Electrocardiography in the horse. (A report of findings in 138 horses).

This research paper examines the results of electrocardiograms (ECGs) performed on 138 horses over a period of approximately three years, detailing the types and frequencies of observed ECG abnormalities and their clinical importance. It also discusses the prevalence and significance of detected cardiac murmurs in these horses.

Research Methodology and Patients

• The study was carried out over approximately three years with 138 horses referred to the Medical Clinic as patients.
• These horses were examined using Electrocardiograms (ECG) which check the electrical activity of the heart to detect any abnormalities.

Findings

• Of the 138 horses, 22 (about 16%) presented with ECG alterations. Overall, these 22 ECGs demonstrated a total of 29 distinct ECG abnormalities.
• The most common alteration was an incomplete AV block, identified in 9 horses, comprising 31% of the ECG abnormalities found in this study.
• Wide, tent-shaped, and occasionally inverted T waves and ST segment deviations were observed in 5 ECGs from 7 horses. In 3 of these horses, both types of abnormalities were present and were associated with significant underlying illnesses such as colic, enteritis, pneumonia, and strangles, among others.
• Premature ventricular beats were found in 3 horses, with two having severe cardiovascular dysfunction and the third not demonstrating any signs of cardiac disease.
• Atrial fibrillation was observed in two horses, both of which were treated with chinidine sulphate. However, neither horse achieved a conversion back to regular sinus rhythm after treatment.
• Other ECG abnormalities detected in the study included parasystole (1 horse), sinus arrhythmia (2 horses), sinoatrial block (1 horse), and wandering pacemaker (1 horse).

Cardiac Murmurs

• Detectable cardiac murmurs were found in 26 horses (approximately 19% of the study population).
• In 15 of these horses, the murmurs were short, faint, and largely diastolic – these were not considered significant.
• However, 11 horses exhibited distinct, loud (grade 4 or 5) holosystolic or holodiastolic murmurs deemed pathological.
• Eight of these 11 horses showed actual signs of cardiac disease.

Cardiac Vector Distribution

• The cardiac vector distribution in horses with ECG abnormalities or murmurs did not show any systematic differences when compared to horses without any cardiac abnormalities.

Conclusion

• The study highlights the relevance of examining ECG results in horses referred to a medical clinic for diagnostics and treatment.
• Despite a notable rate of observed ECG alterations and cardiac murmurs, the frequency and types of those did not necessarily correspond to significant underlying cardiac disease.
• Further research is required to expand understanding of equine heart disease and improve accuracy in identifying and treating cardiac issues in horses.