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Home / Equine Research Bank / Equine Vet J / Exercise-associated rhythm disturbances in poorly performing...
Equine veterinary journal2020; 53(4); 656-669; doi: 10.1111/evj.13354

Exercise-associated rhythm disturbances in poorly performing Thoroughbreds: risk factors and association with racing performance.

Abstract: Exercise-associated cardiac rhythm disturbances are common, but there is a lack of evidence-based criteria on which to distinguish clinically relevant rhythm disturbances from those that are not. Objective: To describe and characterise rhythm disturbances during clinical exercise testing; to explore potential risk factors for these rhythm disturbances and to determine whether they influenced future racing. Methods: Retrospective cohort using a convenience sample. Methods: Medical records were reviewed from two clinical services to identify horses with poor performance and/or respiratory noise with both exercise endoscopy and electrocardiography results. Respiratory and ECG findings recorded by the attending clinicians were described, and for polymorphic ventricular rhythms (n = 12), a consensus team agreed the final rhythm characterisation. Several statistical models analysing risk factors were built and racing records were reviewed to compare horses with and without rhythm disturbance. Results: Of 245 racehorses, 87 (35.5%) had no ectopic/re-entrant rhythms, 110 (44.9%) had isolated premature depolarisations during sinus rhythm and 48 (19.6%) horses had complex tachydysrrythmias. Rhythm disturbances were detected during warm-up in 20 horses (8.2%); during gallop in 61 horses (24.9%) and during recovery in 124 horses (50.6%). Most complex rhythm events occurred during recovery, but there was one horse with a single couplet during gallop and another with a triplet during gallop. Fifteen horses (one with frequent isolated premature depolarisations and 14 complex rhythms) were considered by clinicians to be potentially contributing to poor performance. Treadmill exercise tests, the presence of exercise-associated upper respiratory tract obstructions and National Hunt racehorses were associated with rhythm disturbances. The proportion of horses racing again after diagnosis (82%) was similar in all groups and univariable analysis revealed no significant associations between subsequent racing and the presence of any ectopic/re-entrant rhythm, or the various sub-groups based on phase of exercise in which this was detected. Conclusions: Reliance on retrospective data collection from medical records with no control group. Exercise ECGs were collected using only 1 or 2 leads. Variables examined as risk factors could be considered to be inter-related and our sub-groups were small. Conclusions: This study confirms a high prevalence of cardiac rhythm disturbances, including complex ectopic/re-entrant rhythms, in poorly performing racehorses. Detection of rhythm disturbances may vary with exercise test conditions and exercise-associated upper respiratory tract obstructions increase the risk of rhythm disturbances.
© 2020 EVJ Ltd.
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Publication Date: 2020-10-29 PubMed ID: 32979227DOI: 10.1111/evj.13354Google Scholar: Lookup
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Summary

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The research article investigates the prevalence and potential risk factors of exercise-associated cardiac rhythm disturbances in poorly performing Thoroughbred racehorses and their effects on racing performance.

Objective and Methodology

  • The purpose of this research was to identify and characterize cardiac rhythm disturbances among Thoroughbred horses, understand potential risk factors, and determine how these might affect future performance in races.
  • The study was a retrospective cohort, using data collected from the medical records of two clinical services. The researchers focused on horses with poor performance and/or respiratory noise that had undergone both exercise endoscopy and electrocardiography.
  • The respiratory and ECG findings were analyzed and a consensus team agreed on the final rhythm characterization for polymorphic ventricular rhythms in 12 of these horses.
  • The study implemented several statistical models to study risk factors and reviewed the racing records of the horses to compare those with rhythm disturbances and those without.

Results

  • Out of 245 racehorses studied, 87 had no abnormal rhythms, 110 had premature depolarizations during normal rhythm, and 48 had complex tachyarrhythmias, or abnormal fast heart rhythms.
  • Rhythm disturbances were detected at different phases of exercise: 8.2% during warm-up, 24.9% during gallop, and 50.6% during recovery. Most complex rhythm events occurred during recovery.
  • 15 horses were considered by clinicians to have performance issues potentially attributable to rhythm disturbances.
  • Factors such as treadmill exercise tests, exercise-associated upper respiratory tract obstructions, and being a National Hunt racehorse were found to be associated with rhythm disturbances.
  • The proportion of horses racing again after diagnosis was similar across all groups, and the analysis revealed no significant associations between subsequent racing and the rhythm disturbances or the various sub-groups based on the phase of exercise in which they were detected.

