Physiological ECG Value for Polish Half-Bred Anglo-Arab Horses

Abstract

The electrocardiographic examination was performed in 33 training horses (2-16 years of age, 11 males and 22 females). Einthoven and precordial leads (I, II, III, aVR, aVL, aVF, CV 1 , CV 2 ,CV 4 ) were used. The ECG was performed in resting horses and immediately after exercise (10 min walk, 15 min trot, 10 min canter) using a portable Schiller AT-1 3-channel electrocardiograph, with a paper speed of 25 mm sec -1 and a sensitivity of 10 mm . mV -1 . The heart rate, wave amplitudes, and duration time were estimated manually. All horses presented a significant increase in heart rate after exercise (rest 43.83 ±10.33 vs. exercise 73.2 ±14.8). QT intervals were significantly shortened in most of the leads. In resting horses, all P waves in the lead I were positive and almost all II, III and CV 4 leads were positive. Simple negative P wave dominated in aVR and only simple negative T wave was found in the leads I. The biphasic shape was observed. After exercise, the amplitude of P and T waves rose, however, clear changes were not observed in wave polarisation and form. In the absence of specific racial characteristics of the electrocardiogram in the Polish AngloArabians, electrocardiographic findings can be interpreted according to ECG standards adopted for horses.Key words: Anglo-Arab horses, heart, ECG physiological values.Though ECG method is one of the oldest cardiovascular diagnostic procedures, there is scarce information on electrocardiographic values in different horse breeds. In literature, the need to conduct electrocardiographic studies in horses considering racial specificity of equine ECG is emphasised (5, 10). ECG recordings provide less information in horses in comparison to human and other animal species. This is connected with wide-spread rapidly conducting Purkinje fibers in the ventricles in horses and solipedes. Individual Purkinje fibers activate the adjacent cells of heart muscle, causing its rapid depolarisation and resulting in simultaneous contraction.The aim of the study was to estimate normal ECG values for Polish Anglo-Arab horses. Material and MethodsThe study was carried out on 33 healthy halfbred Anglo-Arab horses of both sexes (11 males, 22 females), weighing 480-550 kg. The horses were aged between 2 and 16 years. All horses were subjected to a regular training and reared under the ordinary management. The horses were examined in the stable.No abnormalities were detected in clinical examination of the horses. Einthoven and precordial leads (I, II, III, aVR, aVL, aVF, CV 1 , CV 2 , CV 4 ) were used in ECG examination.Alligator clips fixed to the electrocardiographic leads were attached directly to the skin. The sites of the attachment of electrodes were cleaned with alcohol but not shaved and electrode paste was applied. The electrodes were placed over the elbow and knee and on the chest: right and left 5 intercostal spaces (i.c.s.), on the humeral join line, and on the sternum on the ventral midline directly over the xiphoid cartilage approximately 5 i.c.s. The forelimbs were ...