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Signal-averaged electrocardiography in horses: characteristics of ventricular late potentials in healthy Thoroughbreds and horses with cardiac abnormalities.
Abstract: Sudden death in horses, often attributed to lethal arrhythmias, poses significant welfare and economic risks, yet its prediction remains challenging. This study aimed to characterize ventricular micro-potentials using signal-averaged electrocardiography (SAECG) and evaluate their potential for assessing sudden death risk. High-resolution orthogonal X-, Y-, and Z-lead ECGs were recorded in 24 healthy Thoroughbreds (aged 2-31 years), one horse with bupivacaine-induced myocardial injury, and three horses with persistent pathological murmurs. SAECG parameters, including filtered QRS duration (fQRS), LAS40, RMS40, and RMS50, were analyzed from the vector magnitude waveform. In healthy horses, fQRS showed a significant positive correlation with age, with older horses exhibiting a significantly longer fQRS and LAS40 and lower RMS40 and RMS50 compared with younger horses, likely reflecting age-related myocardial fibrosis. The experimental myocardial injury model, characterized by histopathologically confirmed necrosis, resulted in a prolonged fQRS and LAS40 and decreased RMS40 and RMS50, consistent with the development of ventricular late potentials. Conversely, horses with persistent cardiac murmurs showed SAECG parameters within the range of healthy horses, indicating that valvular abnormalities alone do not significantly affect intraventricular conduction. These findings demonstrate that SAECG can effectively detect ventricular micro-potentials and reflect structural myocardial changes such as necrosis and fibrosis in horses. Consequently, SAECG analysis appears to be a promising non-invasive tool for screening the risk of lethal arrhythmias and sudden death in equine clinical practice, especially when combined with other diagnostic modalities.
©2026 The Japanese Society of Equine Science.
Publication Date: 2026-06-13 PubMed ID: 42325406PubMed Central: PMC13276396DOI: 10.1294/jes.2.41Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Overview
- This study used signal-averaged electrocardiography (SAECG) to detect small electrical signals in the hearts of horses, aiming to identify markers that could predict sudden cardiac death.
- By comparing healthy Thoroughbreds, horses with induced heart injury, and horses with heart murmurs, researchers assessed how SAECG parameters relate to heart health and structural changes.
Introduction and Purpose
- Sudden death in horses, often due to dangerous arrhythmias, is a major welfare and economic issue but is hard to predict before it occurs.
- The study aimed to investigate if ventricular late potentials—small abnormal electrical signals linked to arrhythmias in other species—could be detected in horses using SAECG.
- Researchers wanted to understand how these electrical potentials vary in healthy horses, those with myocardial injury, and those with valvular abnormalities.
Methodology
- Subjects:
- 24 healthy Thoroughbred horses ranging from 2 to 31 years old.
- One horse with experimentally induced myocardial injury via bupivacaine (a local anesthetic known to cause heart cell damage).
- Three horses showing persistent pathological cardiac murmurs.
- Data Collection:
- High-resolution orthogonal ECG leads (X, Y, and Z axes) recorded electrical activity from different spatial directions.
- SAECG was used to process these signals to highlight tiny electrical potentials indicative of delayed ventricular activation.
- SAECG Parameters Analyzed:
- Filtered QRS duration (fQRS): duration of the main ventricular depolarization after filtering noise.
- LAS40: duration of low-amplitude signals (below 40 µV) at the terminal part of the QRS complex.
- RMS40 and RMS50: root mean square voltages measured over the last 40 ms or 50 ms of the filtered QRS; lower values may indicate scarred or fibrotic tissue.
Key Findings
- In healthy horses:
- fQRS duration increased with age, indicating slower or altered conduction possibly due to age-related changes.
- Older horses had longer LAS40 and lower RMS40 and RMS50 values, consistent with the presence of myocardial fibrosis, which can alter electrical conduction.
- In the horse with experimentally induced myocardial injury:
- Histopathology confirmed myocardial necrosis (dead heart tissue).
- SAECG showed prolonged fQRS and LAS40 and reduced RMS40 and RMS50, consistent with ventricular late potentials.
- This pattern suggests that SAECG detected the damaged ventricular tissue’s abnormal electrical activity.
- In horses with persistent pathological murmurs:
- SAECG parameters fell within the normal range seen in healthy horses.
- Indicates that valvular abnormalities alone do not significantly affect intraventricular conduction or generate late potentials.
Interpretation and Implications
- SAECG effectively identifies ventricular late potentials linked to structural heart changes such as fibrosis (scarring) and necrosis in horses.
- Age-related myocardial fibrosis in horses may be detectable through prolonged QRS duration and altered low-amplitude signal parameters in SAECG.
- Valvular disease without myocardial damage does not alter these SAECG parameters, separating conduction abnormalities from valvular problems.
- SAECG holds promise as a non-invasive screening tool for identifying horses at risk of lethal arrhythmias and sudden death, which could improve clinical monitoring and preventive strategies.
- Combining SAECG with other diagnostic methods could enhance risk assessment and early intervention in equine cardiac care.
Conclusion
- This study demonstrated that signal-averaged electrocardiography is a sensitive method for detecting subtle ventricular conduction abnormalities in horses.
- It underlines the potential for SAECG to be used in routine veterinary cardiology to help predict and prevent sudden cardiac death caused by lethal arrhythmias.
Cite This Article
APA
Seki N, Tochinai R, Sekizawa SI, Ohmura H, Ueno T, Fukuda K, Kuwahara M.
(2026).
Signal-averaged electrocardiography in horses: characteristics of ventricular late potentials in healthy Thoroughbreds and horses with cardiac abnormalities.
J Equine Sci, 37(2), 41-51.
https://doi.org/10.1294/jes.2.41 Publication
Researcher Affiliations
- Laboratory of Veterinary Pathophysiology and Animal Health, Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
- Laboratory of Veterinary Pathophysiology and Animal Health, Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
- Research Center for Food Safety, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
- Laboratory of Veterinary Pathophysiology and Animal Health, Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
- Sports Science Division, Equine Research Institute, Japan Racing Association, Tochigi 329-0412, Japan.
- Microbiology Division, Equine Research Institute, Japan Racing Association, Tochigi 329-0412, Japan.
- Clinical Veterinary Medicine Division, Equine Research Institute, Japan Racing Association, Tochigi 329-0412, Japan.
- Laboratory of Veterinary Pathophysiology and Animal Health, Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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