Prevalence of cardiac arrhythmias in poorly performing horses.

Objective Summary

• This study investigated the prevalence and types of cardiac arrhythmias in poorly performing racehorses using electrocardiography and cardiac troponin measurements.
• It found a high frequency of various arrhythmias linked to poor performance, highlighting the importance of early diagnosis and monitoring in racehorses.

Introduction and Purpose

• Electrocardiogram (ECG) abnormalities are frequently observed in racehorses and can negatively affect their athletic performance.
• The research aimed to analyze ECG abnormalities and determine the prevalence of different cardiac arrhythmias among poorly performing horses.
• The study also measured cardiac troponin levels, a biomarker indicative of cardiac injury or stress, to evaluate its association with arrhythmias.

Study Design and Methods

• This was a cross-sectional study conducted over one year (September 2023 – August 2024).
• Standard ECG recordings were performed on 114 adult horses identified as poorly performing.
• Ten horses without arrhythmias served as a control group for comparison.
• Cardiac troponin levels were measured in all horses to assess cardiac muscle injury or dysfunction.

Key Findings on Cardiac Arrhythmias

• Overall, 74 out of 114 horses (64.9%) exhibited at least one type of cardiac arrhythmia.
• Atrial fibrillation was the most common arrhythmia, found in 60 horses (52.63%).
• Other common abnormalities included left axis deviation and left ventricular hypertrophy, seen in 29 horses (25.44%).
• Conduction abnormalities included:
  • Atrioventricular (AV) block in 34 horses (29.82%)
  • QT interval prolongation in 54 horses (47.36%) and QTc prolongation in 50 horses (43.85%)
  • Bradycardia observed in 20 horses (17.54%)
  • ST-segment depression detected in 25 horses (21.93%)
  • Bundle branch blocks: left bundle branch block in 13 horses (11.40%) and right bundle branch block in 26 horses (22.81%)

Cardiac Troponin Findings

• Troponin levels were significantly elevated in horses with arrhythmias compared to those without, suggesting myocardial damage or stress linked to abnormal cardiac rhythms.

Demographic Observations

• The incidence of atrial fibrillation was significantly higher in male horses across all age groups except the oldest group.

Implications and Importance

• Cardiac arrhythmias can lead to intolerance to exercise and poor performance in racehorses, directly impacting their racing careers and wellbeing.
• Early diagnosis of these arrhythmias via ECG combined with measurement of cardiac troponin levels is crucial.
• Prompt identification allows veterinarians to develop appropriate long-term treatment or management strategies to improve performance and horse health.
• This study reinforces the utility of ECG and troponin biomarker screening in monitoring cardiac health in racehorses.