title: Occurrence of cardiac arrhythmias in Standardbred racehorses.
abstract: BACKGROUND
  Cardiac arrhythmias are a recognised but poorly characterised problem in the Standardbred racehorse. Frequency data could aid the development of cardiac arrhythmia screening programmes.
  
  
  OBJECTIVE
  To characterise the occurrence of cardiac arrhythmias in Standardbreds prior to racing and in the late post race period using a handheld, noncontinuous recording device.
  
  
  METHODS
  Prospective, observational study, convenience sampling.
  
  
  METHODS
  Noncontinuous electrocardiographic recordings were obtained over a 12 week period from Standardbred horses competing at a single racetrack. Electrocardiograms were obtained before racing and between 6 and 29 min after the race using a handheld recording device. Prevalence of arrhythmias was calculated for all horses and overall frequency of arrhythmias was calculated for race starts and poor performers. Univariate logistic regression analysis was used to identify risk factors for cardiac arrhythmias.
  
  
  RESULTS
  A total of 8657 electrocardiogram recordings were obtained from 1816 horses. Six horses had atrial fibrillation after racing (prevalence = 0.11%, frequency = 0.14%), one horse had supraventricular tachycardia before racing (prevalence = 0.06%, frequency = 0.02%), and 2 horses had ventricular tachyarrhythmias after racing (prevalence = 0.06%, frequency = 0.05%). The frequency of atrial fibrillation among race starts with poor performance was 1.3-2.0%. Increasing age was a significant risk factor for the presence of atrial premature contractions before racing and atrial fibrillation and ventricular ectopy after racing.
  
  
  CONCLUSIONS
  Both physiological and pathological cardiac arrhythmias can be detected in apparently healthy Standardbred horses in the prerace and late post race period using noncontinuous recording methods. Future studies should examine cumulative training or racing hours as a risk factor for cardiac arrhythmia. The prevalence and frequency information may be useful for track veterinarians and regulatory personnel following trends in cardiac arrhythmias.
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, USA.
authors.forename: J
authors.initials: J
authors.lastname: Slack
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Boston
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, USA.
authors.forename: L R
authors.initials: LR
authors.lastname: Soma
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, USA.
authors.forename: V B
authors.initials: VB
authors.lastname: Reef
mesh_terms: D000375:Aging; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000662:veterinary*; D004562:Electrocardiography / Q000662:veterinary; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D013177:Sports; D013696:Temperature
keywords: Standardbred; atrial fibrillation; horse; poor performance; ventricular arrhythmias