8% for QT, and almost 6% for PQ intervals. EClysis highlights the increase in QT intervals and the decrease of T-wave amplitudes during almokalant infusion versus placebo. Using the observed linear or exponential relationships to adjust QT for R-R dependence in healthy subjects, one can eliminate this dependence almost completely by individualized correction.
  
  
  CONCLUSIONS
  The EClysis system provides a precise and reproducible method to analyze ECGs.
authors.affiliation: Experimental Medicine, AstraZeneca R & D Mölndal, S-431 83 Mölndal, Sweden. Corina.Dota@astrazeneca.com
authors.forename: Corina
authors.initials: C
authors.lastname: Dota
authors.forename: Bo
authors.initials: B
authors.lastname: Skallefell
authors.forename: Nils
authors.initials: N
authors.lastname: Edvardsson
authors.forename: Gunnar
authors.initials: G
authors.lastname: Fager
mesh_terms: D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D015233:Models, Statistical; D008962:Models, Theoretical; D011412:Propanolamines / Q000494:pharmacology; D012016:Reference Values; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012984:Software
chemical_list: D000889:Anti-Arrhythmia Agents; D011412:Propanolamines; C074334:almokalant