This work was supported by the Basic Science Research Programs that are managed by the National Research Foundation of Korea (NRF) (2015R1C1A2A01052419 and 2018R1D1A1B07042484).

All animal procedures were approved by the local committee for the Care and Use of Laboratory Animals, Kyung Hee University (license number: KHUASP(SE)-18-108) and conformed to the US National Institutes of Health Guide for the Care and Use of Laboratory Animals.
1. Experimental animals
<ol>
	<li>Keep all mice (39 mice, Balb/c, male, 7&#8210;9 weeks old) in a pathogen-free facility as per the guide for the care and use of laboratory animals.</li>
	<li>Maintain the mice on a 12 h light/dark c...

<ol>
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No conflicts of interest, financial or otherwise, are declared by the authors.

There are several critical steps in the protocol. The surrounding environment should be free from noise and vibration. The ECG electrodes must be inserted under the skin stably and consistently of which the insertion step requires preliminary experiments until the researcher is technically experienced. Further, the anesthetic should be prepared and stored appropriately and used at the proper dose. Finally, the PQRS waves should be located appropriately in individual ECG beats in the Averaging View window.
<p class="j...

The electrocardiogram (ECG), a test that measures the electrical activity of one&#8217;s heartbeat, is a valuable tool for evaluating the cardiac conduction system. The parameters that are measured by an ECG include heart rate, PR interval, QRS duration, and QT interval. In brief, PR interval corresponds to the time that is required for an electrical impulse to travel from the atrial sinus node through the atrioventricular node to the Purkinje fibers; QRS duration is the time for ventricular depolarization to occur through the Purkinje system and ventricular myocardium; and QT interval is the duration of ventricular repolarization.
ECG recordings in mice have helped researchers examine cardiac function and determine the physiological and pathophysiological mechanisms of cardiac phenotypes, such as arrhythmia, atrial fibrillation, and heart failure. Most cardiovascular research has involved studies in genetically engineered mouse models. It is often challenging to obtain meaningful data on ECG recordings from small mice that have been genetically manipulated.
There are several methods for performing ECGs in mice1. Studies suggest that ECG recordings in conscious animals are preferred over anesthetized animals when possible since the effects of anesthesia on cardiac function have been well established2. Two protocols that record ECG in conscious mice are of note1. The ECG radiotelemetry system is the gold standard for continuous long term monitoring of ECG in conscious mice1,3. Despite their strength in being recorded in a conscious state, radiotelemetry-coupled ECG measurements have several limitations, including the high expense for setup and for the implant, its requirement of a highly experienced operator, a stabilization period of over 1 week, its need for large mice (&#62; 20 g), and acquisition of only a single lead of ECG recording1. Another system that uses paw-sized conductive electrodes embedded in a platform allows ECG recordings in conscious mice without anesthesia or implants1,4. This non-invasive system is an alternative method in situations in which radiotelemetry systems are unavailable since it has many advantages: no requirement of surgical treatment, no need of anesthesia, low cost per mouse (only the initial setup is expensive), short time for measurement, and affordability of neonates1,4. The main disadvantage of this system is that it is not suited for continuous long term monitoring1.
Here we introduce another inexpensive, simple, and fast ECG recording method in anesthetized mice and demonstrate its validity and sensitivity by performing an ECG after autonomic blockade/stimulation of the cardiac conduction system. We suggest this ECG method for screening the effects of pharmacological agents, genetic modifications, and disease models in mice.

<table>
	<tbody>
		<tr>
			<td>2,2,2-tribromoethanol</td>
			<td>Sigma-Aldrich</td>
			<td>T48402-25G</td>
			<td>anesthetics, Avertin</td>
		</tr>
		<tr>
			<td>Animal</td>
			<td>Japan SLC, Inc., Shizuoka, Japan</td>
			<td></td>
			<td>Balb/c mice, male, aged 7-9 weeks</td>
		</tr>
		<tr>
			<td>Atropine</td>
			<td>Sigma-Aldrich</td>
			<td>A0123</td>
			<td>parasympathetic antagonist</td>
		</tr>
		<tr>
			<td>BioAmp</td>
			<td>AD Instruments, Bella Vista, Australia</td>
			<td>ML132</td>
			<td>bio amplifier</td>
		</tr>
		<tr>
			<td>Carbachol</td>
			<td>Sigma-Aldrich</td>
			<td>C4382</td>
			<td>parasympathetic agonist</td>
		</tr>
		<tr>
			<td>Electrodes with acupuncture needles</td>
			<td>DongBang Acupuncture Inc., Sungnam, Korea</td>
			<td>DB106</td>
			<td>0.20 x 15 mm</td>
		</tr>
		<tr>
			<td>Isoprenaline</td>
			<td>Sigma-Aldrich</td>
			<td>I2760</td>
			<td>sympathetic agonist</td>
		</tr>
		<tr>
			<td>LabChart 8</td>
			<td>AD Instruments, Bella Vista, Australia</td>
			<td></td>
			<td>data analysis software</td>
		</tr>
		<tr>
			<td>Mouse food</td>
			<td>LabDiet, St. Louis, MO, USA</td>
			<td>5L79</td>
			<td>Mouse diet</td>
		</tr>
		<tr>
			<td>PowerLab 2/28</td>
			<td>AD Instruments, Bella Vista, Australia</td>
			<td></td>
			<td>data acquisition system</td>
		</tr>
		<tr>
			<td>Propranolol</td>
			<td>Sigma-Aldrich</td>
			<td>P0884</td>
			<td>sympathetic antagonist</td>
		</tr>
		<tr>
			<td>SPSS Statistics program</td>
			<td>SPSS</td>
			<td>SPSS 25.0</td>
			<td>statistics program</td>
		</tr>
	</tbody>
</table>

