We thank Manon Laprise for training in echocardiography and Ann Chamberland for taking the photos shown in Figures 1 and 2. This work was supported by Canadian Institutes of Health Research grant MOP 44363 and Canada Chair 950-216684.

All procedures shown in this protocol have been approved by the IRCM Animal Care Committee.
1. Ultrasound System and Station Preparation
<ol>
	<li>Start the ultrasound imaging system and connect the scanhead as well as the physiology controller unit according to the manufacturer&#39;s instruction (Figure 1). Choose Cardiac Measurement Program and the scanhead that corresponds to the 30 MHz transducer.</li>
	<li>Fill the nosepiece of the scanhead with deionized water. Avoid air bubbles as they interfere with imaging resolution. Place the scanhead with the handle side up on its holder near the imaging platform (Figure 1A).</li>
	<li>Disinfect the imaging platform and working area.</li>
	<li>Fill completely the bottle of ultrasound gel to avoid the formation of bubbles and place it upside down in its prewarming container set to 37 &#176;C (Figure 1B).</li>
	<li>Verify the levels of oxygen and isoflurane and the tubing system for anesthesia. One experiment with ~8 embryos would use approximately 15-20 L oxygen.</li>
	<li>Place the bottles of ophthalmic balm, depilatory cream and electrode gel near the imaging platform (Figure 1B).</li>
	<li>Verify that the infrared heat lamp functions. During training, set the heat level, the position of the lamp and the distance of the lamp to mice in order to maintain constant body temperature and heart rate. 
	Note: Proper preparation of the system and material is critical. Lengthy procedures may affect the physiologic and hemodynamic characteristics of fetuses as long anesthesia depresses cardiac function by lowering heart rate, blood pressure and blood-oxygenation level. The processing time for ~8 fetuses (average litter size in C57BL/6) should be approximately 1 hr. Other mouse strains may provide a higher number of fetuses, possibly with a larger female size. Training is essential to optimize the processing time.</li>
</ol>
2. Mouse Preparation
<ol>
	<li>Anesthetize the pregnant female in a chamber with continuous supply of 2% isoflurane in oxygen (200 ml/min) until it becomes nonresponsive.</li>
	<li>Place the mouse on the imaging platform in a supine position, adjust the tubing for continuous inhalation of 1.5% isoflurane in oxygen (200 ml/min), and fix the inhalation tube with tape (Figure 2A). Sufficient anesthesia should be confirmed during the procedure by the relaxed posture of the mouse and the absence of any response to tail and toe pinches.</li>
	<li>Place electrode gel only on the left top and right bottom electrode pads (right fore leg and left hind leg, also called lead II position) for electrocardiography. Lead II position provides better defined upright positive P-wave and QRS complex to determine heart rate. Secure the four paws to each pad using tape (Figure 2A). To prevent dryness of the eyes, apply 1 drop of ophthalmic balm into each eye.</li>
	<li>Shave the abdomen from chest to bladder with a hair clipper. Then apply depilatory cream for 2 min and wipe it off with gauze and/or cotton swab to carefully remove any remaining hair. Be careful not to cut the nipples.</li>
	<li>Insert the thermometer prelubricated with electrode gel into the female&#39;s rectum to monitor the body temperature (should be maintained at 37&#177;0.5 &#176;C by adjusting an infrared heat lamp placed above the platform). Heart rate should be 450&#177;50 beats/min (bpm). Both temperature and heart rate are displayed on the physiology controller unit (Figure 1B). 
	Note: Long anesthetization, hair loss and ultrasonic gel (although prewarmed) can lead to hypothermia, which can affect the female&#39;s heart rate. If the body temperature drops below 36.5 &#176;C, stop the procedure and modify the position of the heating lamp to adjust the temperature and the heart rate. Wait a couple of minutes before proceeding again.</li>
</ol>
3. Embryo Identification
<ol>
	<li>Gently press down on the naked abdomen to locate the embryos. Slowly and lightly spread them out to have most of embryos in a single layer under the abdominal surface. In each uterine horn, sacs are linearly connected to each other. Try to respect this order when spreading.</li>
	<li>Mark each embryo on the naked abdomen of the female with a permanent marker with their anterior/posterior and dorsal/ventral directions. Knowing the orientation will facilitate locating the heart with the probe. Number the embryos in the right and left horns starting from the cervix (1, 2, 3&#8230; and 1&#39;, 2&#39;, 3&#39;&#8230; respectively; Figure 2B). 
	Note: (i) Avoid spreading the embryos with excessive force. Sketch their locations on a piece of paper to track them (Figure 2C). (ii) C57BL/6 females have ~8 fetuses per litter. However, 0-2 embryos in each litter are located beneath the others, making their imaging impossible. Exclude these embryos from the analysis and assess more litters if needed.</li>
</ol>
4. Heart Rate Measurement
<ol>
	<li>Place a small amount of prewarmed ultrasound gel on the naked abdomen and spread it evenly. Avoid bubble formation. Add a larger amount of gel (~ 5 ml) on the specific area to image.</li>
	<li>Hold the probe in contact with the thick gel layer (10 mm) and gradually move the probe toward the skin while looking for the beating heart. Once the beating heart is visualized on the screen, adjust the angle of the probe to have both ventricles in their largest size in the imaging plane (Figure 2D).</li>
	<li>Begin acquiring image. With the forearm resting on the station, place the transducer on the ultrasound gel to obtain a live image on the viewing screen (Figure 2D). Maintaining the ridge of the transducer on the top and clicking the scanhead orientation marker (in the left top corner of the image) allow the coordination of the hand movement and area visualized on the screen.</li>
	<li>Starting from the cervix, move to the closest embryo marked (1 or 1&#39; in right or left uterine horn, respectively) to visualize the beating heart on the screen. Because focal depth is fixed, gently move the probe up/down and sideways without losing contact with gel to obtain the desired image plane.</li>
	<li>Position the beating heart in the center of the screen within the region indicated by the yellow dashed line representing the focal zone for better data acquisition.</li>
	<li>Acquire the live recording. Obtain the scout image and resume recording (Figure 3A). Once a minimum of 10 sec of stable recording is obtained, stop recording and save.</li>
	<li>Proceed to the next embryo.</li>
	<li>Once all the embryos are analyzed, press &#34;Browse&#34; on the keyboard to view the list of the recordings. Play each recorded M-mode tracing and perform multiple measurements (at least 5 per tracing) of the spacing between adjacent peaks (time/flow cycle) to obtain the average heart rate (Figure 3B). 
	Note: Some protocols suggest using a stationary stand for the scanhead to avoid shaking. However, it restrains the angle of analysis, making the observation of lateral embryos difficult. It also slows down the analysis, as the stand has to be adjusted for each embryo. Holding the scanhead while settling the forearm on the station efficiently minimizes shaking. Training with 5-10 pregnant females is recommended to optimize the outcome.</li>
</ol>
5. Genotyping
<ol>
	<li>Using clean surgical scissors and forceps, incise longitudinally the skin and muscle layer of the abdomen. Locate the sacs in each uterus horn and match the numbers. Cut open the yolk sac to expose the embryo in the order used above. If not in a linear arrangement, the sketch of the embryo positions on a piece of paper will be essential once the marks on the skin are no longer visible.</li>
	<li>Cut only ~4 mm of tail for genotyping as genomic DNA is very efficiently extracted from embryonic tails. 
	Note: (i) The surgical procedure may have to be performed in a separate location from the imaging room. However, it is important not to move the mouse and have the surgical procedure on the imaging platform in order to keep track of the numbered embryos. Consult the animal facility manager to optimize the surgical procedure. (ii) The pregnant female rapidly dies due to blood loss as the fetuses are removed for genotyping after imaging. After tail cut, the fetuses are placed 3 min on ice for anesthesia by hypothermia and then decapitated with scissors, as recommended by our Animal Care Committee.</li>
</ol>

