This work was supported by The Danish Council for Independent Research [11e108410], the Danish Heart Foundation [12e04-R90-A3852 and 12e04-R90-A3907], and The Novo Nordisk Foundation [NNF16OC0023244].

All rats were treated according to Danish national guidelines&#160;described in the Danish law on animal experiments and Ministerial order on animal experiments. All experiments were approved by the Institutional Ethics Review Board and conducted in accordance with the Danish law for animal research (authorization number 2012-15-2934-00384, Danish Ministry of Justice).
1. Adjustment of the Ligating Clip Applier
NOTE: The banding of the pulmonary trunk is performed with a modified open ligating clip applier with an angled jaw. The applier is modified with an adjustable stop mechanism to stop the compression when the jaws reach an exact distance from each other. When a small titanium ligating clip is compressed with the modified applier, a lumen persists between the legs of the clip with a specific diameter according to the adjustment of the stop mechanism (Figure 1).
<ol>
	<li>Choose the diameter of the desired banding, e.g., 0.6 mm.</li>
	<li>Adjust the ligating clip applier until the distance between the jaws is 1.0 mm when fully compressed. This leaves a lumen of 0.6 mm as the two clip legs have a thickness of 0.2 mm each.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58050/58050fig1.jpg" /> 
Figure 1: The PTB procedure.&#160;(A) The surgical instruments used for the PTB procedure including the ligating clip applier (blue arrow). (B) The adjustable stop mechanism of the ligating clip applier. Turning the cogwheel (blue arrow) will adjust the position of the pin (yellow arrow), which stops the closing of the applier when the jaws reach a certain distance from each other. The distance corresponds to twice the thickness of the legs of the clip plus the inner diameter of the clip, when the clip is compressed, and can be calibrated by using for example a needle with a known outer diameter. (C) The applier compresses a titanium clip to an exact inner diameter pre-specified by adjustment of the applier. (D) The inner diameter of the compressed clip can be adjusted in order to induce different severities of RV hypertrophy and failure. For the data presented, an inner diameter of 1.0 mm was used to induce mild RV hypertrophy, an inner diameter of 0.6 mm was used to induce moderate RV failure, and an inner diameter of 0.5 mm was used to induce severe RV failure. (E) The clip after application around the pulmonary trunk. <a href="https://www.jove.com/files/ftp_upload/58050/58050fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Preparation of the Rat
NOTE: Other regimens of analgesics may be applied.
<ol>
	<li>Use Wistar rat weanlings weighing approximately 100&#8211;120 g. In order to maintain body temperature during the surgery, use a covered heating pad.</li>
	<li>For surgery, use a mechanical ventilator set to a tidal volume of approximately 1.75 mL and respiratory rate of 75 per min.</li>
	<li>Anaesthetize the rat with sevoflurane (7% mix in 1.5 L of O2) in an induction chamber for 5 minutes. Intubate the rat using a 17 G IV cannula, where the distal 2 mm of the needle have been cut off in order for the soft catheter to cover the tip. Remove the needle and connect the cannula to the ventilator.</li>
	<li>Place the rat on its back on the heating pad. Make sure that the intubation is correct by observing the movements of the thorax. These should be without side differences and in pace with the ventilator. 
	NOTE: Absence of movements of the thorax, abdominal contractions and inflation of the stomach in the upper left abdomen are signs of a misplaced tube. Remove the cannula, put the rat back in the induction chamber and re-intubate.</li>
	<li>After correct intubation, reduce the sevoflurane to maintenance concentration (3.5% mix in O2, 1.5 L/min) and fix the paws of the rat to the heating pad.</li>
	<li>Confirm prober anesthetization by checking withdrawal reflexes of the extremities using a forceps to squeeze the paws of the rat.</li>
	<li>Inject the rats with buprenorphine (0.1 mg/kg subcutaneously (s.c.)) and carprofene (5 mg/kg s.c.) to relieve post-operative pain.</li>
