Abstract
Background:
Electrocardiogram abnormalities are common in racehorses and can affect performance.

Aim:
This study aimed to analyze the results of electrocardiographic problems and measure the frequencies of various cardiac arrhythmias.

Methods:
This cross-sectional study was conducted between September 2023 and August 2024. Standard electrocardiographic recordings were obtained from all horses, and cardiac troponin levels were measured. Out of the 114 poorly performing adult horses, 10 cases without arrhythmia were considered the control group. Seventy-four horses (64.9%) had at least one type of cardiac arrhythmia, 60 (52.63%) had atrial fibrillation, and 29 (25.44%) had left axis deviation and left ventricular hypertrophy.

Results:
The most frequent conduction anomaly was atrioventricular block in 34 horses (29.82%), followed by QT prolongation in 54 horses (47.36%), and QTc prolongation in 50 horses (43.85%). Bradycardia was detected in 20 (17.54%) horses, and ST-segment depression was present in 25 (21.93%) horses. Conduction disturbances, including left bundle branch block in 13 horses (11.40%) and right bundle branch block in 26 horses (22.81%). Troponin levels were significantly elevated in cases of arrhythmia. The incidence of atrial fibrillation was significantly higher in male horses in all age groups except the oldest.

Conclusion:
Because cardiac arrhythmia may lead to racehorse exercise intolerance and suboptimal performance, early diagnosis is important to allow veterinarians to develop long-term treatment strategies. Furthermore, electrocardiography, along with cardiac biomarker cardiac troponin, is essential.

Key words: Arrhythmia; Electrocardiography; Horse.