title: Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.
abstract: BACKGROUND
  Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited.
  
  
  OBJECTIVE
  To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions.
  
  
  METHODS
  Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket.
  
  
  METHODS
  Forty-nine horses treated with quinidine were identified (29 Warmbloods, 20 Thorougbreds, 1 Anglo-Arabian). Details of signalment, history, duration physical examination and echocardiography including left atrial size and presence of mitral regurgitation were retrieved. Clinical details including mean weight, age and left atrial size were compared between clinics using independent samples t test. Association between variables and cardioconversion were evaluated in a backwards logistic regression using Akaike's information criterium (AIC) and odds ratios were calculated. Factors were sex, clinic, breed, mitral regurgitation, duration and poor performance. Covariates were age, weight and the size of the left atrium. Significance was set at 0.05.
  
  
  RESULTS
  Fifty-one horses (mean age 8.8 s.d. 4.5 years) were treated with quinidine sulfate, 18 also received digoxin. Eighty per cent converted to sinus rhythm. In 8 horses the known duration was less than 3 months. The only factor associated with successful treatment was the use of digoxin in combination with quinidine sulfate (odds ratio 12.4; 95% CI 2.61 and 91.85 according to AIC analysis).
  
  
  CONCLUSIONS
  In this retrospective case series, there is much potential for bias in the data; however, the use of digoxin in addition to quinidine was associated with improved conversion rates regardless of breed even though AF duration was unknown in most horses. Ethical animal research: Research ethics committee oversight not currently required by this conference: retrospective study of clinical records. Explicit owner informed consent for inclusion of animals in this study was not stated.
  
  
  BACKGROUND
  None. Competing interests: None declared.
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
authors.forename: R J
authors.initials: RJ
authors.lastname: Lotstra
authors.affiliation: Department of Farm Animal Health, Dept. Epidemiology, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van den Broek
authors.affiliation: Royal Veterinary College, Hawkshead Lane, North Mymms, Hertfordshire, AL7 9TA, UK.
authors.forename: T
authors.initials: T
authors.lastname: Power
authors.affiliation: Rossdales Equine Hospital and Diagnostic Centre, Cotton End Road, Exning, Newmarket, CB8 7NN, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Marr
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
authors.forename: I D
authors.initials: ID
authors.lastname: Wijnberg