	<li>Shave the chest and disinfect with chlorhexidine.</li>
</ol>
3. Isolation of the Pulmonary Trunk
<ol>
	<li>With a pair of scissors, make a 2 cm incision in the skin along the middle part of the sternum. Identify the major pectoral muscle and cut its sternal attachment. Identify the 2nd, 3rd, and 4th costa below.</li>
	<li>Optionally, grab the 2nd costa with a fixation forceps, put a suture (4-0, multifilament, absorbable) around the 2nd costa from the 1st intercostal space to the lower medial part of the 2nd intercostal space. Tie a firm knot in order to ligate the anterior thoracic artery. 
	NOTE:&#160;This can be useful if bleeding from the anterior thoracic artery is a recurrent issue.</li>
	<li>Cut the 4th, 3rd, and 2nd costa close to the sternum with a pair of scissors and carefully dissect the intercostal muscles until a complete left thoracotomy has been performed. If any bleeding from the anterior thoracic artery occurs, compress with a pean and ligate the artery.</li>
	<li>Insert a retractor between the sternum and the costae and open it to get a good operating field. At the top of the field is the thymus covering the aorta and the pulmonary trunk. Carefully lift the thymus using a pean and flip it upwards in order to expose the aorta and the pulmonary trunk below.</li>
	<li>Guide the tip of a small surgical hooklet with a 85&#176; angle through the transverse pericardial sinus located behind the left atrial appendage. Pull it halfway back through the sinus and guide the tip of the ear hook upwards until it appears between the ascending aorta and the pulmonary trunk.
	<ol>
		<li>Remove any connective tissue covering the tip with an iris scissor in order to separate the pulmonary trunk from the ascending aorta.</li>
		<li>Repeat the step with a larger hook (optional).</li>
	</ol>
	</li>
	<li>Guide an angled muscle forceps around the pulmonary trunk through the passage made with the hook(s). Grab the end of an approximately 10 cm ligature (4-0, multifilament) and pull half of the ligature back through the passage. Now the pulmonary trunk is separated from the ascending aorta and can be controlled by the ligature around it.</li>
</ol>
4. Application of the Clip
<ol>
	<li>Load the adjusted ligating clip applier with a clip. Carefully guide one of the jaws and one leg of the clip though the passage around the pulmonary trunk. Use the ligature to gently pull the pulmonary trunk upwards and into the fork of the clip.</li>
	<li>When the pulmonary trunk is in the fork of the clip and the two tips of the clip legs are free of any connective tissue, compress the clip with the applier to apply the banding.</li>
	<li>Observe how the RV immediately dilates in response to the banding and remove the ligature.</li>
</ol>
5. Closing of the Thorax
<ol>
	<li>Remove the pean from the thymus and reposition the thymus&#160;to its natural position. Remove the retractor.</li>
	<li>Close the thorax in three layers: the intercostal layer, the major pectoral muscle, and the skin with suture (4-0, multifilament, absorbable). Inject 2 mL of saline s.c. to replace fluid lost during surgery.</li>
	<li>Turn the sevoflurane off and and keep the rat on the ventilator (1.5 L of O2) until it starts breathing spontaneously. Then, extubate the rat.</li>
	<li>Treat the rats with buprenorphine in the drinking water for the following three days14 or apply a similar analgesic protocol. After three days, the rats have recovered and are without discomfort.</li>
	<li>In the following weeks, the well-being of the rats and possible adverse effects should be evaluated on a daily basis. The healing of the wound from the thoracotomy should receive special attention during the first week in order to detect any signs of infection or insufficiency of the cicatrices. If the rats show signs of failure to thrive including bristly fur, impaired mobility, respiratory problems, and weight loss, they should be monitored closely and euthanized if they lose more than 20% of their body weight or develop fulminant respiratory insufficiency.&#160;</li>
</ol>
6. Sham Surgery
<ol>
	<li>Perform a sham surgery by following all of the steps above except for the application of the clip (step 4).</li>
</ol>