<ol>
	<li>Hoffman, J. I., Kaplan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+incidence+of+congenital+heart+disease.">The incidence of congenital heart disease.</a> J. Am. Coll. Cardiol. 39, 1890-1900 (2002).</li><li>Miller, S. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abnormal+brain+development+in+newborns+with+congenital+heart+disease.">Abnormal brain development in newborns with congenital heart disease.</a> N. Engl. J. Med. 357, 1928-1938 (2007).</li><li>Bruneau, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+developmental+genetics+of+congenital+heart+disease.">The developmental genetics of congenital heart disease.</a> Nature. 451, 943-948 (2008).</li><li>Wessels, A., Sedmera, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developmental+anatomy+of+the+heart:+a+tale+of+mice+and.">Developmental anatomy of the heart: a tale of mice and.</a> 15, 165-176 (2003).</li><li>Yu, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ENU+induced+mutations+causing+congenital+cardiovascular+anomalies.">ENU induced mutations causing congenital cardiovascular anomalies.</a> Development. 131, 6211-6223 (2004).</li><li>Seidah, N. G., Prat, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biology+and+therapeutic+targeting+of+the+proprotein+convertases.">The biology and therapeutic targeting of the proprotein convertases.</a> Nat. Rev. Drug Discov. 11, 367-383 (2012).</li><li>Roebroek, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failure+of+ventral+closure+and+axial+rotation+in+embryos+lacking+the+proprotein+convertase+Furin.">Failure of ventral closure and axial rotation in embryos lacking the proprotein convertase Furin.</a> Development. 125, 4863-4876 (1998).</li><li>Roebroek, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Limited+redundancy+of+the+proprotein+convertase+furin+in+mouse+liver.">Limited redundancy of the proprotein convertase furin in mouse liver.</a> J. Biol. Chem. 279, 53442-53450 (2004).</li><li>Kisanuki, Y. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tie2-Cre+transgenic+mice:+a+new+model+for+endothelial+cell-lineage+analysis+in+vivo.">Tie2-Cre transgenic mice: a new model for endothelial cell-lineage analysis in vivo.</a> Dev. Biol. 230, 230-242 (2001).</li><li>Kim, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+endothelial+furin+leads+to+cardiac+malformation+and+early+postnatal+death.">Loss of endothelial furin leads to cardiac malformation and early postnatal death.</a> Mol. Cell Biol. 32, 3382-3391 (2012).</li></ol>

