NIH grant HL070241 to P.D.

All methods and procedures described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Tulane University School of Medicine.
1. Tools and instruments for AAB model creation
<ol>
	<li>Obtain disinfectants, such as 70% isopropyl alcohol and povidone-iodine.</li>
	<li>Obtain ketamine and xylazine for anesthesia and buprenorphine for analgesia.</li>
	<li>Obtain a heating pad and heavy absorbency disposable underpad with the dimensions of 18 inches x 30 inches.</li>
	<li>Obtain a 100% cotton twine roll, a tape and a hair clipper.</li>
	<li>Obtain a 20 cm x 25 cm plastic board, thickness range between 3-5 mm.</li>
	<li>Obtain a Z-LITE fiber optic illuminator.</li>
	<li>Obtain a mechanical ventilator for small animals (e.g., SAR-830/AP).</li>
	<li>Obtain 2-0 and 3-0 Vicryl taper sutures and nylon 3-0 monofilament suture, sterile gauze pads and sterile extra large cotton tips and sterile gloves.</li>
	<li>Obtain 16 G angiocath for intubation.</li>
	<li>Purchase the following surgical tools.
	<ol>
		<li>Obtain a Weck stainless steel Hemoclip ligation and stainless-steel ligating clips.</li>
		<li>Obtain hardened fine iris scissors.</li>
		<li>Obtain Adson forceps.</li>
		<li>Obtain two curved Graefe forceps.</li>
		<li>Obtain a Halsted-Mosquito Hemostats-straight forceps.</li>
		<li>Obtain a Mayo-Hegar needle holder.</li>
		<li>Obtain an Alm chest retractor with blunt teeth.</li>
	</ol>
	</li>
	<li>Utilize and obtain an autoclave and a bead sterilizer.</li>
</ol>
2. Ascending aortic banding surgical procedure
<ol>
	<li>Anesthetize the animal with an intraperitoneal injection of a mix of 75-100 mg/kg Ketamine and 10 mg/kg Xylazine. 
	NOTE: Allow a few minutes for the animal to be completely sedated and flaccid. If the anesthetic dose is not sufficient and the animal is still moving in the cage, re-inject the animal with the same anesthetic dose after allowing enough time, around 5-10 minutes between subsequent injections. Most animals require 1-2 injections to achieve deep sedation and anesthesia.</li>
	<li>Shave the hair on the surgical site located at the right lateral thoracic area under the right armpit.</li>
	<li>Stabilize the animal by gently taping all four limbs to the plastic board. Then perform endotracheal intubation with a 16 G angiocath. After the animal is successfully intubated, initiate mechanical ventilation with tidal volumes of 2 mL at 50 cycles/min and FiO2 of 21%. Look for the symmetrical rise in chest wall with each breath.</li>
	<li>Turn the animal slowly to lie on its left lateral side, and then bend the tail in a U-shape manner and stabilize it by gently taping it to the plastic board. Then go ahead and disinfect the shaved area with topical application of povidone-iodine.&#160;</li>
	<li>Infiltrate the skin at the incision site with 50/50 mix by volume of 1-2% Lidocaine/0.25-0.5 % Bupivacaine as preemptive analgesia before making the incision.</li>
	<li>Perform a right horizontal skin incision, 1-2 centimeters long, in the right axillary area 1 cm below the right armpit. Then, dissect the thoracic muscular layer until reaching the thoracic rib cage. Make a 1 cm thoracotomy between the 2nd and 3rd rib cage.
	<ol>
		<li>While dissecting the muscular layer of the chest, be careful and avoid injury of the right axillary artery, which runs underneath the right armpit. 
		NOTE: Thoracotomy performed between the 1st and the 2nd rib carries the risk of banding the right brachiocephalic artery instead of the ascending aorta. Thoracotomy between the 3rd and the fourth rib makes it hard to visualize and band the ascending aorta, as the operator will be looking at the right atrium. 
		NOTE: Avoid extending the thoracotomy too medially towards the sternum to avoid dissecting and injuring the right internal mammary artery.</li>
	</ol>
	</li>
	<li>Dissect the two lobes of the thymus gland gently and push them apart on the side. Then identify the ascending aorta and isolate it from the superior vena cava by blunt dissection via a curved Graefe forceps. 
