Name: transthoracic echocardiographic examination in the rabbit model
Uploaded: 2019-06-01T14:00:00
Description: Watch this Scientific Journal Video about Transthoracic Echocardiographic Examination in the Rabbit Model at JoVE.com

This work was supported in part by: Fundaci&#243;n S&#233;neca, Agencia de Ciencia y Tecnolog&#237;a, Regi&#243;n de Murcia, Spain (JT) (Grant number: 11935/PI/09) and the University of Reading, United Kingdom (AG, GB) (Central Funding). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

The experiments described herein were approved by the Ethical Research Committee of the University of Murcia, Spain, and were performed in accordance with Directive 2010/63/EU of the European Commission. The steps described were performed under standard operating protocols that were part of the plan of work and have not been performed solely for the purpose of filming the accompanying video to this paper.
1. Preparation of the rabbit
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	<li>Before proceeding, start by injecting a combinat...

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We have described a protocol for the echocardiographic examination of cardiac function parameters in the rabbit, representing a large preclinical model1,2,3. The step by step methodology described herein should be considered guidance, which with a complementary study of the basic principles of echocardiography, and a basic knowledge of ultrasound imaging, will help the researcher to obtain, through practice and complementary and...

Longitudinal evaluation of cardiac function in large animal models is a robust research methodology commonly used for the assessment of the effects of novel therapies for treating ischemic and non-ischemic cardiomyopathy. Amongst the several cardiovascular imaging techniques available for preclinical research, echocardiography has been used extensively because of its non-invasive and portable characteristics. In experienced hands, echocardiography is also a very reproducible imaging technique to study cardiac anatomy as well as systolic and diastolic function of the heart.
Large preclinical animal models such as pigs, dogs and rabbits, are paramount for preclinical translational research1,2,3. Indeed, the potential benefit of novel therapies such as cardiac regenerative medicine in the setting of cardiomyopathy requires extensive hypothesis testing in large preclinical models before they can be considered for human use2,4. Compared to other large preclinical models, the rabbit model offers some advantages, including its low maintenance cost, which is comparable to that of mice and rats. However, in contrast to mice and rats, the Ca+2 transport system and cardiac electrophysiology are similar in rabbits as those of humans, and those of other large animal models such as dogs and pigs, thus increasing the translational potential of the rabbit model1,5. Therefore, the rabbit, as a large experimental preclinical model, has an exceptional balance of cost and reproducibility for preclinical translational research.
The rabbit has the additional benefit of its amenability for echocardiographic imaging using clinical ultrasound units routinely used in human and veterinary patients, thus taking advantage of the superiority of harmonic imaging and state-of-the-art technology. For this, sector transducers (also known as phase array) of relatively high frequency (up to 12 MHz), such as those used in neonatal/pediatric cardiology, are preferred. Echocardiographic examination in the rabbit preclinical model allows the complete evaluation of systolic and diastolic function using multiple views and different modes available in modern echocardiographic units (e.g. continuous wave Doppler (CWD), pulsed-wave Doppler (PWD), and Tissue Doppler imaging (TDI)).
Echocardiography is an operator-dependent technique and therefore requires extensive training and core knowledge of the technique in accord with international guidelines. Part of this training can be facilitated with the visualization of videos explaining in detail how different echocardiographic views can be obtained. The achievement of high competency in echocardiographic imaging, as well as development of a standardized protocol and correct technique, are essential to minimize the influence of the operator and to generate reliable quantitative data, as required in rigorous scientific research.
Some considerations are necessary regarding the system and laboratory setup used for echocardiography in rabbits and other large animal models. For a standard transthoracic echocardiographic evaluation of cardiac function, the ultrasound system must include the following modalities: bi-dimensional mode (B-mode or 2D), motion mode (M-mode), color Doppler, as well as CWD, PWD and TDI. Moreover, the machine should have full cardiac analysis and measurement software installed, as well as sufficient internal hard drive space to store enough high quality digital still images and video loops for offline analysis. Some systems use linear array transducers; however, for the best imaging of the heart, phased array sector transducers with a small scan head diameter are preferred, because these allow an easier passage of the ultrasound waves through the narrow intercostal spaces. For rabbits, we use relatively high frequency transducers (up to 12 MHz). The position of the animal for imaging is of utmost importance to acquire good quality images. Thus, both right and left lateral recumbent positions are recommended to obtain all standard imaging planes during an echocardiographic examination. For this, a table with a notch that coincides with the cardiac area of the chest is advisable (Figure 1A). This notched table facilitates the access with the transducer to the area of the chest that will be scanned, and therefore allows free mobility of the hand of the operator whist maintaining the best scanning position of the animal. Positioning the animal in a lateral recumbent position results in a fall of the heart towards the transducer and elevation of the lungs, as well as widening the access window of the ultrasound beam through the intercostal spaces, thus improving overall imaging quality (Figure 1A). The echocardiographic examination should be performed in a blinded fashion and following the guidelines of the Echocardiography Committee of the American College of Veterinary Internal Medicine and the American Society of Echocardiography/European Association for Cardiovascular Imaging6,7,8.
Part of our scientific team is associated with the Cardiology Service of a Veterinary Teaching Hospital that attends daily to veterinary patients (e.g. dogs and cats), for which it has the relevant training and accreditation in veterinary cardiology and echocardiography, and its different imaging modalities, as well as extensive experience in imaging different sizes of animal patients and thoracic conformations with this technique. In addition, we commonly use echocardiography for longitudinal evaluation of cardiac function in a rabbit model of cardiomyopathy induced by anthracyclines9. Here, we describe a step by step echocardiography protocol for evaluation of cardiac function using a clinical ultrasound unit in a large preclinical model such as the rabbit. This protocol is adapted for current international guidelines8, and includes practical recommendations based on our own experiences in clinical and experimental settings.

