Name: real-time electrocardiogram monitoring during treadmill training in mice
Uploaded: 2022-05-05T15:00:00
Description: Watch this Scientific Journal Video about Real-Time Electrocardiogram Monitoring During Treadmill Training in Mice at JoVE.com

This work was supported by the German Research Foundation (DFG; Clinician Scientist Program in Vascular Medicine (PRIME), MA 2186/14-1 to P. Tomsits), the German Centre for Cardiovascular Research (DZHK; 81X2600255 to S. Clauss), the Corona Foundation (S199/10079/2019 to S. Clauss), and the ERA-NET on Cardiovascular Diseases (ERA-CVD; 01KL1910 to S. Clauss). The funders had no role in manuscript preparation.

All animal procedures were conducted in accordance with the guidelines of the Animal Care and Ethics committee of the University of Munich and all procedures were approved by the Government of Bavaria, Munich, Germany (ROB-55.2-2532.Vet_02-16-200). Four male wildtype in-house bred C57BL/6N mice were used in this study.
1. Preparation and surgical implantation of the transmitter
NOTE: For a detailed protocol of transmitter preparation and implantation ...

Current guidelines recommend regular physical activity as it has been demonstrated to be an important modifier of cardiovascular risk factors30. There is also a growing body of evidence that moderate physical activity may protect against atrial fibrillation (AF) both in primary and secondary prevention31,32,33. On the contrary, endurance athletes such as marathon runners have a higher risk to develop AF i...

Regular physical activity is important for a healthy life. Certain cardiovascular conditions, however, lead to situations where this common-sense agreement is at least questionable. In patients with myocarditis, current data even shows adverse effects of exercise and, thus, it is recommended to pause all exercise for a certain period in these patients1,2,3. In other cardiovascular diseases (CVD) such as inherited arrhythmia syndromes comparatively less evidence on the appropriate level of exercise exists4,5,6,7, making clinical counselling in these cases, mostly for young and physically active patients, very challenging.
Adverse remodeling leading to reduced contractility and heart failure and proarrhythmogenic remodeling leading to arrhythmias and sudden cardiac death have been suggested as hallmarks of exercise-associated harmful effects on the heart8. A large number of studies indicate beneficial effects of moderate exercise over a broad spectrum of different diseases9,10. Extensive training, however, may have detrimental effects on the heart leading to arrhythmias especially in otherwise healthy athletes11. Although structural remodeling processes leading to a vulnerable proarrhythmic substrate production may underlie this paradox situation as demonstrated in marathon runners12, the specific mechanisms of exercise-related adverse remodeling both in healthy people and in patients with cardiovascular diseases remain largely unknown.
In animals, especially in mice, several suitable models have been developed to mimic a broad range of cardiovascular diseases13,14. Also, various exercise models and training protocols have been established in mice15,16,17, including motorized treadmill training, voluntary wheel running (VWR), and swimming17,18. Evaluation of cardiac electrophysiology by ECG monitoring classically depends on a direct conducting connection between the animal and some sort of detection device. Thus, either animals need to be anesthetized, e.g., to obtain ECG recordings using sharp electrodes19, or animals need to be immobilized by a restrainer 20, or data quality is reduced due to motion artifacts, e.g., when using paw-electrodes21 or conductive platforms22 allowing only basic analysis. Thus, none of the above-mentioned approaches are compatible with training protocols and consequently prevent studies on exercise-related mechanisms leading to adverse remodeling in mice. Implantable telemetry devices can overcome these hurdles and are nowadays the most powerful tool and gold standard to evaluate murine electrophysiology in vivo in conscious and moving animals23,24. Current telemetry hardware solutions have been developed to monitor mice in their cages25,26,&#160;and commonly require a receiver to be placed underneath the cage for data acquisition, thus making real-time monitoring outside these circumstances challenging. Here we provide an approach to investigate the effects of exercise on cardiac electrophysiology and arrhythmogenesis by real-time ECG recording during treadmill training in mice using implanted telemetry devices. All parameters obtained were analyzed as previously described by Tomsits et al.23.

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			<td>Data Exchange Matrix 2.0 (MX2)</td>
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			<td>Manages communication between PhysioTel and PhysioTel HD telemetry implants and the acquisition computer.</td>
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			<td>Modified Bain circuit</td>
			<td>Hugo Sachs Elektronik</td>
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			<td>Data Science International</td>
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			<td>Connecting cables between Reciever, Signal Interface and Matrix 2.0 (MX2)</td>
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			<td>Amplifier for recording Surface ECG</td>
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			<td>PhysioTel ETA-F10 transmitter</td>
			<td>Data Science International</td>
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			<td>PhysioTel receiver RPC-1</td>
			<td>Data Science International</td>
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			<td>Ponemah 6.42</td>
			<td>Data Science International</td>
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			<td>Powerlab</td>
			<td>ADInstruments</td>
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			<td>Suface ECG Acquisition hardware device. Includes ECG electrode leads</td>
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			<td>Prism 8.0.1</td>
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			<td>Radio Device (Sony AF/AM)</td>
			<td>Sony</td>
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			<td>Data Science International</td>
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real-time electrocardiogram monitoring during treadmill training in mice

