The equine electrocardiogram with standardized body and limb positions.
Abstract: Eleven-lead electrocardiograms (ECGs) were recorded from 50 Thoroughbred (TB) and 50 Standard bred (SB) horses at rest with 40 tracings being selected from each group for more complete analysis. Incomplete atrioventricular block with dropped beats commonly reported in mature horses was recorded only in the TB (15%), while wandering of the atrial pacemaker (WAP) thought also to be associated with variations in tone of the autonomic nervous system was detected almost equally in both breeds (30%). In some horses (12.5%), the initial component of the P wave (P1) did not vary as seen with WAP but had a mean manifest electric axis in the frontal plane between 0 and -64 degrees with vectors directed craniad and sinistrad. Breed differences were noted for the mean duration of the P-wave and for the PR and QT intervals while no significant differences were present for mean heart rate. Significant differences have also been reported for other ECG values (amplitude and duration) in relation to age, breed and sex. It may be of value when attempting to determine the clinical or research significance of cardiac vectors or other ECG parameters, to establish values for each of the different breeds. Interpretation of ST-segment deviations and changes in the form of the T-wave are complicated by their associations with conditions of excitement or exercise in clinically normal horses as well as in those with organic heart disease. The diagnostic significance of changes in amplitude and direction of the T-wave requires further elucidation.
Publication Date: 1982-07-01 PubMed ID: 7105763
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- Journal Article
Summary
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The research aimed to investigate differences in electrocardiogram (ECG) readings of Thoroughbred and Standardbred horses under resting conditions. Findings showed variations in atrioventricular block, atrial pacemaker wanderings, P-wave duration, PR and QT intervals, and heart rate. The results suggest the potential value of establishing breed-specific cardiac values for diagnostic and research purposes.
Research Method
- The researchers collected and analyzed 11-lead ECGs from 50 Thoroughbred and 50 Standardbred horses under resting conditions. Out of these, 40 readings from each group were selected for a more detailed analysis.
- The variations in atrioventricular block occurrence and wandering of the atrial pacemaker, both theorized to be related to the autonomic nervous system’s tone, were particularly noticed.
Research Findings
- The Thoroughbred horses showed a 15% rate of incomplete atrioventricular block with dropped beats, which is often reported in mature horses, while Standardbred horses showed no such occurrences.
- The wandering of the atrial pacemaker was evident in around 30% of both Thoroughbred and Standardbred horses.
- In 12.5% of the horses, the first component of the P-wave did not fluctuate, which is generally seen with a wandering atrial pacemaker. However, the mean manifest electric axis in these instances was between 0 and -64 degrees, with vectors pointing towards the horse’s head and left side.
- There were breed-wise variations reported for the average duration of the P-wave, PR and QT intervals.
- However, the mean heart rate showed no significant differences between the two breeds.
Implications
- Breed-related differences were found in significant ECG values, including amplitude and duration, in addition to the horses’ age and sex.
- This highlights the potential benefits of establishing breed-specific cardiac values when trying to interpret the clinical or research relevance of cardiac vectors or other ECG parameters.
- However, the interpretation of ST-segment deviations and changes in the T-wave form are made complex due to potential associations with conditions of excitement or exercise in horses – both clinically normal and those with organic heart diseases.
- The diagnostic significance of changes in the T-wave’s amplitude and direction is still unclear and calls for further study.
Cite This Article
APA
Fregin GF.
(1982).
The equine electrocardiogram with standardized body and limb positions.
Cornell Vet, 72(3), 304-324.
Publication
Researcher Affiliations
MeSH Terms
- Animals
- Arrhythmias, Cardiac / diagnosis
- Arrhythmias, Cardiac / veterinary
- Electrocardiography / veterinary
- Female
- Heart Block / diagnosis
- Heart Block / veterinary
- Horse Diseases / diagnosis
- Horses / physiology
- Male
- Posture
Citations
This article has been cited 4 times.- Triguinho A, Fontes-Sousa AP, Pimenta J, Cotovio M. Electrocardiographic Reference Values in Clinically Healthy Lusitano Horses.. Vet Sci 2023 Aug 10;10(8).
- Hesselkilde EM, Isaksen JL, Petersen BV, Carstensen H, Jespersen T, Pehrson S, Kanters JK, Buhl R. A novel approach for obtaining 12-lead electrocardiograms in horses.. J Vet Intern Med 2021 Jan;35(1):521-531.
- Difruscia R, O'grady M, Hill B. 1. When and why should I do an electrocardiogram?. Can Vet J 1991 Mar;32(3):182-3.
- Amory H, Rollin FA, Genicot BC, Beduin JM, Lekeux PM. Comparative study of the body surface electrocardiogram in double-muscled and conventional calves.. Can J Vet Res 1993 Jul;57(3):139-45.
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