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	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Bluesensor</td>
			<td style="width:135px;">Medicotest</td>
			<td style="width:187px;">13BY1062</td>
			<td style="width:267px;">Disposable adhesive ECG lectrodes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Domtor (Medetomidine)</td>
			<td style="width:135px;">Esteve</td>
			<td style="width:187px;">CN 570686.3</td>
			<td>Veterinary prescription is necessary</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:327px;">HD11 XE Ultrasound System</td>
			<td style="width:135px;">Philips</td>
			<td style="width:187px;">10670267</td>
			<td>Echocardiography system.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:327px;">Heating Pad</td>
			<td style="width:135px;">Solac</td>
			<td style="width:187px;">CT8632</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Imalgene (Ketamine)</td>
			<td style="width:135px;">Merial</td>
			<td style="width:187px;">RN 9767</td>
			<td>Veterinary prescription is necessary</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Omnifix-F 1 ml syringe</td>
			<td style="width:135px;">Braun</td>
			<td style="width:187px;">9161406V</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:327px;">S12-4</td>
			<td style="width:135px;">Philips</td>
			<td style="width:187px;">B01YgG</td>
			<td>4-12 MHz phase array transducer</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;">Ultrasound Transmision Gel (Aquasone)</td>
			<td style="width:135px;">Parker laboratories Inc.</td>
			<td style="width:187px;">N 01-08</td>
			<td></td>
		</tr>
	</tbody>
</table>

transthoracic echocardiographic examination in the rabbit model

Large animal models such as the rabbit are valuable for translational preclinical research. Rabbits have a similar cardiac electrophysiology compared to that of humans and that of other large animal models such as dogs and pigs. However, the rabbit model has the additional advantage of lower maintenance costs compared to other large animal models. The longitudinal evaluation of cardiac function using echocardiography, when appropriately implemented, is a useful methodology for preclinical assessment of novel therapies for heart failure with reduced ejection fraction (e.g. cardiac regeneration). The correct use of this non-invasive tool requires the implementation of a standardized examination protocol following international guidelines. Here we describe, step by step, a detailed protocol supervised by veterinary cardiologists for performing echocardiography in the rabbit model, and demonstrate how to correctly obtain the different echocardiographic views and imaging planes, as well as the different imaging modes available in a clinical echocardiography system routinely used in human and veterinary patients.

Parasternal long axis view of the heart
Figure 5A shows an imaging plane of the right PSLAX view where the 4 chambers of the heart are clearly distinguished. You can identify in this view the right ventricle (RV), tricuspid valve (TV), IVS, LV, FW, as well as the mitral valve (MV). When the apex is clearly visible on the left side of the image in this view and the LV is not foreshor...

Watch this Scientific Journal Video about Transthoracic Echocardiographic Examination in the Rabbit Model at JoVE.com

Transthoracic Echocardiographic Examination in the Rabbit Model

Here we describe, step by step, a detailed protocol for performing echocardiography in the rabbit model. We show how to correctly obtain the different echocardiographic views and imaging planes, as well as the different imaging modes available in a clinical echocardiography system routinely used in human and veterinary patients.

Large animal models such as the rabbit are valuable for translational preclinical research. Rabbits have a similar cardiac electrophysiology compared to ...

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