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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Right+ventricular+myocardium+derives+from+the+anterior+heart+field.">Right ventricular myocardium derives from the anterior heart field.</a> Circulation Research. 95 (3), 261-268 (2004).</li><li>de Raaf, M. A., 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=SuHx+rat+model:+partly+reversible+pulmonary+hypertension+and+progressive+intima+obstruction.">SuHx rat model: partly reversible pulmonary hypertension and progressive intima obstruction.</a> The European Respiratory Journal. 44 (1), 160-168 (2014).</li><li>Gomez-Arroyo, J. 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The authors have nothing to disclose

We describe an accessible and highly reproducible method of pulmonary trunk banding using a modified ligating clip applier to compress a titanium clip around the pulmonary trunk. By adjusting the applier to compress the clip to different inner diameters, distinct phenotypes of RV hypertrophy and failure can be induced including severe RV failure with extra-cardiac manifestation of decompensation.
Although simple, the protocol contains a few critical steps. Importantly, the rats cannot be too b...

The right ventricle (RV) can adapt to a persistent pressure overload. In time, however, adaptive mechanisms fail to sustain cardiac output, the RV dilates and eventually the RV fails. RV function is the main prognostic factor of several cardiopulmonary disorders including pulmonary arterial hypertension (PAH), thromboembolic pulmonary hypertension (CTEPH), and various forms of congenital heart disease with a pressure (or volume) overload of the RV. Despite intense treatment, RV failure remains a predominant cause of death in these conditions.
As a consequence of the unique properties1,2 and embryological development3 of the RV, knowledge derived from left heart failure cannot simply be extrapolated to right heart failure. Animal models of right heart failure are therefore needed in order to investigate the mechanisms of RV failure and potential pharmacological treatment strategies.
There are experimental models of pulmonary hypertension induced by SU5416 combined with hypoxia (SuHx)4 or monocrotaline (MCT)5, which induce RV failure secondary to disease in the pulmonary vasculature. These models are used to evaluate therapeutic effects of drugs that target the pulmonary vasculature. Both the SuHx and the MCT model are non-fixed afterload models of RV failure. Consequently, it is not possible to conclude if an improvement in RV function after an intervention is secondary to afterload reducing pulmonary vascular effects or if it is caused by direct effects on the RV. In addition, the MCT model has several extra-cardiac effects.
In experimental pulmonary trunk banding models, the afterload of the RV is fixed due to a mechanical constriction of the pulmonary trunk. This allows for the investigation of direct cardiac effects of an intervention on the RV independent from any pulmonary vascular effects6,7,8,9. Usually, the banding is performed by placing a needle along the pulmonary trunk. Then a ligature is placed around the needle and the pulmonary trunk and tied with a knot, and the needle is removed leaving the suture around the pulmonary trunk. Depending on the gauge of the needle, different degrees of constrictions can be applied, but despite this approach being widely used, it has some disadvantages. First, the diameter of the banding is not exactly the same as the outer diameter of the needle as the ligature is tied around both the needle and the pulmonary trunk. Second, there may be significant variation to how tightly the knot is tied making it difficult to reproduce a certain degree of banding. This will lead to a variation in banding diameter and thereby a larger dispersion. Finally, the knot may come loose over time.
One study applies a half-closed tantalum clip around the pulmonary trunk10. They compressed the clip around the pulmonary trunk to an inner area of 1.10 mm2 and compared it to rats subjected to banding with a suture using an 18 G needle. Overall, banding with the clip was associated with less peri-surgical complications and data variance.
Based on the principles described by Schou et al.11, we further developed and characterized the pulmonary trunk banding (PTB) model of RV hypertrophy and failure. Here, we present our experience using this model based on results from previous studies12,13. For this model, a titanium clip is compressed around the pulmonary trunk to an exact preset inner diameter, which may be adjusted in order to induce distinct RV failure phenotypes.