No conflict of interest declared.

M-mode echocardiography is an effective and simple method to measure in utero heart rates of mouse embryos. Commercially available transducers provide sufficient resolution to visualize small beating hearts. Thus, they allow a highly accurate heart rate measurement, as compared to other methods such as pulse measurement, and can substitute high resolution video microscopy. However, current tools do not allow the simultaneous analysis of all embryos, implying a tedious procedure to visualize each of the embryos. ...

CHD is the most common noninfectious cause of death at birth1. Multiple surgeries are often needed to correct the structural defects in subjects whose quality of life may remain compromised1. Children with CHD frequently develop neurological disorders even if they have not undergone surgery, indicating important in utero consequences on development2,3. Both genetic and environmental factors, such as exposure to viruses or chemicals (alcohol) during pregnancy, cause CHD. Studying the genetic contributors is still at its early phase, but growing rapidly. To identify these contributors and understand their role in heart development, phenotyping mutant mice with a simple and powerful tool will be highly beneficial.
Mouse is indeed an animal model of choice to study CHD, and most of the human cases can be reproduced in mice4,5. Consequently, fetal mouse cardiac phenotyping has become increasingly important to investigate the etiology of human CHD and requires adequate tools. Although histological studies on fixed specimens are invaluable, real-time imaging of live animals is crucial to understand the physiology of the heart. Video microscopy offers live imaging. However, it requires laparotomy to expose embryos, thereby compromising their physiologic and hemodynamic state. Recently, echocardiography has become the standard imaging technique for cardiac assessments in the clinic as well as in mice.
Mouse fetal echocardiography is conducted using standard clinical ultrasound systems as well as ultra-high frequency ultrasound systems. The latter provide 30 MHz or higher frequency transducers that generate two-dimensional images and allow the assessment of early embryonic stages. These transducers have a relatively poor penetration depth (~13 mm), which is, however, sufficient to obtain adequate imaging planes and determine fundamental heart parameters, such as heart rate, left and right ventricular internal diameter at diastole and systole and septum and wall thickness, without performing laparotomy.
In our study, we have used an ultra-high frequency ultrasound system to assess heart rates of mouse embryos at embryonic day E18.5. We chose a 30 MHz transducer that provides a field view of 20 mm x 20 mm, which is ideal given the size of the fetuses, with a focal length of 12.7 mm. However, a higher frequency transducer may be chosen to analyze earlier developmental stages. The selected M-mode allows the visualization of tissues in motion thanks to a high temporal resolution of 1,000 frames/sec. The full procedure is simple and should be performed as quickly as possible to avoid any perturbation of the physiologic and hemodynamic states of the fetus. The analysis of about 8 embryos requires approximately 1 hr.

