title: Atrial Premature Depolarization-Induced Changes in QRS and T Wave Morphology on Resting Electrocardiograms in Horses.
abstract: BACKGROUND
  The electrocardiographic differentiation between atrial (APDs) and ventricular (VPDs) premature depolarizations is important. P wave prematurity and normal QRS and T wave morphology generally are used as discriminating criteria for APDs.
  
  
  OBJECTIVE
  The aim of this study was to determine whether P, Q, R, S, and T wave amplitude, PQ interval, QRS and P wave duration and P and T wave morphology differ between APDs and sinus beats. To determine the relationship between the RR coupling interval and the change in S wave amplitude between sinus beats and APDs.
  
  
  METHODS
  Case-control study. From a modified base-apex configuration of 30 horses with APDs at rest, sinus beat and APD associated preceding RR interval, P, PQ and QRS duration and P, R, S, and T wave amplitudes were measured. Linear mixed models and logistic regression were used to determine the effect of APDs on the ECG variables studied.
  
  
  RESULTS
  In comparison to sinus beats, APDs were associated with a significant (P < .001) change in P amplitude (-0.03 ± 0.01 mV) and increase in S (0.20 ± 0.02 mV) and T (0.08 ± 0.03 mV) amplitude. PQ (-20.3 ± 5.2 ms) and RR (-519 ± 14 ms) interval and P duration (-21.1 ± 3.0 ms) decreased (P < .001). APDs were significantly associated with a singular positive P wave (OR: 11.0, P < .001) and were more likely to have a monophasic positive T wave (OR: 9.2, P < .001). A smaller RR coupling interval was associated with an increased relative difference in S amplitude (P < .01).
  
  
  CONCLUSIONS
  Atrial premature depolarizations may lead to changes in QRS and T wave morphology. Knowledge of these changes is important to avoid interpreting certain APDs as VPDs.
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Broux
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: De Clercq
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Decloedt
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Van Der Vekens
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: T
authors.initials: T
authors.lastname: Verheyen
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Ven
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Pardon
authors.affiliation: Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: van Loon
mesh_terms: D000818:Animals; D018880:Atrial Premature Complexes / Q000175:diagnosis*; D016022:Case-Control Studies; D004562:Electrocardiography / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D008297:Male
keywords: Cardiology; Electrocardiography; Equine