Medtronic Reveal LINQ™ Devices Provide Better Understanding of Hibernation Physiology in the American Black Bear (Ursus Americanus)

Abstract

The American black bear (Ursus americanus) has been called a metabolic marvel6. In northern Minnesota, where we have conducted long-term physiological and ecological studies of this species, bears may remain in their winter dens for 6 months or more without eating, drinking, urinating or defecating and yet lose very little muscle mass2. We also found that hibernating black bears elicit asystolic events of over 30 seconds and experience an exaggerated respiratory sinus arrhythmia2. In this previous work we employed Medtronic Reveal® XT devices that required us to visit the den and temporarily extract the bear (under anesthesia) to download the stored data.4 Here we describe Medtronic’s latest generation of Insertable Cardiac Monitor (ICM), the Reveal LINQ™, which enables continuous transmission of data via a relay station from the den site3. Black bear hibernation physiology remains of high interest because of the multiple potential applications to human medicine. ICMs have been used for nearly two decades by clinicians as a critical diagnostic tool to assess the nature of cardiac arrhythmias in humans. Such devices are primarily implanted subcutaneously to record electrocardiograms. The device size, battery life and transmission capabilities have evolved in recent years. The first devices were relatively large and a programmer was needed to retrieve information during each clinical (or in our case, den visit). These devices were programmed to capture cardiac incidents such as asystolic events, arrhythmias and tachycardias and apply algorithms that ensure proper data collection: e.g. ectopy rejection and p-wave presence algorithms. The new generation Reveal LINQ was made to telemetrically transmit heart data from human patients, but we needed to develop a system to enable transmission from bear dens, which are remote (cannot easily be checked and adjusted) and are subject to extreme winter weather conditions. Besides the advantage of these devices transmitting data automatically, they are considerably smaller and thus less prone to rejection by the extraordinary immune system of the hibernating bear1.