<table><tbody><tr><td>Isoflurane</td><td>Pharmaceutical Partners of Canada Inc.</td><td>CP0406v2</td><td>1-chloro-2,2,2-trifluoroethyl difluoromethyl ether</td></tr><tr><td>Ultrasound gel</td><td>Parker Laboratories Inc.</td><td>Aquasonic Clear</td><td></td></tr><tr><td>Electrode gel</td><td>Parker Laboratories Inc.</td><td>Spectra 360</td><td></td></tr><tr><td>Ophthalmic gel</td><td>Novartis</td><td>Tear-Gel</td><td></td></tr><tr><td>Depilatory cream</td><td>Church Dwight Co., Inc.</td><td>Nair</td><td></td></tr><tr><td>Hair clipper</td><td></td><td></td><td></td></tr><tr><td>Gauze/cotton swap</td><td>Q-tips</td><td></td><td></td></tr><tr><td>Permanent marker</td><td></td><td></td><td></td></tr><tr><td>High-Resolution &lt;em&gt;In vivo&lt;/em&gt; Ultrasound Imaging System</td><td>Visual Sonics</td><td>Vevo770</td><td></td></tr><tr><td>30 MHz Transducer</td><td>Visual Sonics</td><td>RMV707B</td><td></td></tr><tr><td>Imaging platform and physiology controller unit</td><td>Visual Sonics</td><td></td><td></td></tr><tr><td>Anesthetic System</td><td>Cyprane North America Inc.</td><td>312462</td><td></td></tr><tr><td>Infrared heating lamp</td><td></td><td></td><td></td></tr></tbody></table>

in utero measurement of heart rate in mouse by noninvasive m-mode echocardiography

Congenital heart disease (CHD) is the most frequent noninfectious cause of death at birth. The incidence of CHD ranges from 4 to 50/1,000 births (Disease and injury regional estimates, World Health Organization, 2004). Surgeries that often compromise the quality of life are required to correct heart defects, reminding us of the importance of finding the causes of CHD. Mutant mouse models and live imaging technology have become essential tools to study the etiology of this disease. Although advanced methods allow live imaging of abnormal hearts in embryos, the physiological and hemodynamic states of the latter are often compromised due to surgical and/or lengthy procedures. Noninvasive ultrasound imaging, however, can be used without surgically exposing the embryos, thereby maintaining their physiology. Herein, we use simple M-mode ultrasound to assess heart rates of embryos at E18.5 in utero. The detection of abnormal heart rates is indeed a good indicator of dysfunction of the heart and thus constitutes a first step in the identification of developmental defects that may lead to heart failure.

The above method was used to assess the impact of the presence or absence of the serine protease furin in endothelial cells on heart rates of mouse embryos at E18.5 in utero. Furin belongs to the family of proprotein convertases (PCs) that cleave protein precursors after basic residues. Furin and its substrates are secretory proteins and cleavage can occur in the Golgi apparatus, endosomes or at the cell surface. Key substrates of furin include TGFb, and TGFb-like factors, such as the bone morphogenetic proteins...

Watch this Scientific Journal Video about In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography at JoVE.com

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Ultra-high frequency ultrasound is a powerful live imaging tool to examine cardiac abnormalities in small animals. Its noninvasiveness allows maintaining the physiologic state of embryos. Herein, we show the use of M-mode ultrasound to measure the heart rates of embryos at E18.5 in utero.

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Congenital heart disease (CHD) is the most frequent noninfectious cause of death at birth. The incidence of CHD ranges from 4 to 50/1,000 births (Disease ...

