Standard Electrocardiographic Data of Peccaries (Tayassu tajacu)

Abstract

Background:Peccaries (Tayassu tajacu, Linnaeus, 1758) are wild suiformes that belong to the Tayassuidae family. Electrocardiography is an important technique for cardiovascular evaluation. Analysis of various intervals, segments, complexes and waveforms of electrocardiographic (ECG) traces aids in the diagnosis of cardiac alterations and in the differentiation of congenital and acquired heart diseases from physiological cases. However, in wild animal medicine, the various patterns of normality and the evaluation of electrical traces associated with heart disease have not yet been sufficiently elucidated. The purpose of this study was to characterize the electrocardiographic (ECG) traces of peccaries sedated using ketamine and xylazine.

Materials, Methods & Results:Fourteen healthy adult animals that were subjected to digital ECG examination were used. Animals with evidence of systemic diseases, cardiovascular abnormalities (murmurs or arrhythmias), or any degree of valve insufficiency observed on echocardiogram and animals that exhibited excessive stress during the examination were excluded from the study. All animals presented with a normal sinus rhythm. A combination of 15 mg/kg of ketamine hydrochloride and 3 mg/kg of midazolam maleate was applied intramuscularly for chemical immobilization. The animals were manipulated after 15 min, when the onset of the anaesthetic effect was verified, for a duration of 45 min, and no reinforcement dose was necessary to complete the electrocardiographic examination.  No significant differences were observed in the P-wave duration, PR interval and QT interval between genders (P > 0.05). No significant differences were found between the amplitudes of the P and R waves between males and females (P > 0.05). The observed P waves were small, monophasic and positive. The QRS complex was positive in the DI, DII, DIII, aVF, V4 and V10 derivations and negative in the aVR, aVL, V1 and V2 derivations. In 71% of the animals, the T wave showed negative polarity in the DI, DII, DIII, aVL, aVF, and V10 derivations and positive polarity in the aVR, V1, V2 and V4 derivations. The ST segment was isoelectric in 100% of the animals. GraphPad Prism 7 (La Jolla, CA, USA) software was used to analyze the data, with non-parametric tests used to test for differences in the variables between the sexes. In these tests, a P-value of 0.05 was considered to indicate statistical significance.

Discussion:Although studies on the cardiac electrophysiology of wild animals have previously shown good results for several species, this is the first study concerning the standardization ECG traces for peccaries. However, due to the wild nature of these animals, their manipulation for handling and data collection purposes is only feasible under chemical containment, although other studies have used non-anaesthetized agoutis. It is not known to what extent these results may have been influenced by the effects of stress. Drugs used for this function may have direct effects on cardiac function. Therefore, the presumed normal ECG values, as well as the recognition of changes due to drug or iatrogenic interactions, are of fundamental importance.  This protocol provided high-quality anaesthetized peccary ECG traces, allowing reliable measurements of waves and intervals and assessment of the cardiac rhythm and heart rate. The surface registry digital ECG recording technique used with chemical containment allowed good monitoring and rapid acquisition and was well tolerated by the animals.