No effect of season on the electrocardiogram of long-eared bats (Nyctophilus gouldi) during torpor

Original Paper

Abstract

Heterothermic animals regularly undergo profound alterations of cardiac function associated with torpor. These animals have specialised tissues capable of withstanding fluctuations in body temperature > 30 °C without adverse effects. In particular, the hearts of heterotherms are able to resist fibrillation and discontinuity of the cardiac conduction system common in homeotherms during hypothermia. To investigate the patterns of cardiac conduction in small insectivorous bats which enter torpor year round, I simultaneously measured ECG and subcutaneous temperature (Tsub) of 21 Nyctophilus gouldi (11 g) during torpor at a range of ambient temperatures (Ta 1–28 °C). During torpor cardiac conduction slowed in a temperature dependent manner, primarily via prolongation along the atrioventricular pathway (PR interval). A close coupling of depolarisation and repolarisation was retained in torpid bats, with no isoelectric ST segment visible until animals reached Tsub <6 °C. There was little change in ventricular repolarisation (JT interval) with decreasing Tsub, or between rest and torpor at mild Ta. Bats retained a more rapid rate of ventricular conduction and repolarisation during torpor relative to other hibernators. Throughout all recordings across seasons (> 2500 h), there was no difference in ECG morphology or heart rate during torpor, and no manifestations of significant conduction blocks or ventricular tachyarrhythmias were observed. My results demonstrate the capacity of bat hearts to withstand extreme fluctuations in rate and temperature throughout the year without detrimental arrhythmogenesis. I suggest that this conduction reserve may be related to flight and the daily extremes in metabolism experienced by these animals, and warrants further investigation of cardiac electrophysiology in other flying hibernators.

Keywords

Arrhythmia Heart Electrocardiogram Metabolism Thermoregulation 

Notes

Acknowledgements

I would like to thank Fritz Geiser, Jack Tatler and Philip Currie for their helpful comments on the manuscript. This research was supported by a University of New England Postdoctoral Research Fellowship, Sagol School of Neuroscience Postdoctoral Fellowship and a Faculty of Life Sciences Postdoctoral Fellowship from Tel Aviv University.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Centre for Behavioural and Physiological Ecology, ZoologyUniversity of New EnglandArmidaleAustralia
  2. 2.Department of Zoology, Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael

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