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11.3K Views.  Institut de Recherches Cliniques de Montréal. Ultra-high frequency ultrasound is a powerful live imaging tool to examine cardiac abnormalities in small animals. Its noninvasiveness allows maintaining the physiologic state of embryos. Herein, we show the use of M-mode ultrasound to measure the heart rates of embryos at E18.5 in utero.

Video: In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Transthoracic Echocardiography in Mice

In recent years, murine models have become the primary avenue for studying the molecular mechanisms of cardiac dysfunction resulting from changes in gene expression. Transgenic and gene targeting methods can be used to generate mice with altered cardiac size and function,1-3 and as a result, in vivo techniques are needed to evaluate their cardiac phenotype. Transthoracic echocardiography, pulse wave Doppler (PWD), and tissue Doppler imaging (TDI) can be used to provide dimensional measurements of the mouse heart and to quantify the degree of cardiac systolic and diastolic performance. Two-dimensional imaging is used to detect abnormal anatomy or movements of the left ventricle, whereas M-mode echo is used for quantification of cardiac dimensions and contractility.4,5 In addition, PWD is used to quantify localized velocity of turbulent flow,6 whereas TDI is used to measure the velocity of myocardial motion.7 Thus, transthoracic echocardiography offers a comprehensive method for the noninvasive evaluation of cardiac function in mice.

Transthoracic echocardiography offers a noninvasive method for the evaluation of cardiac function in mice. A combination of ultrasound and Doppler imaging modalities can be used to obtain dimensional measurements of the heart and intracardiac blood flow, which together provide an assessment of cardiac systolic and diastolic performance.

In recent years, murine models have become the primary avenue for studying the molecular mechanisms of cardiac dysfunction resulting from changes in gene ...

High-frequency High-resolution Echocardiography: First Evidence on Non-invasive Repeated Measure of Myocardial Strain, Contractility, and Mitral Regurgitation in the Ischemia-reperfused Murine Heart

Ischemia-reperfusion (IR) was surgically performed in murine hearts which were then subjected to repeated imaging to monitor temporal changes in functional parameters of key clinical significance. Two-dimensional movies were acquired at high frame rate (8 kHz) and were utilized to estimate high-quality myocardial strain. Two-dimensional elastograms (strain images), as well as strain profiles, were visualized. Results were powerful in quantitatively assessing IR-induced changes in cardiac events including left-ventricular (LV) contraction, LV relaxation and isovolumetric phases of both pre-IR and post-IR beating hearts in intact mice. In addition, compromised sector-wise wall motion and anatomical deformation in the infarcted myocardium were visualized.  The elastograms were uniquely able to provide information on the following parameters in addition to standard physiological indices that are known to be affected by myocardial infarction in the mouse: internal diameters of mitral valve orifice and aorta, effective regurgitant orifice, myocardial strain (circumferential as well as radial), turbulence in blood flow pattern as revealed by the color Doppler movies and velocity profiles, asynchrony in LV sector, and changes in the length and direction of vectors demonstrating slower and asymmetrical wall movement. This work emphasizes on the visual demonstration of how such analyses are performed. 

High-frequency High-resolution Echocardiography: First Evidence on Non-invasive Repeated Measure of Myocardial Strain, Contractility, and Mitral Regurgitation in the Ischemia-reperfused Murine Heart 

High frequency Doppler ultrasound is a novel technology for assessing regional myocardial function. This work presents first evidence demonstrating applicability of this versatile imaging platform for the repeated measure of myocardial strain, dp/dt, and mitral regurgitation in the ischemia-reperfused (IR) murine heart.

Ischemia-reperfusion (IR) was surgically performed in murine hearts which were then subjected to repeated imaging to monitor temporal changes in ...

