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 Table of Contents    
METHODS
Year : 2017  |  Volume : 49  |  Issue : 1  |  Page : 116-118
 

Noninvasive recording of electrocardiogram in conscious rat: A new device


1 Department of Physiology, KGMU, Lucknow, Uttar Pradesh, India
2 Department of Biotechnology, AKTU, Lucknow, Uttar Pradesh, India

Date of Submission19-Feb-2016
Date of Acceptance15-Dec-2016
Date of Web Publication27-Feb-2017

Correspondence Address:
Pradeep Kumar
Department of Physiology, KGMU, Lucknow, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0253-7613.201031

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 » Abstract 

Aim: Electrocardiogram (ECG) is an important tool for the study of cardiac electrophysiology both in human beings and experimental animals. Existing methods of ECG recording in small animals like rat have several limitations and ECG recordings of the anesthetized rat lack validity for heart rate (HR) variability analysis. The aim of the present study was to validate the ECG data from new device with ECG of anesthetized rat.
Materials and Methods: The ECG was recorded on student's physiograph (BioDevice, Ambala) and suitable coupler and electrodes in six animals first by the newly developed device in conscious state and second in anesthetized state (stabilized technique).
Results: The data obtained were analyzed using unpaired t-test showed no significant difference (P < 0.05) in QTc, QRS, and HR recorded by new device and established device in rats.
Conclusion: No previous study describes a similar ECG recording in conscious state of rats. Thus, the present method may be a most physiological and inexpensive alternative to other methods. In this study, the animals were not restrained; they were just secured and represent a potential strength of the study.


Keywords: Conscious, electrocardiogram, noninvasive recording, rat


How to cite this article:
Kumar P, Srivastava P, Gupta A, Bajpai M. Noninvasive recording of electrocardiogram in conscious rat: A new device. Indian J Pharmacol 2017;49:116-8

How to cite this URL:
Kumar P, Srivastava P, Gupta A, Bajpai M. Noninvasive recording of electrocardiogram in conscious rat: A new device. Indian J Pharmacol [serial online] 2017 [cited 2017 May 25];49:116-8. Available from: http://www.ijp-online.com/text.asp?2017/49/1/116/201031


The electrocardiogram (ECG) is the record of algebraic sum of the action potentials of myocardial fibers during the cardiac cycle.[1] Thus, the ECG is an important tool for the study of cardiac electrophysiology both in human beings and experimental animals. Cardiac electrophysiology is highly useful in clinical assessments of cardiovascular disorders and acutely sensitive to the various effects of chemical and drugs.[2]

Existing methods of ECG recording in small animals like rat have several limitations, which can influence the electrophysiological parameters. For example, some methods require anesthesia and other require surgical procedures for ECG electrode implantation. Methods using anesthesia (drugs) and surgical procedures may affect the heart rate (HR), rhythm and various segment, and intervals of ECG.[3],[4],[5] In addition, ECG recording of the anesthetized rat lacks validity for HR variability analysis.[6],[7]

Various authors suggested that ECG can be recorded using specially designed boxes, stages, and jacket fitted with electrodes.[8],[9] These devices require complicated proceedings. Therefore, development of noninvasive devices for ECG and blood pressure recording in conscious animal rat is need of the day. These devices must be free from anesthesia, surgical invasions, or implant of electrodes/transmitter. Although it has been claimed that telemetry method is the gold standard [10] for ECG recording in rats, this device is highly expensive and irrational for the developing countries like India. Hence, in the present study, we described a new device for ECG recording for conscious rat which is noninvasive and free from anesthesia. The aim of the present study was to validate the ECG data from conscious with an anesthetized rat.


 » Materials and Methods Top


The study was approved by institutional ethics committee (31/IAH/Pharma/14 dated 17/05/14) and conducted on six male Wistar rats (220–300 g), kept in wooden floored cages, in a room with temperature of about 27°C and 12 h day-night cycle. Animals were acclimatized in ambient conditions and protocol of our experimental laboratory for 1 week and procedures were performed in accordance with the CPCSEA guidelines.

