Cardiac electrophysiological adaptations in the equine athlete—Restitution analysis of electrocardiographic features

Li, Mengye, Chadda, Karan R., Matthews, Gareth D.K. ORCID:, Marr, Celia M., Huang, Christopher L.H. and Jeevaratnam, Kamalan (2018) Cardiac electrophysiological adaptations in the equine athlete—Restitution analysis of electrocardiographic features. PLoS One, 13 (3). ISSN 1932-6203

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Exercising horses uniquely accommodate 7–8-fold increases in heart rate (HR). The present experiments for the first time analysed the related adaptations in action potential (AP) restitution properties recorded by in vivo telemetric electrocardiography from Thoroughbred horses. The horses were subjected to a period of acceleration from walk to canter. The QRS durations, and QT and TQ intervals yielded AP conduction velocities, AP durations (APDs) and diastolic intervals respectively. From these, indices of active, λ = QT/(QRS duration), and resting, λ0 = TQ/(QRS duration), AP wavelengths were calculated. Critical values of QT and TQ intervals, and of λ and λ0 at which plots of these respective pairs of functions showed unity slope, were obtained. These were reduced by 38.9±2.7% and 86.2±1.8%, and 34.1±3.3% and 85.9±1.2%, relative to their resting values respectively. The changes in λ were attributable to falls in QT interval rather than QRS duration. These findings both suggested large differences between the corresponding critical (129.1±10.8 or 117.4±5.6 bpm respectively) and baseline HRs (32.9±2.1 (n = 7) bpm). These restitution analyses thus separately identified concordant parameters whose adaptations ensure the wide range of HRs over which electrophysiological activation takes place in an absence of heart block or arrhythmias in equine hearts. Since the horse is amenable to this in vivo electrophysiological analysis and displays a unique wide range of heart rates, it could be a novel cardiac electrophysiology animal model for the study of sudden cardiac death in human athletes.

Item Type: Article
Additional Information: Funding Information: KRC was funded by the Physiological Society ( at the University of Surrey. GDKM was funded by the Wellcome Trust and CLHH is funded by the Medical Research Council (MR/M001288/1) (, Wellcome Trust (105727/Z/14/Z) ( and British Heart Foundation (PG/14/79/31102) ( Department of Preclinical Veterinary Sciences, School of Veterinary Medicine, University of Surrey, provided travel and subsistence funding for KJ to undertake the experiments. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Publisher Copyright: © 2018 Li et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Uncontrolled Keywords: biochemistry, genetics and molecular biology(all),agricultural and biological sciences(all),general ,/dk/atira/pure/subjectarea/asjc/1300
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
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Depositing User: LivePure Connector
Date Deposited: 10 Nov 2022 13:30
Last Modified: 10 Nov 2022 13:30
DOI: 10.1371/journal.pone.0194008

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