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Prevalence and diagnosis of cardiac arrhythmias in sport horses

Most heart disease in horses long tolerate them because diagnosis is necessary first of all in terms of the safety for humans and for prediction of animals performance. Horses cardiovascular system has significant compensatory abilities, so assessment of its condition must be performed during or after exercise, when latent disease manifests itself clinically.

In practical terms veterinary experts often diagnosed in sport horses variety of cardiac arrhythmias. Electrocardiography refers to the priority of the heart of the horses, as none of the clinical methods can not replace it in the diagnosis of cardiac arrhythmias in the animals.

It is believed that the horses are registered arrhythmias often compared with other types of animals, but in the literature there is a limited number of reports on their distribution and impact on the performance of the animals.

The aim was to investigate the distribution of cardiac arrhythmias in sport horses using electrocardiography and set of physiological and pathological arrhythmias. Research carried out by 46 sport Ukrainian horses warmblood horse, Hanoverian and Westphalian breeds aged 4–15 years, used in classical types of equestrian sport.

Record electrocardiogram (ECG) was performed using 3-channel electrocardiograph "Kardiostyl veterinarian" for 5 minutes at a speed of 50 mm/s, the device sensitivity 1 mV (10 mm). ECG recorded in standard (I, II, III) and enhanced (aVR, aVL, aVF) leads.

The red electrode is positioned in the lower third of the right jugular groove. The yellow electrode is positioned over the apex beat area of the heart, on the thorax, caudal to the left elbow. The green electrode can be positioned on the middle of the left scapula. The remaining black electrode positioned anywhere on the body surface of the horse. Lead II is recorded.

ECG recorded twice: once to the exercises, the second – immediately after its completion. The scheme exercises of medium intensity was 1:00: walk 5 min.; trot 10 min.; walk 5 min.; trot 10 min.; walk 10 min.; gallop 10 min.; walk 10 minutes.

As a result of electrocardiography performed before exercise in 71.7 % of horses had sinus rhythm. In 21.7 % of registered horses sinus arrhythmia, at 8.7 % – tachycardia. In 26.1 % of sport horses registered second degree AV block, 21.7 % – supraventricular premature complex (SVPC) and 4.3 % ventricular premature complex (VPC) that do not have clinical significance. Third degree AV block at rest were recorded in 1 animal that manifested clinical symptoms (reduced physical performance, loss of consciousness), because the animal was excluded from training.

After exercise sinus tachycardia detected in 19.6 % of horses, sinus arrhythmia – in 32.6 %. Increasing the number of horses after exercise tachycardia apparently due to lack of fitness of animals.

After exercise the second degree atrioventricular block disappeared in 13.0 %. In the recovery period it occurred again in 5 horses. This arrhythmia was considered pathological. After exercise of 34.8 % horses recorded SVPC and in 6.5 % of horses – VPC. In sport horses registered as wandering pacemaker, sinus pause and atrial fibrillation.

The use of electrocardiography in sport horses, especially with reduced capacity for work before and after exercise allows differentiating physiological from pathological arrhythmias. However, detection of arrhythmias in horses and their impact on the performance of the animals is still a matter of debate among scientists.

Key words: horses, exercise, electrocardiography, electrocardiogram, physiological and pathological arrhythmias, heart disease.

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