	NOTE: Significant manipulation of the thymus gland will render it swollen and makes it hard to visualize the ascending aorta.
	<ol>
		<li>Dissect the superior vena cava from the aorta with extra caution to avoid injury or rupture of the superior vena cava, which is fatal. This may be the trickiest part of the procedure and is expected to happen from time to time even in most experienced hands, but often with beginners and learners.</li>
	</ol>
	</li>
	<li>Lift gently the ascending aorta with a curved Graefe forceps and place the vascular clip around the ascending aorta.
	<ol>
		<li>Adjust the vascular hemoclip ligation tool via a plastic pre-cut 7&#34; piece to obtain a vascular clip of the desired internal area of 1.5 mm2 or 2 mm2, depending on which HF model is desired.</li>
	</ol>
	</li>
	<li>Suture the thorax via a Vicryl 2-0 monofilament suture. Then suture the muscular layer of the chest via a 3-0 Vicryl taper suture. Then suture the skin incision via a Nylon 3-0 monofilament suture.</li>
	<li>Administer a combination of the following drugs after completion of the surgery for 48-72 hrs to serve as analgesia in the post-operative period: 1) Buprenorphine 0.01-0.05 mg/kg subcutaneously every 8-12h, 2) Meloxicam 2 mg/kg subcutaneously every 12h, and 3) Morphine 2.5 mg/kg subcutaneously every 2-4h as needed for severe pain. 
	NOTE: Leave the animal to recover on a heating pad under regular monitoring. Once the animal shows signs of recovery from anesthesia (able to breath spontaneously - without evidence of gasping or use of accessory muscles for more than two minutes - and has good reflexes, red and warm extremities), extubate the animal and return it to the cage.</li>
</ol>
3. Echocardiography
<ol>
	<li>Sedate the animal with intraperitoneal injection of 80-100 mg/kg ketamine. Ensure adequate sedation for proper acquisition of good quality echo images. 
	NOTE: The use of isoflurane as an anesthetic is discouraged for its cardiodepressor effect, especially in the setting of severe pressure overload and might give a false impression of LV dilatation and systolic dysfunction that resolves once animal is off anesthetic.
	<ol>
		<li>Be cautious and administer half or even one third of the dose of ketamine in animals that look dyspneic and tachypneic with suspicion that they have developed the HFrEF phenotype.</li>
	</ol>
	</li>
	<li>Shave the hair of the chest, anteriorly, in the completely sedated animal.</li>
	<li>Lay the animal on its back and stabilize it to the plastic board.</li>
	<li>Acquire 2D parasternal long axis and 2D parasternal short axis view clips at the level of the papillary muscle. Also, obtain M-mode images from the short parasternal axis view at the level of the papillary muscle to measure LV septal and posterior wall thickness in diastole as well as LV end-diastolic and end-systolic diameter.
	<ol>
		<li>Acquire images or clips at a heart rate of 370 - 420 beats per minute to ensure proper assessment of LV size and function. Acquisition of images at lower heart rates will lead to a false impression of depressed LV function and LV dilatation. 
		NOTE: Acquisition of foreshortened 2D long parasternal axis view images/clips lead to false measurements. For quality control purposes, make sure that the LV apex and the aorto-mitral angle are visualized within the same plane cut.</li>
		<li>Acquire 2D short parasternal axis view images/clips at the level of the mid papillary muscle. This will serve as a reference to obtain reliable serial and subsequent LV measurements while following the animals over time throughout the study period.</li>
	</ol>
	</li>
	<li>Obtain M-mode images in long parasternal axis view at the level of the aortic valve to assess the relative aortic to left atrium (LA) diameter at end systole. 
	NOTE: Animals with the MOD and HFrEF phenotypes should show evidence of LA dilatation with LA/Ao ratio being &#8805;1.25 and &#60;1.5 in MOD HF phenotype and &#8805;1.5 in the HFrEF phenotype10.</li>
</ol>