<table border="0" cellpadding="0" cellspacing="0" width="804">
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:217px;">17G IV Venflon Cannula</td>
			<td style="width:189px;">Becton Dickinson, US</td>
			<td style="width:108px;">393228</td>
			<td style="width:291px;">Distal 2 mm of the needle have been cut off</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">1 mL syringe + 26G needle&#160;</td>
			<td>Becton Dickinson, US</td>
			<td>303172 &#38; 303800</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">4-0 absorbable multifilament suture</td>
			<td>Covidien, US</td>
			<td>GL-46-MG</td>
			<td>Polysorb, violet, 5x18&#34;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">4-0 multifilament ligature</td>
			<td>Covidien, US</td>
			<td>LL-221</td>
			<td>Polysorb, violet, 98&#34;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Buprenorphine</td>
			<td>Indivior UK Limited</td>
			<td></td>
			<td>Local procurement, Temgesic 0.3 mg/mL</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Carprofene</td>
			<td>ScanVet, DK</td>
			<td>27693</td>
			<td>Norodyl 50 mg/mL</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Chlorhexidine</td>
			<td>Faaborg Pharma, DK</td>
			<td></td>
			<td>Local procurement</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Contractor</td>
			<td>Aesculap, Germany</td>
			<td>BV010R</td>
			<td>Blunt, self retaining, 70 mm</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Ear Hooklet</td>
			<td>Lawton, Germany</td>
			<td>66-0261</td>
			<td>Small, 14 cm, tip modified to an angle of 85&#176;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Eye gel</td>
			<td>Decra, UK</td>
			<td></td>
			<td>Lubrithal, Local procurement</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Forceps, Delicate Tissue&#160;</td>
			<td>Lawton, Germany</td>
			<td>09-0020</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Forceps, Dissecting&#160;</td>
			<td>Lawton, Germany</td>
			<td>09-0013</td>
			<td>1 regular, 1 with tip modified to an angle of 100&#176;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Gas Anesthesia System</td>
			<td>Penlon Limited, UK</td>
			<td>SD0217SL</td>
			<td>Sigma Delta Vaporizer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Hair trimmer</td>
			<td>Oster</td>
			<td>76998-320-051</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Horizon Open Ligating Clip Applier</td>
			<td>Teleflex, US</td>
			<td>137085</td>
			<td>Modified with adjustable stop mechanism</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Horizon Titanium Clips</td>
			<td>Teleflex, US</td>
			<td>001200</td>
			<td>Small</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Induction chamber</td>
			<td>N/A</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Iris Scissor</td>
			<td>Lawton, Germany</td>
			<td>05-1450</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Iris Scissor&#160;</td>
			<td>Aesculap, Germany</td>
			<td>BC060R</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Mechanical ventilator</td>
			<td>Ugo Basile, Italy</td>
			<td>7025</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Microscissor</td>
			<td>Lawton, Germany</td>
			<td>63-1406</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Microscope</td>
			<td>Carl Zeiss, Germany</td>
			<td>303294-9903</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Needle Holder</td>
			<td>Lawton, Germany</td>
			<td>08-0011</td>
			<td>&#160;TITEGRIP</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Pean</td>
			<td>Lawton, Germany</td>
			<td>06-0100</td>
			<td>Halsted-Mosquito, straight</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Pro-Optha</td>
			<td>Lohmann &#38; Rauscher, Germany</td>
			<td>16515</td>
			<td>Tampon</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Saline 9 mg/mL</td>
			<td>Fresenius Kabi, DK</td>
			<td>209319</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Sevoflurane</td>
			<td>AbbVie, US</td>
			<td></td>
			<td>Sevorane, Local procurement</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Surgical hook</td>
			<td>Lawton, Germany</td>
			<td>51-0665</td>
			<td>Cushing, 19 cm, tip modified to an angle of 90&#176;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Surgical Tape</td>
			<td>3M, US</td>
			<td>1530-0</td>
			<td>Micropore</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Temperature Controller</td>
			<td>CMA Microdialysis; Sweden</td>
			<td>8003760</td>
			<td>CMA 450&#160;</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Weighing machine</td>
			<td>VWR, US</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:217px;">Wistar rat weanlings</td>
			<td>Janvier Labs, France</td>
			<td style="width:108px;"></td>
			<td>RjHan:WI, 100-120 g</td>
		</tr>
	</tbody>
</table>

a pulmonary trunk banding model of pressure overload induced right ventricular hypertrophy and failure

Right ventricular (RV) failure induced by sustained pressure overload is a major contributor to morbidity and mortality in several cardiopulmonary disorders. Reliable and reproducible animal models of RV failure are therefore warranted in order to investigate disease mechanisms and effects of potential therapeutic strategies. Banding of the pulmonary trunk is a common method to induce isolated RV hypertrophy but in general, previously described models have not succeeded in creating a stable model of RV hypertrophy and failure.
We present a rat model of pressure overload induced RV hypertrophy caused by pulmonary trunk banding (PTB) that enables different phenotypes of RV hypertrophy with and without RV failure. We use a modified ligating clip applier to compress a titanium clip around the pulmonary trunk to a pre-set inner diameter. We use different clip diameters to induce different stages of disease progression from mild RV hypertrophy to decompensated RV failure.
RV hypertrophy develops consistently in rats subjected to the PTB procedure and depending on the diameter of the applied banding clip, we can accurately reproduce different disease severities ranging from compensated hypertrophy to severe decompensated RV failure with extra-cardiac manifestations.
The presented PTB model is a valid and robust model of pressure overload induced RV hypertrophy and failure that has several advantages to other banding models including high reproducibility and the possibility of inducing severe and decompensated RV failure.