Murine Echocardiography and Ultrasound Imaging

Rodent models of cardiac pathophysiology represent a valuable research tool to investigate mechanism of disease as well as test new therapeutics.1 Echocardiography provides a powerful, non-invasive tool to serially assess cardiac morphometry and function in a living animal.2 However, using this technique on mice poses unique challenges owing to the small size and rapid heart rate of these animals.3 Until recently, few ultrasound systems were capable of performing quality echocardiography on mice, and those generally lacked the image resolution and frame rate necessary to obtain truly quantitative measurements. Newly released systems such as the VisualSonics Vevo2100 provide new tools for researchers to carefully and non-invasively investigate cardiac function in mice. This system generates high resolution images and provides analysis capabilities similar to those used with human patients. Although color Doppler has been available for over 30 years in humans, this valuable technology has only recently been possible in rodent ultrasound.4,5 Color Doppler has broad applications for echocardiography, including the ability to quickly assess flow directionality in vessels and through valves, and to rapidly identify valve regurgitation. Strain analysis is a critical advance that is utilized to quantitatively measure regional myocardial function.6 This technique has the potential to detect changes in pathology, or resolution of pathology, earlier than conventional techniques. Coupled with the addition of three-dimensional image reconstruction, volumetric assessment of whole-organs is possible, including visualization and assessment of cardiac and vascular structures. Murine-compatible contrast imaging can also allow for volumetric measurements and tissue perfusion assessment.

This video demonstrates use of a rail-mounted high-frequency ultrasound probe to perform echocardiography on an anesthetized mouse. The methods describe both conventional two-dimensional and M-mode measurements of cardiac function in addition to newer, more powerful tools such as color Doppler, strain analysis, as well as general and targeted contrast imaging.

Rodent models of cardiac pathophysiology represent a valuable research tool to investigate mechanism of disease as well as test new therapeutics.1  ...

Murine Fetal Echocardiography

Transgenic mice displaying abnormalities in cardiac development and function represent a powerful tool for the understanding the molecular mechanisms underlying both normal cardiovascular function and the pathophysiological basis of human cardiovascular disease. Fetal and perinatal death is a common feature when studying genetic alterations affecting cardiac development 1-3. In order to study the role of genetic or pharmacologic alterations in the early development of cardiac function, ultrasound imaging of the live fetus has become an important tool for early recognition of abnormalities and longitudinal follow-up. Noninvasive ultrasound imaging is an ideal method for detecting and studying congenital malformations and the impact on cardiac function prior to death 4. It allows early recognition of abnormalities in the living fetus and the progression of disease can be followed in utero with longitudinal studies 5,6. Until recently, imaging of fetal mouse hearts frequently involved invasive methods. The fetus had to be sacrificed to perform magnetic resonance microscopy and electron microscopy or surgically delivered for transillumination microscopy. An application of high-frequency probes with conventional 2-D and pulsed-wave Doppler imaging has been shown to provide measurements of cardiac contraction and heart rates during embryonic development with databases of normal developmental changes now available 6-10. M-mode imaging further provides important functional data, although, the proper imaging planes are often difficult to obtain. High-frequency ultrasound imaging of the fetus has improved 2-D resolution and can provide excellent information on the early development of cardiac structures 11.

Fetal and perinatal death is a common feature when studying genetic alterations affecting cardiac development. High-frequency ultrasound imaging has improved 2-D resolution and can provide excellent information on early cardiac development and is an ideal method to detect the impact on cardiac structure and function prior to death.

Transgenic mice displaying abnormalities in  cardiac development and function represent a powerful tool for the understanding  the molecular mechanisms ...

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound (30/45MHZ) System

Congenital heart defects (CHDs) are the most common cause of childhood morbidity and early mortality. Prenatal detection&#160;of the underlying molecular mechanisms of CHDs is&#160;crucial for inventing new preventive and therapeutic strategies. Mutant mouse models are powerful tools to discover new&#160;mechanisms&#160;and environmental stress modifiers that drive cardiac development and their potential&#160;alteration in CHDs. However, efforts to establish the causality of these putative contributors have been limited to histological&#160;and molecular studies&#160;in non-survival animal experiments, in which&#160;monitoring the key physiological and hemodynamic parameters is&#160;often absent. Live imaging technology has become an essential tool to establish the&#160;etiology of CHDs. In particular,&#160;ultrasound imaging can be used prenatally without surgically exposing the fetuses,&#160;allowing maintaining&#160;their baseline physiology while monitoring the impact of environmental stress&#160;on the hemodynamic and structural aspects of cardiac chamber development. Herein, we use the High-Frequency Ultrasound (30/45)&#160;system to examine the cardiovascular system in fetal mice at E18.5 in utero at the baseline and in response to prenatal hypoxia exposure. We demonstrate the feasibility of the system to measure cardiac chamber size, morphology, ventricular function, fetal heart rate, and umbilical artery flow indices, and their alterations in fetal mice exposed to systemic chronic hypoxia in utero in real time.