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A., Hill, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autophagy+in+load-induced+heart+disease.">Autophagy in load-induced heart disease.</a> Circulation Research. 103 (12), 1363-1369 (2008).</li><li>Barrick, C. 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=Parent-of-origin+effects+on+cardiac+response+to+pressure+overload+in+mice.">Parent-of-origin effects on cardiac response to pressure overload in mice.</a> American Journal of Physiology-Heart and Circulatory Physiology. 297 (3), H1003-H1009 (2009).</li><li>Barrick, C. J., Rojas, M., Schoonhoven, R., Smyth, S. 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All authors report no conflict of interest.

Following PO related to AAB in rat, the LV undergoes concentric remodeling by increasing LV wall thickness, known as concentric LVH, as a compensatory mechanism to counteract for the increase in LV wall stress. Increase in LV wall thickness becomes noticeable during the first week following AAB and reaches its maximum thickness at 2-3 weeks post-AAB. During this time period, activation of maladaptive signal transduction pathways lead to progressive enlargement of the LV with increases in LV volumes, a process known as ec...

Heart failure (HF) is a prevalent disease and is associated with high morbidity and mortality1. Rodent pressure-overload (PO) models of HF, produced by ascending or transverse aortic banding, are commonly used to explore molecular mechanisms leading to HF and to test potential novel therapeutic targets in HF. They also mimic changes seen in human HF secondary to prolonged systemic hypertension or severe aortic stenosis. Following PO, the left ventricular (LV) wall gradually increases in thickness, a process known as concentric LV hypertrophy (LVH), to compensate and adapt for the increase in LV wall stress. However, this is associated with the activation of a number of maladaptive signaling pathways, which lead to derangements in calcium cycling and homeostasis, metabolic and extracellular matrix remodeling and changes in gene expression as well as enhanced apoptosis and autophagy2,3,4,5,6. These molecular changes constitute the trigger for the initiation and propagation of myocardial remodeling and transition into a decompensated HF phenotype.
Despite the use of inbred rodent strains and standardization of clip size and surgical technique, there is tremendous phenotypic variability in LV chamber structure and function in aortic banding models7,8,9. The phenotypic variability encountered after PO in rat, Sprague-Dawley strain, is described elsewhere10,11. Of those, two HF phenotypes are encountered with evidence of myocardial remodeling and activation of signal transduction pathways leading to a state of heightened oxidative stress. This is associated with metabolic remodeling, altered gene expression and changes in posttranslational modification of proteins, altogether playing a role in the remodeling process10,12. The first is a phenotype of moderate remodeling and early systolic dysfunction (MOD) and the second is a phenotype of overt systolic HF (HFrEF).
The PO model of HF is advantageous over the myocardial infarction (MI) model of HF because the PO-induced circumferential and meridional wall stresses are homogeneously distributed across all segments of the myocardium. However, both models suffer from variability in the severity of PO10,11 and in infarct size13,14 along with intense inflammation and scarring at the infarct site15 as well as adhesion to the chest wall and surrounding tissues, which are observed in the MI model of HF. Moreover, the rat PO induced HF model is challenging to create as it is associated with high mortality and failure rates10, with only 20% of the operated rats developing the MOD HF phenotype10.
The MOD is an attractive HF phenotype and constitutes an evolution of the traditionally created HFrEF phenotype as it allows for early targeting of signal transduction pathways that play a role in myocardial remodeling, especially when it pertains to perturbations in mitochondrial dynamics and function, myocardial metabolism, calcium cycling and extracellular matrix remodeling. These pathophysiological processes are highly evident in the MOD HF phenotype11. In this manuscript, we describe how to create the MOD and HFrEF phenotypes and we address pitfalls while performing the ascending aortic banding (AAB) procedure. We also elaborate on how to best characterize by echocardiography the two HF phenotypes, MOD and HFrEF, and how to differentiate them from other phenotypes that fail to develop severe PO or that develop severe PO and concentric remodeling but without significant eccentric remodeling.

<table><tbody><tr><td>Adson forceps</td><td>F.S.T.</td><td>11019-12</td><td>surgical tool</td></tr><tr><td>Alm chest retractor with blunt teeth</td><td>ROBOZ</td><td>RS-6510</td><td>surgical tool</td></tr><tr><td>Graefe forceps, curved</td><td>F.S.T.</td><td>11152-10</td><td>surgical tool</td></tr><tr><td>Halsted-Mosquito Hemostats, straight</td><td>F.S.T.</td><td>13010-12</td><td>surgical tool</td></tr><tr><td>Hardened fine iris scissors, straight</td><td>Fine Science Tools F.S.T.</td><td>14090-11</td><td>surgical tool</td></tr><tr><td>hemoclip traditional-stainless steel ligating clips</td><td>Weck</td><td>523735</td><td>surgical tool</td></tr><tr><td>Mayo-Hegar needle holder</td><td>F.S.T.</td><td>12004-18</td><td>surgical tool</td></tr><tr><td>mechanical ventilator</td><td>CWE inc</td><td>SAR-830/AP</td><td>mechanical ventilator for small animals</td></tr><tr><td>Weck stainless steel Hemoclip ligation</td><td>Weck</td><td>533140</td><td>surgical tool</td></tr></tbody></table>

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.

Characterization of the HF phenotypes, that develop 8-12 weeks following AAB, could be easily performed via echocardiography. Representative M-mode images of Sham, Week 3 post-AAB, MOD and HFrEF phenotypes are presented in Figure 1A. Figure 1B and Figure 1C are showing the vascular clip size for the creation of the MOD HF phenotype and HFrEF phenotype, respective...