Using the described PTB procedure in previous studies from our group12,13, we induced RV hypertrophy (PTB mild) by banding with a 1.0 mm clip, a moderate degree of RV failure (PTB moderate) by banding with a 0.6 mm clip and a severe degree of RV failure (PTB severe) by banding with a 0.5 mm clip. The rats subjected to the severe banding developed extra-cardiac manifestations of RV failure including liver failure and ascites (<stro...

Watch this Scientific Journal Video about A Pulmonary Trunk Banding Model of Pressure Overload Induced Right Ventricular Hypertrophy and Failure at JoVE.com

A Pulmonary Trunk Banding Model of Pressure Overload Induced Right Ventricular Hypertrophy and Failure

We present a surgical method to induce right ventricular hypertrophy and failure in rats.

Right ventricular (RV) failure induced by sustained pressure overload is a major contributor to morbidity and mortality in several cardiopulmonary ...

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9.5K Views.  Aarhus University Hospital. We present a surgical method to induce right ventricular hypertrophy and failure in rats.

Video: A Pulmonary Trunk Banding Model of Pressure Overload Induced Right Ventricular Hypertrophy and Failure

Ascending Aortic Constriction in Rats for Creation of Pressure Overload Cardiac Hypertrophy Model

Ascending aortic constriction is the most common and successful surgical model for creating pressure overload induced cardiac hypertrophy and heart failure. Here, we describe a detailed surgical procedure for creating pressure overload and cardiac hypertrophy in rats by constriction of the ascending aorta using a small metallic clip. After anesthesia, the trachea is intubated by inserting a cannula through a half way incision made between two cartilage rings of trachea. Then a skin incision is made at the level of the second intercostal space on the left chest wall and muscle layers are cleared to locate the ascending portion of aorta. The ascending aorta is constricted to 50&#8211;60% of its original diameter by application of a small sized titanium clip. Following aortic constriction, the second and third ribs are approximated with prolene sutures. The tracheal cannula is removed once spontaneous breathing was re-established. The animal is allowed to recover on the heating pad by gradually lowering anesthesia. The intensity of pressure overload created by constriction of the ascending aorta is determined by recording the pressure gradient using trans-thoracic two dimensional Doppler-echocardiography. Overall this protocol is useful to study the remodeling events and contractile properties of the heart during the gradual onset and progression from compensated cardiac hypertrophy to heart failure stage.

We describe a stepwise procedure for creating pressure overload and left ventricular hypertrophy in Wistar rats by constriction of the ascending aorta using a small metallic clip. This model is extensively used for studying remodeling changes during cardiac hypertrophy and for identifying and evaluating strategies for regression of such changes.

Ascending aortic constriction is the most common and successful surgical model for creating pressure overload induced cardiac hypertrophy and heart ...

Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, the RV is significantly affected in pulmonary diseases such as pulmonary artery hypertension (PAH). In addition, the RV is remarkably sensitive to cardiac pathologies, including left ventricular (LV) dysfunction, valvular disease or RV infarction4. To understand the role of RV in the pathogenesis of cardiac diseases, a reliable and noninvasive method to access the RV structurally and functionally is essential.
A noninvasive trans-thoracic echocardiography (TTE) based methodology was established and validated for monitoring dynamic changes in RV structure and function in adult mice. To impose RV stress, we employed a surgical model of pulmonary artery constriction (PAC) and measured the RV response over a 7-day period using a high-frequency ultrasound microimaging system. Sham operated mice were used as controls. Images were acquired in lightly anesthetized mice at baseline (before surgery), day 0 (immediately post-surgery), day 3, and day 7 (post-surgery). Data was analyzed offline using software.
Several acoustic windows (B, M, and Color Doppler modes), which can be consistently obtained in mice, allowed for reliable and reproducible measurement of RV structure (including RV wall thickness, end-diastolic&#160;and end-systolic dimensions), and function (fractional area change, fractional shortening, PA peak velocity, and peak pressure gradient) in normal mice and following PAC.
Using this method, the pressure-gradient resulting from PAC was accurately measured in real-time using Color Doppler mode and was comparable to direct pressure measurements performed with a Millar high-fidelity microtip catheter. Taken together, these data demonstrate that RV measurements obtained from various complimentary views using echocardiography are reliable, reproducible and can provide insights regarding RV structure and function. This method will enable a better understanding of the role of RV cardiac dysfunction.