Regular physical exercise is a major contributor to cardiovascular health, influencing various metabolic as well as electrophysiological processes. However, in certain cardiac diseases such as inherited arrhythmia syndromes, e.g., arrhythmogenic cardiomyopathy (ACM) or myocarditis, physical exercise may have negative effects on the heart leading to a proarrhythmogenic substrate production. Currently, the underlying molecular mechanisms of exercise-related proarrhythmogenic remodeling are largely unknown, thus it remains unclear which frequency, duration, and intensity of exercise can be considered safe in the context of disease(s).
The proposed method allows to study proarrhythmic/antiarrhythmic effects of physical exercise by combining treadmill training with real-time monitoring of the ECG. Implantable telemetry devices are used to continuously record the ECG of freely moving mice over a period of up to 3 months both at rest and during treadmill training. Data acquisition software with its analysis modules is used to analyze basic ECG parameters such as heart rate, P wave duration, PR interval, QRS interval, or QT duration at rest, during and after training. Furthermore, heart rate variability (HRV) parameters and occurrence of arrhythmias are evaluated. In brief, this manuscript describes a step-by-step approach to experimentally explore exercise induced effects on cardiac electrophysiology, including potential proarrhythmogenic remodeling in mouse models.

Depending on individual research objectives, subsequent analysis of obtained telemetry data will differ widely. Here, we demonstrate feasibility of the method by obtaining good quality data recorded during training periods and provide exemplary results of ECGs and heart rate variability analyses before, during, and after training. Data are presented as mean &#177; standard error of mean (SEM), all statistical analyses were conducted with a suitable statistical software (see Table of Materials). Statistic...

Watch this Scientific Journal Video about Real-Time Electrocardiogram Monitoring During Treadmill Training in Mice at JoVE.com

Real-Time Electrocardiogram Monitoring During Treadmill Training in Mice

Electrocardiogram (ECG) is the key variable to understanding cardiac electrophysiology. Physical exercise has beneficial effects but may also be harmful in the context of cardiovascular diseases. This manuscript provides a method of recording real-time ECG during exercise, which can serve to investigate its effects on cardiac electrophysiology in mice.

Regular physical exercise is a major contributor to cardiovascular health, influencing various metabolic as well as electrophysiological processes. ...

Real-time assessment of marine electrophysiological properties during training has been challenging so far. This protocol provides an approach to overcome this by allowing real-time ECG monitoring before, during and after treadmill training. Combining treadmill training and real-time ECG monitoring allows to gain new insights into the relationship between exercise and arrhythmias, especially in inherited arrhythmia syndromes using transgenic mouse models.The method in itself is straightforward but needs careful attention during transmitter implantation and electrical lead positioning to ensure good signal to noise ratio. Aparna Chivukula and Kavi Raj Chataut, two PhD students in my lab will demonstrate the procedure. Activate the transmitter by placing the supplied magnet in close proximity.Following activation, test the signal from the transmitter using a radio device at 530 hertz AM frequency, a sharp and clear beep indicates the transmitter is activated, whereas an inactivated transmitter does not give any signal. Switch on the treadmill. Set the treadmill slope, speed and shock intensity according to the training protocol.Press on Settings in the control unit and select Grid Test. This opens a grid size selection screen. Select Mice.Press on Start to begin the shock test. To begin the test, confirm the warning by touching the screen. Place the conductive part of the sponge accessory provided with the treadmill on the grid of the treadmill.Place it until the word pass"appears on the screen. Test all grids like this. The test will end automatically after all lanes successfully pass it, but can be stopped anytime by the user by pressing the Stop button.To continue with the cleaning test, press Start and wait for the test to run. Transfer the animal to the running compartment. Place the signal receiver on the transparent box and connect the signal receiver via the connecting cable to the data acquisition system, which consists of a data exchange matrix and a signal interface, which in turn connects to a computer with the acquisition software running to view the ECG signal during the experiment.Press Start to enter the running mode. Upon completion, remove the signal receiver from the transparent box and place it back underneath the cage as shown. Turn off the treadmill to avoid any unwanted shocks.Electrocardiogram data with clear P, Q, R, S and T waves in animals during training was obtained. Heart rate increases to around 800 beats per minute when the animal is exercising, and gradually recovers toward baseline after training. PR interval, QRS duration, and QTc intervals shorten under stress, and once the stress is over, return to baseline.Detection of tachycardia and bradycardia episodes shows sinus rhythm at baseline and sinus tachycardia during training. Heart rate increases during training and gradually returns to baseline post-training. This trend can also be visualized by the median RR interval.A comparable standard deviation of RR intervals was obtained at baseline and during training by automated RR annotation, demonstrating data quality. One of the most critical steps is the positioning of the signal receiver on the transparent box to ensure good signal to noise ratio.

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