title: Physiology and analysis of the electrocardiographic T wave in mice.
abstract: OBJECTIVE
  The murine electrocardiogram (ECG) is a valuable tool in cardiac research, although the definition of the T wave has been a matter of debate for several years potentially leading to incomparable data. By this study, we seek to make a clear definition of the murine T wave. Moreover, we investigate the consequences of performing QT interval correction in anaesthetized mice.
  
  
  METHODS
  Electrocardiograms from conscious mice were recorded by implanted telemetry devices. Surface ECGs were recorded from anaesthetized mice before and during pharmacological interventions, ventricular ischaemia and heart failure. Right atrial pacing was performed to evaluate the relationship between heart rate and QT intervals.
  
  
  RESULTS
  Electrocardiogram traces of conscious and anaesthetized mice (lead II) showed separable positive J waves and negative T waves. The end of the T wave was determined as the point where the T wave returned to the isoelectric line. Atrial pacing revealed that the duration of the QT interval is independent of heart rate in anaesthetized mice. The calcium channel blocker, verapamil, prolonged the PR interval; however, the polarities of the J and T waves were not changed. Local cardiac ischaemia and β-adrenergic stimulation caused indistinguishable positive J and T waves. In contrast, chronic heart failure caused entirely negative J and T waves. In every case, the end of the T wave was clearly distinguishable on the ECG.
  
  
  CONCLUSIONS
  The end of the T wave is readily available from conscious and anaesthetized mice. Heart rate correction of QT interval duration in the anaesthetized mouse is not recommended.
authors.affiliation: Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark.
authors.forename: T
authors.initials: T
authors.lastname: Speerschneider
authors.forename: M B
authors.initials: MB
authors.lastname: Thomsen
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002908:Chronic Disease; D004195:Disease Models, Animal; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017202:Myocardial Ischemia / Q000503:physiopathology*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D002121:Calcium Channel Blockers; D014700:Verapamil; D007545:Isoproterenol
keywords: J wave; QT correction; T wave; electrocardiogram; telemetry