Experimental Protocol

The ECG was recorded on student's physiograph (BioDevice, Ambala) and suitable coupler and electrodes in six animals first by the newly developed device in conscious state and secondly in anesthetized state (stabilized technique). Thereafter, the recorded data were compared for accuracy of new device. ECG was recorded in each animal (both in conscious and anesthetized state) at 9:30 am daily for 5 days.

Electrocardiogram Recording by New Device in Conscious Rat

A diagram of the developed device for ECG recording of conscious rat is shown in [Figure 1]a and [Figure 1]b. It comprised four separate strips of fabric hook and loop fasteners (Velcro) mounted on the block board of a small table. Animal (rat) was placed on the surface of the block board so that its feet were not in contact with each other. The rat was kept in stationary position by securing their body by Velcro as shown in [Figure 2] and one fine sheet of polyethylene was placed between two limbs for insulation. Disk electrodes were tied on palmer surface of clean shaven limbs of rat. The front limbs and left hind limb were used for recording of ECG in standard leads while the right hind limb was attached with grounded electrode. ECG was recorded on a student's physiograph machine moving at a speed of 50 mm/s at normal filtering. ECG parameters, i.e. RR interval, QRS duration, and QT interval were measured from the lead II and analyzed by one of the authors himself. ECG was recorded for 5 min in each group. The mean value of six consecutive waves was calculated.
Figure 1: (a) Reprensentative recording of electrocardiogram (unconscious rat). (b) Reprensentative recording of electrocardiogram (conscious rat)

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Figure 2: Conscious rat restrained for electrocardiogram recording with the noninvasive device

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Electrocardiogram Recording in Anesthetized Rat: Anesthetization of Rat

Animals were anesthetized with thiopental (50 mg/kg body weight) intraperitoneally [11] and secured on animal operation table for ECG recording. ECG was recorded on a student's physiograph machine moving at a speed of 50 mm/s at normal filtering. ECG parameters, i.e., RR interval, QRS duration, and QT interval were measured from the lead II using calipers. RR interval was recorded to calculate the HR using formula: number of RR interval (ECG small square) covered in 1 minute.

Statistical Analysis

All data are expressed as mean ± standard deviation; differences in data between two devices were calculated using GraphPad QuickCalcs (Graph Pad Software, Inc., La Jolla, CA 92037 USA).


 » Results Top


Typical ECG in lead II records obtained from the various rats are shown in [Figure 1]. Amplification was adjusted and paper speed was kept at 50 mm/s to obtain comprehensible waveforms in each animal. Electrocardiographic data obtained from the different animals are shown in [Table 1]. In lead II, thePwaves, QRS complexes, and T waves were observed. We were not able to quantify the S-T segment in the ECG recordings. The reliable method for correcting the QT interval for rate is the Bazett's formula [12] that is QTC = QT/√RR, where QTc is the QT interval corrected for rate and RR is the interval between two consecutive R-waves measured in milliseconds. HR was calculated from the ECG records and it was >300 bpm. The mean values of ECG findings are shown in [Table 1]. The data showed that the mean HR (bpm) was 365.80 ± 7.95 and 363.80 ± 13.27 in conscious and anesthetized rats, respectively. QTc (ms) was 72.72 ± 0.36 in animals recorded by new device, while it was 73.8 ± 0.56 (ms) in anesthetized animals. QRS was 56.220 ± 3.25 (ms) in ECG of conscious animal, and the value of QRS was 53.8 ± 5.48 (ms) in ECG of anesthetized animals. Our data demonstrated that there was no significant difference in QTc, QRS, and HR.
Table 1: Electrocardiogram parameters in conscious and unconscious rat

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 » Discussion Top


Adverse effects of drugs and toxicants on the heart often manifest as a change in the ECG.[13] The ECG has been used since years to assess human cardiovascular health. Electrocardiographic recordings usually help to detect abnormal myocardial action potential, conduction of impulse, disturbances in cardiac rate and rhythm, and altered autonomic activities.[2] The method described, in this study, has many advantages over existing methods for recording ECG in conscious laboratory animals. Only a time of a week is needed to be spent on training/acclimatization of animals for this recording procedure, i.e., securing their body by Velcro and attachments of electrodes to limbs. In this way, the animals remain in a natural sitting position and there are no restrain or stress. Although the principle of the new device is same as existing one, the recording technique is unique and it will be able to record the ECG in conscious rats. ECG recording in conscious rats rely either on surgical placing of electrodes or implanted transmitter type electrodes.[10] It has shown that inflammatory responses may alter the physiological parameters of ECG. Although anesthesia may influence the ECG parameters, our data revealed that there was no statistically significant difference.