Right ventricle (RV) dysfunction is critical to the pathogenesis of cardiovascular disease, yet limited methodologies are available for its evaluation. Recent advances in ultrasound imaging provide a noninvasive and accurate option for longitudinal RV study. Herein, we detail a step-by-step echocardiographic method using a murine model of RV pressure overload.

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, ...

Chronic Thromboembolic Pulmonary Hypertension and Assessment of Right Ventricular Function in the Piglet

An original piglet model of Chronic Thromboembolic Pulmonary Hypertension (CTEPH) associated with chronic Right Ventricular (RV) dysfunction is described. Pulmonary Hypertension (PH) was induced in 3-week-old piglets by a progressive obstruction of the pulmonary vascular bed. A ligation of the left Pulmonary Artery (PA) was performed first through a mini-thoracotomy. Second, weekly embolizations of the right lower pulmonary lobe were done under fluoroscopic guidance with n-butyl-2-cyanoacrylate during 5 weeks. Mean Pulmonary Arterial Pressure (mPAP) measured by ritght heart catheterism, increased progressively, as well as Right Atrial pressure and Pulmonary Vascular Resistances (PVR) after 5 weeks compared to sham animals. Right Ventricular (RV) structural and functional remodeling were assessed by transthoracic echocardiography (RV diameters, RV wall thickness, RV systolic function). RV elastance and RV-pulmonary coupling were assessed by Pressure-Volume Loops (PVL) analysis with conductance method. Histologic study of the lung and the right ventricle were also performed. Molecular analyses on RV fresh tissues could be performed through repeated transcutaneous endomyocardial biopsies. Pulmonary microvascular disease in obstructed and unobstructed territories was studied from lung biopsies using molecular analyses and pathology. Furthermore, the reliability and the reproducibility was associated with a range of PH severity in animals. Most aspects of the human CTEPH disease were reproduced in this model, which allows new perspectives for the understanding of the underlying mechanisms (mitochondria, inflammation) and new therapeutic approaches (targeted, cellular or gene therapies) of the overloaded right ventricle but also pulmonary microvascular disease.

Chronic Thromboembolic Pulmonary Hypertension (CTEPH) and Right Ventricular (RV) dysfunction were induced in piglets by progressive obstruction of the pulmonary arteries. Consequences were remarkably similar to those observed in CTEPH patients. This animal model would be a very useful tool for pathophysiology and therapeutic experiments on CTEPH and RV failure.

An original piglet model of Chronic Thromboembolic Pulmonary Hypertension (CTEPH) associated with chronic Right Ventricular (RV) dysfunction is described. ...

Shunt Surgery, Right Heart Catheterization, and Vascular Morphometry in a Rat Model for Flow-induced Pulmonary Arterial Hypertension

In this protocol, PAH is induced by combining a 60 mg/kg monocrotalin (MCT) injection with increased pulmonary blood flow through an aorto-caval shunt (MCT+Flow). The shunt is created by inserting an 18-G needle from the abdominal aorta into the adjacent caval vein. Increased pulmonary flow has been demonstrated as an essential trigger for a severe form of PAH with distinct phases of disease progression, characterized by early medial hypertrophy followed by neointimal lesions and the progressive occlusion of the small pulmonary vessels. To measure the right heart and pulmonary hemodynamics in this model, right heart catheterization is performed by inserting a rigid cannula containing a flexible ball-tip catheter via the right jugular vein into the right ventricle. The catheter is then advanced into the main and the more distal pulmonary arteries. The histopathology of the pulmonary vasculature is assessed qualitatively, by scoring the pre- and intra-acinar vessels on the degree of muscularization and the presence of a neointima, and quantitatively, by measuring the wall thickness, the wall-lumen ratios, and the occlusion score.

