title: Electrocardiographic characteristics of endurance-trained Alaskan sled dogs.
abstract: OBJECTIVE
  To determine electrocardiographic characteristics of endurance-trained Alaskan sled dogs.
  
  
  METHODS
  Case series.
  
  
  METHODS
  319 Alaskan sled dogs entered to compete in the 1994 Iditarod Trail Sled Dog Race.
  
  
  METHODS
  ECG were recorded while dogs were standing and were analyzed digitally.
  
  
  RESULTS
  Amplitudes of P waves (median, 0.40 mV; fifth to 95th percentile range, 0.11 to 0.61 mV) and R waves in lead II (median, 3.02 mV; fifth to 95th percentile range, 1.49 to 4.40 mV) were high; durations of P waves in lead II (median, 61 milliseconds; fifth to 95th percentile range, 36 to 96 milliseconds), QRS complexes (median, 64 milliseconds; fifth to 95th percentile range, 52 to 80 milliseconds), and QT intervals (median, 236 milliseconds; fifth to 95th percentile range, 208 to 277 milliseconds) were prolonged. Median value for mean axis of ventricular depolarization was 57 degrees (fifth to 95th percentile range, 19 to 90 degrees). Atrial and ventricular premature depolarizations were observed in 3 (0.9%) and 4 (1.3%) of 319 dogs, respectively, and paroxysmal ventricular tachycardia was detected in 1 (0.3%).
  
  
  CONCLUSIONS
  Results suggest that electrocardiographic characteristics of endurance-trained Alaskan sled dogs differ from those reported for nonsled dogs, probably as a result of effects of endurance training on heart size. Some of these characteristics could be mistaken as evidence of pathologic cardiac hypertrophy.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University, Columbus 43210, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Hinchcliff
authors.forename: P D
authors.initials: PD
authors.lastname: Constable
authors.forename: J W
authors.initials: JW
authors.lastname: Farris
authors.forename: K E
authors.initials: KE
authors.lastname: Schmidt
authors.forename: R L
authors.initials: RL
authors.lastname: Hamlin
mesh_terms: D000413:Alaska; D000818:Animals; D004285:Dogs / Q000502:physiology*; D004562:Electrocardiography / Q000662:veterinary*; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012016:Reference Values