Watch this Scientific Journal Video about A Rat Model of Pressure Overload Induced Moderate Remodeling and Systolic Dysfunction as Opposed to Overt Systolic Heart Failure at JoVE.com

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

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 ...

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6.4K Views.  Tulane University. De rat druk overbelasting geïnduceerde matige remodelleren en vroege systolische disfunctie model is een mildere versie van de eerder gecreëerde rat druk overbelasting geïnduceerd voor systolisch hartfalen model. De studie die ik liefheb, studie van de trajecten die betrokken zijn bij de initiatie en voortplanting van cardiale remodellering, vooral omdat het gaat om metabole remodellering, myocardiale disfunctie, en calcium fietsen. Pas voor het begin van de procedure een vasculaire hemocl...

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

Permanent Ligation of the Left Anterior Descending Coronary Artery in Mice: A Model of Post-myocardial Infarction Remodelling and Heart Failure

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It is characterized by fluid retention, shortness of breath, and fatigue, in particular on exertion. Heart failure is a growing public health problem, the leading cause of hospitalization, and a major cause of mortality. Ischemic heart disease is the main cause of heart failure.
Ventricular remodelling refers to changes in structure, size, and shape of the left ventricle. This architectural remodelling of the left ventricle is induced by injury (e.g., myocardial infarction), by pressure overload (e.g., systemic arterial hypertension or aortic stenosis), or by volume overload. Since ventricular remodelling affects wall stress, it has a profound impact on cardiac function and on the development of heart failure. A model of permanent ligation of the left anterior descending coronary artery in mice is used to investigate ventricular remodelling and cardiac function post-myocardial infarction. This model is fundamentally different in terms of objectives and pathophysiological relevance compared to the model of transient ligation of the left anterior descending coronary artery. In this latter model of ischemia/reperfusion injury, the initial extent of the infarct may be modulated by factors that affect myocardial salvage following reperfusion. In contrast, the infarct area at 24 hr after permanent ligation of the left anterior descending coronary artery is fixed. Cardiac function in this model will be affected by 1) the process of infarct expansion, infarct healing, and scar formation; and 2) the concomitant development of left ventricular dilatation, cardiac hypertrophy, and ventricular remodelling.
Besides the model of permanent ligation of the left anterior descending coronary artery, the technique of invasive hemodynamic measurements in mice is presented in detail.

Heart failure is the leading cause of hospitalization and a major cause of mortality. A model of permanent ligation of the left anterior descending coronary artery in mice is applied to investigate ventricular remodelling and cardiac dysfunction post-myocardial infarction. The technique of invasive hemodynamic measurements in mice is presented.

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It ...

A Model of Cardiac Remodeling Through Constriction of the Abdominal Aorta in Rats

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and fluid retention. Changes in myocardial structure, electrical conduction, and energy metabolism develop with heart failure, leading to contractile dysfunction, increased risk of arrhythmias, and sudden death. Hypertensive heart disease is one of the key contributing factors of cardiac remodeling associated with heart failure. The most commonly-used animal model mimicking hypertensive heart disease is created via surgical interventions, such as by narrowing the aorta. Abdominal aortic constriction is a useful experimental technique to induce a pressure overload, which leads to heart failure. The surgery can be easily performed, without the need for chest opening or mechanical ventilation. Abdominal aortic constriction-induced cardiac pathology progresses gradually, making this model relevant to clinical hypertensive heart failure. Cardiac injury and remodeling can be observed 10 weeks after the surgery. The method described here provides a simple and effective approach to produce a hypertensive heart disease animal model that is suitable for studying disease mechanisms and for testing novel therapeutics.

A rat model of abdominal aortic constriction that induces cardiac hypertrophy and remodeling is described. An efficient, highly-reproducible, and minimally-invasive method is used to provide a simple yet useful platform for research in myocardial hypertrophy and dysfunction.

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and ...

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.

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 ...