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound 30/45MHZ System

High-frequency ultrasound imaging of the fetal mouse has improved imaging resolution and can provide precise non-invasive characterization of cardiac development and structural defects. The protocol outlined herein is designed to perform real-time fetal mice echocardiography in vivo.

Congenital heart defects (CHDs) are the most common cause of childhood morbidity and early mortality. Prenatal detection&#160;of the underlying molecular ...

Developmental Biology

Echocardiographic Approaches and Protocols for Comprehensive Phenotypic Characterization of Valvular Heart Disease in Mice

The aim of this manuscript and accompanying video is to provide an overview of the methods and approaches used for imaging heart valve function in rodents, with detailed descriptions of the appropriate methods for anesthesia, the echocardiographic windows used, the imaging planes and probe orientations for image acquisition, the methods for data analysis, and the limitations of emerging technologies for the evaluation of cardiac and valvular function. Importantly, we also highlight several future areas of research in cardiac and heart valve imaging that may be leveraged to gain insights into the pathogenesis of valve disease in preclinical animal models. We propose that using a systematic approach to evaluating cardiac and heart valve function in mice can result in more robust and reproducible data, as well as facilitate the discovery of previously underappreciated phenotypes in genetically-altered and/or physiologically-stressed mice.

This protocol provides a detailed description of the echocardiographic approach for comprehensive phenotyping of heart and heart valve function in mice.

The aim of this manuscript and accompanying video is to provide an overview of the methods and approaches used for imaging heart valve function in ...

Murine Echocardiography of Left Atrium, Aorta, and Pulmonary Artery

The present methodology teaches the investigator how to measure and use the LAV as a surrogate of chronic elevations in Left Ventricular diastolic pressure through echocardiography, as well as to obtain measurements of the Aorta and PA diameter in mice.
Mice older than 10 d of age can be analyzed using the present technique. The technique is composed of 3 main steps: set-up, image acquisition, and image analysis. The set-up step consists of getting the mouse anesthetized with 1% isoflurane, shaving it, and taping it in a supine position to a heated EKG board where the image acquisition will take place. The image acquisition step consists of learning to identify the cardiac structures and obtaining all the required images with its correspondent probe and axis in order to be able to calculate volumes and diameters. The image analysis step consists of measuring the previously acquired images with the aid of computer software.
Advantages of the proposed technique include a fast (15 min) procedure that would allow the researcher to evaluate interventions in a non-invasive, non-terminal approach and therefore follow the same mouse over time; each mouse can be used as its own control. This fact plus having the same operator perform all the acquisition and analysis for the entire experiment minimizes the limitation of operator-dependency. The present methodology is useful for mouse researchers in cardiovascular and pulmonary medicine.

The following protocol describes the methodology for the acquisition and analysis of echocardiographic images used to obtain the Left Atrial Volume (LAV), Aorta (Ao) diameter, and Pulmonary Artery (PA) diameter in mice. This technique is a non-invasive, non-terminal procedure that allows assessment of the cardiopulmonary function.

The present methodology teaches the investigator how to measure and use the LAV as a surrogate of chronic elevations in Left Ventricular diastolic ...

Echocardiographic Measurement of Right Ventricular Diastolic Parameters in Mouse

Diastolic dysfunction is a prominent feature of right ventricular (RV) remodeling associated with conditions of pressure overload. However, the RV diastolic function is rarely quantified in experimental studies. This might be due to technical difficulties in the visualization of the RV in the apical four-chamber view in rodents. Here we describe two positions facilitating the visualization of the apical four-chamber view in mice to assess the RV diastolic function.
The apical four-chamber view is enabled by tilting the mouse fixation platform to the left and caudally (LeCa) or to the right and cranially (RiCr). Both positions provide images of comparable quality. The results of the RV diastolic function obtained from two positions are not significantly different. Both positions are comparably easy to perform. This protocol can be incorporated into published protocols and enables detailed investigations of the RV function.