 » Conclusion Top


No previous study describes such type of ECG recording in conscious state of rats. Thus, the present method may be a most physiological and inexpensive alternative to other methods. In our study, the animals were not restrained; they were just secured and represent a potential strength of the study. The usefulness of this method will be in assessing the effect of drugs/toxicity on the ECG and HR.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.

 
 » References Top

1.
Narayanaswamy S. High resolution electrocardiography. Indian Pacing Electrophysiol J 2002;2:50-6.  Back to cited text no. 1
    
2.
Kumar P, Goyal M, Agarwal JL. Effect of L- arginine on electrocardiographic changes induced by hypercholesterolemia and isoproterenol in rabbits. Indian Pacing Electrophysiol J 2009;9:45-52.  Back to cited text no. 2
    
3.
Deutschman CS, Harris AP, Fleisher LA. Changes in heart rate variability under propofol anesthesia: A possible explanation for propofol-induced bradycardia. Anesth Analg 1994;79:373-7.  Back to cited text no. 3
    
4.
Kato M, Komatsu T, Kimura T, Sugiyama F, Nakashima K, Shimada Y. Spectral analysis of heart rate variability during isoflurane anesthesia. Anesthesiology 1992;77:669-74.  Back to cited text no. 4
    
5.
Latson TW, McCarroll SM, Mirhej MA, Hyndman VA, Whitten CW, Lipton JM. Effects of three anesthetic induction techniques on heart rate variability. J Clin Anesth 1992;4:265-76.  Back to cited text no. 5
    
6.
Fateev MM, Sidorov AV, Grigor'eva MV, Rakov AA, Fateeva KM. Heart rate variability in conscious and anesthetized rats under the action of angiotensin converting enzyme inhibitors. Bull Exp Biol Med 2012;152:590-4.  Back to cited text no. 6
    
7.
Castiglioni P, Di Rienzo M, Radaelli A. Effects of autonomic ganglion blockade on fractal and spectral components of blood pressure and heart rate variability in free-moving rats. Auton Neurosci Basic Clin 2013;178:44-9.  Back to cited text no. 7
    
8.
Pereira-Junior PP, Marocolo M, Rodrigues FP, Medei E, Nascimento JH. Noninvasive method for electrocardiogram recording in conscious rats: Feasibility for heart rate variability analysis. An Acad Bras Cienc 2010;82:431-7.  Back to cited text no. 8
    
9.
Kumar P, Agarwal JL, Kumar A. Effect of long term oral administration of L-arginine on experimentally produced myocardial ischemia in rabbits. Indian J Physiol Pharmacol 2007;51:147-52.  Back to cited text no. 9
    
10.
Sgoifo A, Stilli D, Medici D, Gallo P, Aimi B, Musso E. Electrode positioning for reliable telemetry ECG recordings during social stress in unrestrained rats. Physiol Behav 1996;60:1397-401.  Back to cited text no. 10
    
11.
Hildebrandt IJ, Su H, Weber WA. Anesthesia and other considerations for in vivo imaging of small animals. ILAR J 2008;49:17-26.  Back to cited text no. 11
    
12.
Kmecova J, Klimas J. Heart rate correction of the QT duration in rats. Eur J Pharmacol 2010;641:187-92.  Back to cited text no. 12
    
13.
Farraj AK, Hazari MS, Cascio WE. The utility of the small rodent electrocardiogram in toxicology. Toxicol Sci 2011;121:11-30.  Back to cited text no. 13
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1]



 

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