Conclusion

  • The researchers acknowledge the limitations of the study, including reliance on retrospective data collection, collection of exercise ECGs using only one or two leads, interrelation of the examined risk factor variables, and small sub-groups.
  • The study confirms a high prevalence of cardiac rhythm disturbances, including complex ectopic or re-entrant rhythms, in poorly performing racehorses.
  • The detection of rhythm disturbances may vary with exercise test conditions, and exercise-associated upper respiratory tract obstructions increase the risk of rhythm disturbances.

Cite This Article

APA
Marr CM, Franklin S, Garrod G, Wylie C, Smith L, Dukes-McEwan J, Bright J, Allen K. (2020). Exercise-associated rhythm disturbances in poorly performing Thoroughbreds: risk factors and association with racing performance. Equine Vet J, 53(4), 656-669. https://doi.org/10.1111/evj.13354

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 53
Issue: 4
Pages: 656-669

Researcher Affiliations

Marr, Celia M
  • Rossdales Diagnostic Centre, Newmarket, UK.
Franklin, Samantha
  • Equine Sports Medicine Centre, Bristol Vet School, University of Bristol, Bristol, UK.
  • Equine Health and Performance Centre, University of Adelaide, South Australia, SA, Australia.
Garrod, Georgie
  • Rossdales Diagnostic Centre, Newmarket, UK.
Wylie, Claire
  • Rossdales Diagnostic Centre, Newmarket, UK.
Smith, Lewis
  • Rossdales Diagnostic Centre, Newmarket, UK.
Dukes-McEwan, Jo
  • Department of Small Animal Clinical Science (Cardiology Service), Institute of Veterinary Science, Leahurst Campus, University of Liverpool, Neston, Cheshire, UK.
Bright, Jan
  • Colorado State University Veterinary Teaching Hospital, Fort Collins, CO, USA.
Allen, Kate
  • Equine Sports Medicine Centre, Bristol Vet School, University of Bristol, Bristol, UK.

MeSH Terms

  • Animals
  • Arrhythmias, Cardiac / veterinary
  • Electrocardiography
  • Horse Diseases / diagnosis
  • Horse Diseases / epidemiology
  • Horse Diseases / etiology
  • Horses
  • Physical Conditioning, Animal
  • Retrospective Studies
  • Risk Factors

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Citations

This article has been cited 4 times.
  1. Kenchaiwong W, Sangpo P, Kusol A, Pontaema T, Lerdweeraphon W. The position of ground electrode affects electrocardiographic parameters in horses.. Vet World 2022 Apr;15(4):1107-1112.
    doi: 10.14202/vetworld.2022.1107-1112pubmed: 35698497google scholar: lookup
  2. Nath L, Stent A, Elliott A, La Gerche A, Franklin S. Risk Factors for Exercise-Associated Sudden Cardiac Death in Thoroughbred Racehorses.. Animals (Basel) 2022 May 18;12(10).
    doi: 10.3390/ani12101297pubmed: 35625143google scholar: lookup
  3. Ter Woort F, Dubois G, Tansley G, Didier M, Verdegaal L, Franklin S, Van Erck-Westergren E. Validation of an equine fitness tracker: ECG quality and arrhythmia detection.. Equine Vet J 2022 Feb 9;55(2):336-43.
    doi: 10.1111/evj.13565pubmed: 35138653google scholar: lookup
  4. Alberti E, Stucchi L, Lo Feudo CM, Stancari G, Conturba B, Ferrucci F, Zucca E. Evaluation of Cardiac Arrhythmias before, during, and after Treadmill Exercise Testing in Poorly Performing Standardbred Racehorses.. Animals (Basel) 2021 Aug 16;11(8).
    doi: 10.3390/ani11082413pubmed: 34438870google scholar: lookup
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