electrocardiogram recordings in anesthetized mice using lead ii

The electrocardiogram is a valuable tool for evaluating the cardiac conduction system. Animal research has helped generate novel genetic and pharmacological information regarding the electrocardiogram. However, making electrocardiogram measurements in small animals in vivo, such as mice, has been challenging. To this end, we used an electrocardiogram recording method in anesthetized mice with many advantages: it is a technically simple procedure, is inexpensive, has short measuring time, and is affordable, even in young mice. Despite the limitations with using anesthesia, comparisons between control and experimental groups can be performed with enhanced sensitivity. We treated mice with agonists and antagonists of the autonomic nervous system to determine the validity of this protocol and compared our results with previous reports. Our ECG protocol detected increased heart rates and QTc intervals on treatment with atropine, decreased heart rates and QTc intervals after carbachol treatment, and higher heart rates and QTc intervals with isoprenaline but did not note any change in ECG parameters on administration of propranolol. These results are supported by previous reports, confirming the reliability of this ECG protocol. Thus, this method can be used as a screening approach to making ECG measurements that otherwise would not be attempted due to high cost and technical difficulties.

Pharmacological experiments
To determine whether our noninvasive ECG measurement reflects the influence of autonomic modulation on the cardiac conduction system, normal Balb/c mice were challenged with agonists and antagonists of the autonomic nervous system (ANS). Atropine and carbachol were used to effect parasympathetic autonomic blockade and stimulation, respectively, whereas propranolol and isoprenaline were administered to elicit sympathetic autonomic blockade and stimul...

Watch this Scientific Journal Video about Electrocardiogram Recordings in Anesthetized Mice using Lead II at JoVE.com

Electrocardiogram Recordings in Anesthetized Mice using Lead II

We present an ECG protocol that is technically easy, inexpensive, fast, and affordable in small mice, and can be performed with enhanced sensitivity. We suggest this method as a screening approach for studying pharmacological agents, genetic modifications, and disease models in mice.

The electrocardiogram is a valuable tool for evaluating the cardiac conduction system. Animal research has helped generate novel genetic and ...

The significance of our protocol is that the electrocardiogram measurement can be performed with great sensitivity in a small mouse that has been manipulated genetically or pharmacologically. The protocol is advantageous in that it is simple, fast, inexpensive, and sensitive. Additionally, it can be performed on small mice, even neonates.We believe that this method would contribute to the understanding of unexplored regions of arrhythmia in the cardiovascular area. Demonstrating the procedure will be Tae Woong Ha from my laboratory. Begin by opening the analysis software and setting it up for ECG data acquisition.Go to Setup and Channel Settings and set the Sample Rate to 2, 000 samples per second. Set the range to 20 millivolts and the input amplifier to 200 Hertz of low pass. Next, go to ECG Analysis and ECG Settings, then choose Mouse in the Preset of Detection and Analysis Settings.In the Averaging panel, choose to concatenate and consecutive cardiac cycles into a single average signal or averaging view and a table view. In the QTc panel, select the Bazett method, which is defined as the heart rate corrected value of QT interval. Place the mouse on the precision scale and record its weight.After ensuring that the mouse is properly anesthetized insert electrodes with acupuncture needles into the right and left forelimbs and the left hindlimb. Make sure that electrode depth and position are consistent throughout the experiments. Connect the other ends of the electrodes by clicking them into the three snap connectors at the other end of the lead wires of the three lead bio amplifier cable and inject drugs approximately three minutes after the anesthetics.10 minutes after administering anesthetics, begin recording the ECG. Once the recording is completed, use the ECG data from 12 to 17 minutes after injection of anesthetics for analysis. When finished, carefully remove the electrodes.To determine whether this noninvasive ECG measurement reflects the influence of autonomic modulation on the cardiac conduction system, normal BALB/c mice were challenged with agonists and antagonists of the autonomic nervous system. Compared to vehicle control, heart rate increased significantly in atropine and isoprenaline treated mice and fell with carbachol. In addition, the QTc interval rose in atropine and isoprenaline treated mice and decreased in carbachol treated mice.Representative chart views and averaging views of the ECG signals in atropine, carbachol and vehicle treated mice are shown here. When attempting this protocol, the most important thing is to ensure that the ECG electrodes are securely inserted throughout the experiment. Perform multiple preliminary experiments until the ECG signals are stable and consistent.Our previous publications with mice confirmed ECG variations that had been reported in human genetic studies, which supports the utility of this method in cardiovascular research areas such as arrhythmia.

electrocardiogram-recordings-in-anesthetized-mice-using-lead-ii

Research

JoVE Journal

Medicine

11.8K visualizações.  Kyung Hee University. O significado do nosso protocolo é que a medição do eletrocardiograma pode ser realizada com grande sensibilidade em um pequeno rato que foi manipulado geneticamente ou farmacologicamente. O protocolo é vantajoso, pois é simples, rápido, barato e sensível. Além disso, pode ser realizado em ratos pequenos, até mesmo neonatos.Acreditamos que esse método contribuiria para a compreensão de regiões inexploradas de arritmia na área cardiovascular. Demonstrando o procedimento ser...