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Equine veterinary journal2012; 45(3); 309-314; doi: 10.1111/j.2042-3306.2012.00653.x

Ventricular response during lungeing exercise in horses with lone atrial fibrillation.

Abstract: Atrial fibrillation (AF) is the most important dysrhythmia affecting performance in horses and has been associated with incoordination, collapse and sudden death. Limited information is available on ventricular response during exercise in horses with lone AF. Objective: To investigate ventricular response in horses with lone AF during a standardised lungeing exercise test. Methods: A modified base-apex electrocardiogram was recorded at rest and during a standardised lungeing exercise test from 43 horses diagnosed with lone AF. During the test horses walked for 7 min, trotted for 10 min, cantered for 4 min, galloped for 1 min and recovered for 7 min. Results: Individual average heart rate during walk ranged from 42 to 175 beats/min, during trot from 89 to 207 beats/min, during canter from 141 to 269 beats/min, and during gallop from 191 to 311 beats/min. Individual beat-to-beat maximal heart rate ranged from 248 to 492 beats/min. Ventricular premature depolarisations were present in 81% of the horses: at rest (16%), during exercise (69%), and during recovery (2%). In 33% of the horses, broad QRS complexes with R-on-T morphology were found. Conclusions: Exercising horses with lone AF frequently develop disproportionate tachycardia. In addition, QRS broadening and even R-on-T morphology is frequently found. QRS broadening may originate from ventricular ectopic foci or from aberrant intraventricular conduction, for example due to bundle branch block. This might explain the high number of complexes currently classified as ventricular premature depolarisations. Conclusions: Prevalence of QRS broadening and especially R-on-T was very high in horses with AF and was found at low levels of exercise. These dysrhythmias are considered risk factors for the development of ventricular tachycardia and fibrillation and they might explain signs of weakness, collapse or sudden death that have been reported in horses with AF.
© 2012 EVJ Ltd.
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Publication Date: 2012-10-23 PubMed ID: 23094848DOI: 10.1111/j.2042-3306.2012.00653.xGoogle Scholar: Lookup
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  • Journal Article
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  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research examined ventricular responses in horses during lungeing exercise, particularly those with lone atrial fibrillation (AF). The results showed that these horses often develop disproportionate tachycardia, along with QRS broadening and even R-on-T morphology, all of which can pose a significant risk for the development of ventricular tachycardia and fibrillation.

Objective of the Research

  • The primary aim of the study was to investigate how the ventricles respond during a standardised lungeing exercise test in horses with lone atrial fibrillation (AF). This research was vital since AF is the most critical dysrhythmia that impacts horses’ performance and could lead to severe consequences such as sudden death.

Research Methodology

  • The research involved recording a modified base-apex electrocardiogram at rest and during a standardised lungeing exercise test from 43 horses diagnosed with lone AF.
  • The test included different stages: walk for 7 minutes, trot for 10 minutes, canter for 4 minutes, gallop for 1 minute, and recovery for 7 minutes.

Research Findings

  • Horses’ heart rates varied at different stages of the test; walking ranged from 42 to 175 beats/min, trotting from 89 to 207 beats/min, cantering from 141 to 269 beats/min, and galloping from 191 to 311 beats/min. The beat-to-beat maximal heart rate ranged from 248 to 492 beats/min.
  • Ventricular premature depolarisations, an abnormal heartbeat, were found in 81% of horses, with various occurrences at rest (16%), during exercise (69%), and during recovery (2%).
  • 33% of the animals showed broad QRS complexes with R-on-T morphology, an abnormal heart rhythm that can be a precursory sign of cardiac arrest.

Conclusions

  • The exercise triggered a disproportionate heart rate increase, known as tachycardia, in horses with lone AF. Further, many horses showed QRS broadening and R-on-T morphology, which can originate from ventricular ectopic foci or aberrant intraventricular conduction, which might be due to a bundle branch block.
  • Significantly, both QRS broadening and R-on-T were prevalent in horses with AF, even at low exercise levels. These abnormal heart rhythms are potential risk factors for developing ventricular tachycardia and fibrillation. They might explain the signs of weakness, collapse, or sudden death reported in horses with AF.

Cite This Article

APA
Verheyen T, Decloedt A, van der Vekens N, Sys S, De Clercq D, van Loon G. (2012). Ventricular response during lungeing exercise in horses with lone atrial fibrillation. Equine Vet J, 45(3), 309-314. https://doi.org/10.1111/j.2042-3306.2012.00653.x

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 45
Issue: 3
Pages: 309-314

Researcher Affiliations

Verheyen, T
  • Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. tinne.verheyen@ugent.be
Decloedt, A
    van der Vekens, N
      Sys, S
        De Clercq, D
          van Loon, G

            MeSH Terms

            • Animals
            • Atrial Fibrillation / physiopathology
            • Atrial Fibrillation / veterinary
            • Electrocardiography / instrumentation
            • Electrocardiography / methods
            • Electrocardiography / veterinary
            • Female
            • Heart Rate
            • Horse Diseases / diagnosis
            • Horse Diseases / physiopathology
            • Horses
            • Male
            • Physical Conditioning, Animal / methods
            • Ventricular Function / physiology

            Citations

            This article has been cited 17 times.
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            14. Decloedt A, Broux B, De Clercq D, Deprez P, Van Steenkiste G, Vera L, Ven S, van Loon G. Effect of sotalol on heart rate, QT interval, and atrial fibrillation cycle length in horses with atrial fibrillation. J Vet Intern Med 2018 Mar;32(2):815-821.
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