This protocol describes a surgical procedure to create a model for flow-induced pulmonary arterial hypertension (PAH) in rats and the procedures to analyze the principle hemodynamic and histological end-points in this model.

In this protocol, PAH is induced by combining a 60 mg/kg monocrotalin (MCT) injection with increased pulmonary blood flow through an aorto-caval shunt ...

Tachycardia-Induced Cardiomyopathy As a Chronic Heart Failure Model in Swine

A stable and reliable model of chronic heart failure is required for many experiments to understand hemodynamics or to test effects of new treatment methods. Here, we present such a model by tachycardia-induced cardiomyopathy, which can be produced by rapid cardiac pacing in swine.
A single pacing lead is introduced transvenously into fully anaesthetized healthy swine, to the apex of the right ventricle, and fixated. Its other end is then tunneled dorsally to the paravertebral region. There, it is connected to an in-house modified heart pacemaker unit that is then implanted in a subcutaneous pocket. 
After 4 - 8 weeks of rapid ventricular pacing at rates of 200 - 240 beats/min, physical examination revealed signs of severe heart failure - tachypnea, spontaneous sinus tachycardia, and fatigue. Echocardiography and X-ray showed dilation of all heart chambers, effusions, and severe systolic dysfunction. These findings correspond well to decompensated dilated cardiomyopathy and are also preserved after the cessation of pacing.
This model of tachycardia-induced cardiomyopathy can be used for studying the pathophysiology of progressive chronic heart failure, especially hemodynamic changes caused by new treatment modalities like mechanical circulatory supports. This methodology is easy to perform and the results are robust and reproducible.

Here, we present a protocol to produce tachycardia-induced cardiomyopathy in swine. This model represents a potent way to study the hemodynamics of progressive chronic heart failure and the effects of applied treatment.

A stable and reliable model of chronic heart failure is required for many experiments to understand hemodynamics or to test effects of new treatment ...

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 ...

Induction and Phenotyping of Acute Right Heart Failure in a Large Animal Model of Chronic Thromboembolic Pulmonary Hypertension

The development of acute right heart failure (ARHF) in the context of chronic pulmonary hypertension (PH) is associated with poor short-term outcomes. The morphological and functional phenotyping of the right ventricle is of particular importance in the context of hemodynamic compromise in patients with ARHF. Here, we describe a method to induce ARHF in a previously described large animal model of chronic PH, and to phenotype, dynamically, right ventricular function using the gold standard method (i.e., pressure-volume PV loops) and with a non-invasive clinically available method (i.e., echocardiography). Chronic PH is first induced in pigs by left pulmonary artery ligation and right lower lobe embolism with biological glue once a week for 5 weeks. After 16 weeks, ARHF is induced by successive volume loading using saline followed by iterative pulmonary embolism until the ratio of the systolic pulmonary pressure over systemic pressure reaches 0.9 or until the systolic systemic pressure decreases below 90 mmHg. Hemodynamics are restored with dobutamine infusion (from 2.5 &#181;g/kg/min to 7.5 &#181;g/kg/min). PV-loops and echocardiography are performed during each condition. Each condition requires around 40 minutes for induction, hemodynamic stabilization and data acquisition. Out of 9 animals, 2 died immediately after pulmonary embolism and 7 completed the protocol, which illustrates the learning curve of the model. The model induced a 3-fold increase in mean pulmonary artery pressure. The PV-loop analysis showed that ventriculo-arterial coupling was preserved after volume loading, decreased after acute pulmonary embolism and was restored with dobutamine. Echocardiographic acquisitions allowed to quantify right ventricular parameters of morphology and function with good quality. We identified right ventricular ischemic lesions in the model. The model can be used to compare different treatments or to validate non-invasive parameters of right ventricular morphology and function in the context of ARHF.

We present a protocol to induce and phenotype an acute right heart failure in a large animal model with chronic pulmonary hypertension. This model can be used to test therapeutic interventions, to develop right heart metrics&#160;or to improve the understanding of acute right heart failure pathophysiology.

The development of acute right heart failure (ARHF) in the context of chronic pulmonary hypertension (PH) is associated with poor short-term outcomes. The ...

