Standardisation of electrocardiographic examination in corn snakes (Pantherophis guttatus)

Abstract

IntroductionCorn snakes are a very common pet reptile species, yet there is an absence of evidence-based literature standardising collection of ECG or detailing ECG deflection morphology in the normal animal. The authors describe a well-tolerated, reproducible technique and detail the cardiac cycle in terms of lead 2 equivalent waveforms and intervals.Animals29 adult corn snakes.Materials and methodsThis prospective study evaluated, under species-appropriate, standardised conditions, a technique for producing standard six-lead ECG tracings. Lead 2 equivalent cardiac cycles were described in detail and statistically analysed for sex, weight, length, heart rate and mean electrical axis.ResultsHigh-quality tracings demonstrated common ECG characteristics for this species, including no Q, S or SV waves, prolonged PR and RT intervals, rhythmic oscillation of the baseline, short TP segments, and a right displaced mean electrical axis. An influence of sex, weight or length on heart rate and mean electrical axis was not identified.ConclusionsTo the authors’ knowledge, this is the first study to describe a standardised technique for recording ECG in significant numbers of normal corn snakes. Ranges have been provided that may be of diagnostic value or form the basis for future development of reference intervals for this species.

Analysis of heart rate variability in corn snakes (Pantherophis guttatus)

“…As shown here, there was no significant difference in heart rate between male and female snakes. This finding agrees with that of Lewis et al (2020), who also reported no sex-related differences in heart rate in this species. In contrast, there were significant sex-related differences in several ECG parameters, including the P and T waves, QRS complex and PR interval.…”

“…However, there is little information on the cardiovascular physiology of this species. Lewis et al (2020) examined the cardiac electrical activity of P. guttatus and described the various waves (S, P and R) and intervals (PR, RT and TP) of the ECG in these snakes. These authors noted that the TP interval was particularly useful for evaluating stress in these snakes and that there were important differences when compared with the mammalian ECG.…”

Why are you talking with snakes? To get new evolutionary insights in cardiac electrophysiology!

“…Furthermore, ECGs in reptiles are quite variable. The T wave is commonly found to be very wide and of variable morphology even in the same species (Lewis et al, 2020), as already described in the 1960s (Valentinuzzi et al, 1969). In addition, reptiles are ectotherms and depend on their environmental temperature to regulate their core temperature.…”

Comparative electrocardiographic study of the Asian freshwater box turtle Cuora flavomarginata and the Asian yellow pond turtle Mauremys mutica using non‐invasive methods

“…In mammals, birds and some reptiles, such as snakes, the QRS complex in leads I, III and aVF are clearly recognisable. 6 , 21 Hence, it can be used to calculate the MEA. However, in the present study, the QRS complex amplitude in lead I was very small or buried in the baseline, which did not allow those signals to be interpreted in most of the turtles.…”

“…To calculate the angle of the MEA in the frontal plane, we measured the amplitude of the QRS complex in leads I and III or in leads I and aVF, then added the vector of both leads to obtain the resultant magnitude and direction. In mammals, birds and some reptiles, such as snakes, the QRS complex in leads I, III and aVF are clearly recognisable 6,21 . Hence, it can be used to calculate the MEA.…”