Effect of pregnancy and correlation of weight and heart rate with electrocardiographic parameters in the American Miniature Horse

Abstract

There are studies on electrocardiogram (ECG) in several breeds of horses, which highlights the growing importance of cardiology in this species. But few authors have addressed the influence of pregnancy on the cardiac physiology of the mare, and specifically, there are no studies on the Mini-horse breed, as well as no correlation of body weight (BW) and heart rate (HR) with electrocardiographic parameters in this breed. The aims of this study were to determine the effects of pregnancy on ECG parameters and to examine the relationships between these variables and body weight (BW) and heart rate (HR). A total of 203 animals were used, including 143 females (66 pregnant) and 60 males. Electrocardiographic examinations were performed by computerized electrocardiogram (TEB), and the parameters were evaluated in six leads in the frontal plane (Lead I, II, III, aVR, aVL and aVF) and base-apex (BA). BW was inversely proportional to HR, which in turn showed an inverse relationship with the duration of the P-wave and the PR and QT intervals. The P-wave amplitude (lead II) was higher in pregnant animals than in non-pregnant animals. The effect of reproductive status should be monitored by ECG throughout the entire gestational period. The 66 pregnant mares in this study were examined during the first third of their pregnancies, thus, few differences were observed between pregnant and non-pregnant animals.Keywords: horse, body weight, cardiology, heart rate, pregnancy RESUMO Existem estudos sobre eletrocardiograma (ECG) em diversas raças de equinos

Electrocardiographic Aspects of Singleton Pregnancy and Neonatal Period in American Miniature Horse Breed

“…It can be noted that the values of both P1 and P2 decreased as age progress. At 14th days of age, the values found for this parameter were similar to foals from 15 days to 10 months of age of the same breed [24].…”

“…However, comparing the duration of the PR segment and the QRS complex, numerically, the neonates in the present study had shorter time compared to the Ponies [10]. As for the duration of the T wave, the foals had presented lower values than those already described, which it is possibly due to the heterogeneous age of the foals [24].…”

“…The electrocardiography (ECG), with HR assessment and wave morphology [19], can assist in complete cardiac evaluation of pregnant mares and newborn foals [4], however, it is necessary to use the reference values for the miniature breeds, in addition to the age range and reproductive condition [6,7,14,24,25].…”

“…The ECG exams of 66 AMH mares in the initial third of the pregnancy showed few changes in relation to non-pregnant females, but the authors suggested progressive supervision on gestational period in order to elucidate the manifestations in ECG patterns [24].…”

“…Although widely used in the small animal internal medicine [27], studies on ECG in equine and foal fetuses are scarce. This exam can be an important tool in equine neonatology [12], as it is an accessible, non-invasive and easily performed technique in the field [24]. Several studies had been carried out in relation to ECG and other clinical parameters in foals, such as Thoroughbred [5,20,28] and Ponies [10].…”