Invasive Hemodynamic Assessment for the Right Ventricular System and Hypoxia-Induced Pulmonary Arterial Hypertension in Mice

Pulmonary arterial hypertension (PAH) is a chronic and severe cardiopulmonary disorder. Mice are a popular animal model used to mimic this disease. However, the evaluation of right ventricular pressure (RVP) and pulmonary artery pressure (PAP) remains technically challenging in mice. RVP and PAP are more difficult to measure than left ventricular pressure because of the anatomical differences between the left and right heart systems. In this paper, we describe a stable right heart hemodynamic measurement method and its validation using healthy and PAH mice. This method is based on open-chest surgery and mechanical ventilation support. It is a complicated procedure compared to closed chest procedures. While a well-trained surgeon is required for this surgery, the advantage of this procedure is that it can generate both RVP and PAP parameters at the same time, so it is a preferable procedure for the evaluation of PAH models.

Here, we present a protocol to perform an invasive hemodynamic assessment of the right ventricle and pulmonary artery in mice using an open-chest surgery approach.

Pulmonary arterial hypertension (PAH) is a chronic and severe cardiopulmonary disorder. Mice are a popular animal model used to mimic this disease. ...

A Rat Model of Pressure Overload Induced Moderate Remodeling and Systolic Dysfunction as Opposed to Overt Systolic Heart Failure

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation of signal transduction pathways, to counteract, in the short-term, for the cardiac myocyte loss and or the increase in wall stress. However, prolonged activation of these pathways becomes detrimental leading to the initiation and propagation of cardiac remodeling leading to changes in left ventricular geometry and increases in left ventricular volumes; a phenotype seen in patients with systolic heart failure (HF). Here, we describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction (MOD) by ascending aortic banding (AAB) via a vascular clip with an internal area of 2 mm2. The surgery is performed in 200 g Sprague-Dawley rats. The MOD HF phenotype develops at 8-12 weeks after AAB and is characterized noninvasively by means of echocardiography. Previous work suggests the activation of signal transduction pathways and altered gene expression and post-translational modification of proteins in the MOD HF phenotype that mimic those seen in human systolic HF; therefore, making the MOD HF phenotype a suitable model for translational research to identify and test potential therapeutic anti-remodeling targets in HF. The advantages of the MOD HF phenotype compared to the overt systolic HF phenotype is that it allows for the identification of molecular targets involved in the early remodeling process and the early application of therapeutic interventions. The limitation of the MOD HF phenotype is that it may not mimic the spectrum of diseases leading to systolic HF in human. Moreover, it is a challenging phenotype to create, as the AAB surgery is associated with high mortality and failure rates with only 20% of operated rats developing the desired HF phenotype.

We describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction where signal transduction pathways involved in the initiation of the remodeling process are activated. This animal model will aid in identifying molecular targets for applying early therapeutic anti-remodeling strategies for heart failure.

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation ...

Generation and Characterization of Right Ventricular Myocardial Infarction Induced by Permanent Ligation of the Right Coronary Artery in Mice

Right ventricular infarction (RVI) is a common presentation in clinical practice. Severe RVI can lead to fatal hemodynamic dysfunction and arrhythmia. In contrast to the extensively used mouse myocardial infarction (MI) model generated by left coronary artery ligation, the RVI mouse model is rarely employed due to the difficulty associated with model generation. Research on the mechanisms and treatment of RVI-induced RV remodeling and dysfunction requires animal models to mimic the pathophysiology of RVI in patients. This study introduces a feasible procedure for RVI model generation in C57BL/6J mice. Further, this model was characterized based on the following: infarct size evaluation at 24 h after MI, assessment of cardiac remodeling and function with echocardiography, RV hemodynamics assessment, and histology of the infarct zone at 4 weeks after RVI. In addition, a coronary vasculature cast was performed to observe the coronary arterial arrangement in RV. This mouse model of RVI would facilitate the research on mechanisms of right heart failure and seek new therapeutic targets of RV remodeling.

There are several differences between the right and left ventricles. However, the pathophysiology of right ventricular infarction (RVI) has not been clarified. In the present protocol, a reproducible method for RVI mouse model generation is introduced, which may provide a means to explain the mechanism of RVI.

Right ventricular infarction (RVI) is a common presentation in clinical practice. Severe RVI can lead to fatal hemodynamic dysfunction and arrhythmia. In ...