Here we describe and compare two positions for obtaining the apical four-chamber view in mice. These positions enable the quantification of the right ventricular function, provide comparable results, and can be used interchangeably.

Diastolic dysfunction is a prominent feature of right ventricular (RV) remodeling associated with conditions of pressure overload. However, the RV ...

Noninvasive Electrocardiography in the Perinatal Mouse

Electrocardiography (ECG) has long been relied upon as an effective and reliable method of assessing cardiovascular (and cardiopulmonary) function in both human and animal models of disease. Individual heart rate, rhythm, and regularity, combined with quantitative parameters collected from ECG, serve to assess the integrity of the cardiac conduction system as well as the integrated physiology of the cardiac cycle. This article provides a comprehensive description of the methods and techniques used to perform a noninvasive ECG on perinatal and neonatal mouse pups as early as the first postnatal day, without requiring the use of anesthetics. This protocol was designed to directly address a need for a standardized and repeatable method for obtaining ECG in newborn mice. From a translational perspective, this protocol proves to be entirely effective for characterization of congenital cardiopulmonary defects generated using transgenic mouse lines, and particularly for analysis of defects causing lethality at or during the first postnatal days. This protocol also aims to directly address a gap in the scientific literature to characterize and provide normative data associated with maturation of the early postnatal cardiac conduction system. This method is not limited to a specific postnatal timepoint, but rather allows for ECG data collection in neonatal mouse pups from birth to postnatal day 10 (P10), a window that is of critical importance for modeling human diseases in vivo, with particular emphasis on congenital heart disease (CHD).

Here, we present a noninvasive electrocardiography (ECG) protocol, optimized for early postnatal mice, that does not require the use of anesthetics.

Electrocardiography (ECG) has long been relied upon as an effective and reliable method of assessing cardiovascular (and cardiopulmonary) function in both ...

Echocardiographic Characterization of Left Ventricular Structure, Function, and Coronary Flow in Neonate Mice

Echocardiography is a non-invasive procedure that enables the evaluation of structural and functional parameters in animal models of cardiovascular disease and is used to assess the impact of potential treatments in preclinical studies. Echocardiographic studies are usually conducted in young adult mice (i.e., 4-6 weeks of age). The evaluation of early neonatal cardiovascular function is not usually performed because of the small size of the mouse pups and the associated technical difficulties. One of the most important challenges is that the short length of the pups&#39; limbs prevents them from reaching the electrodes in the echocardiography platform. Body temperature is the other challenge, as pups are very susceptible to changes in temperature. Therefore, it is important to establish a practical guide for performing echocardiographic studies in small mouse pups to help researchers detect early pathological changes and study the progression of cardiovascular disease over time. The current work describes a protocol for performing echocardiography in mouse pups at the early age of 7 days old. The echocardiographic characterization of cardiac morphology, function, and coronary flow in neonatal mice is also described.

The present protocol describes the echocardiographic assessment of left ventricular morphology, function, and coronary blood flow in 7-day old neonate mice.

Echocardiography is a non-invasive procedure that enables the evaluation of structural and functional parameters in animal models of cardiovascular ...

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

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Chapters in this video

Transthoracic Echocardiography in Mice

High-frequency High-resolution Echocardiography: First Evidence on Non-invasive Repeated Measure of Myocardial Strain, Contractility, and Mitral Regurgitation in the Ischemia-reperfused Murine Heart

Murine Echocardiography and Ultrasound Imaging

Murine Fetal Echocardiography

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound (30/45MHZ) System

Echocardiographic Approaches and Protocols for Comprehensive Phenotypic Characterization of Valvular Heart Disease in Mice

Murine Echocardiography of Left Atrium, Aorta, and Pulmonary Artery

Echocardiographic Measurement of Right Ventricular Diastolic Parameters in Mouse

Noninvasive Electrocardiography in the Perinatal Mouse

Echocardiographic Characterization of Left Ventricular Structure, Function, and Coronary Flow in Neonate Mice