Studying Left Ventricular Reverse Remodeling by Aortic Debanding in Rodents

To better understand the left ventricular (LV) reverse remodeling (RR), we describe a rodent model wherein, after aortic banding-induced LV remodeling, mice undergo RR upon removal of the aortic constriction. In this paper, we describe a step-by-step procedure to perform a minimally invasive surgical aortic debanding in mice. Echocardiography was subsequently used to assess the degree of cardiac hypertrophy and dysfunction during LV remodeling and RR and to determine the best timing for aortic debanding. At the end of the protocol, terminal hemodynamic evaluation of the cardiac function was conducted, and samples were collected for histological studies. We showed that debanding is associated with surgical survival rates of 70-80%. Moreover, two weeks after debanding, the significant reduction of ventricular afterload triggers the regression of ventricular hypertrophy (~20%) and fibrosis (~26%), recovery of diastolic dysfunction as assessed by the normalization of left ventricular filling and end-diastolic pressures (E/e&#39;&#160;and LVEDP). Aortic debanding is a useful experimental model to study LV RR in rodents. The extent of myocardial recovery is variable between subjects, therefore, mimicking the diversity of RR that occurs in the clinical context, such as aortic valve replacement. We conclude that the aortic banding/debanding model represents a valuable tool to unravel novel insights into the mechanisms of RR, namely the regression of cardiac hypertrophy and the recovery of diastolic dysfunction.

Here we describe a step-by-step protocol of surgical aorta debanding in the well-established mice model of aortic-constriction. This procedure not only allows studying the mechanisms underlying the left ventricular reverse remodeling and regression of hypertrophy but also to test novel therapeutic options that might accelerate myocardial recovery.

To better understand the left ventricular (LV) reverse remodeling (RR), we describe a rodent model wherein, after aortic banding-induced LV remodeling, ...

Quantification of Biventricular Function and Morphology by Cardiac Magnetic Resonance Imaging in Mice with Pulmonary Artery Banding

Right ventricular (RV) function and failure are major determinants of outcome in acquired and congenital heart diseases, including pulmonary hypertension. Assessment of RV function and morphology is complex, partly due to the complex shape of the RV. Currently, cardiac magnetic resonance (CMR) imaging is the golden standard for noninvasive assessment of RV function and morphology. The current protocol describes CMR imaging in a mouse model of RV pressure load induced by pulmonary artery banding (PAB). PAB is performed by placing a 6-0 suture around the pulmonary artery over a 23 G needle. The PAB gradient is determined using echocardiography at 2 and 6 weeks. At 6 weeks, the right and left ventricular morphology and function is assessed by measuring both end-systolic and end-diastolic volumes and mass by ten to eleven cine slices 1 mm thick using a 9.4 T magnetic resonance imaging scanner equipped with a 1,500 mT/m gradient. Representative results show that PAB induces a significant increase in RV pressure load, with significant effects on biventricular morphology and RV function. It is also shown that at 6 weeks of RV pressure load, cardiac output is maintained. Presented here is a reproducible protocol for the quantification of biventricular morphology and function in a mouse model of RV pressure load and may serve as a method for experiments exploring determinants of RV remodeling and dysfunction.

To understand the pathophysiology of right ventricular (RV) adaptation to abnormal loading, experimental models are crucial. However, assessment of RV dimensions and function is complex and challenging. This protocol provides a method to perform cardiac magnetic resonance imaging (CMR) as a noninvasive benchmark procedure in mice subjected to RV pressure load.

Right ventricular (RV) function and failure are major determinants of outcome in acquired and congenital heart diseases, including pulmonary hypertension. ...

An Image Guided Transapical Mitral Valve Leaflet Puncture Model of Controlled Volume Overload from Mitral Regurgitation in the Rat

Mitral regurgitation (MR) is a widely prevalent heart valve lesion, which causes cardiac remodeling and leads to congestive heart failure. Though the risks of uncorrected MR and its poor prognosis are known, the longitudinal changes in cardiac function, structure and remodeling are incompletely understood. This knowledge gap has limited our understanding of the optimal timing for MR correction, and the benefit that early versus late MR correction may have on the left ventricle. To investigate the molecular mechanisms that underlie left ventricular remodeling in the setting of MR, animal models are necessary. Traditionally, the aorto-caval fistula model has been used to induce volume overload, which differs from clinically relevant lesions such as MR. MR represents a low-pressure volume overload hemodynamic stressor, which requires animal models that mimic this condition. Herein, we describe a rodent model of severe MR in which the anterior leaflet of the rat mitral valve is perforated with a 23G needle, in a beating heart, with echocardiographic image guidance. The severity of MR is assessed and confirmed with echocardiography, and the reproducibility of the model is reported.&#160;&#160;

A rodent model of left heart volume overload from mitral regurgitation is reported. Mitral regurgitation of controlled severity is induced by advancing a needle of defined dimensions into the anterior leaflet of the mitral valve, in a beating heart, with ultrasound guidance.&#160;

Mitral regurgitation (MR) is a widely prevalent heart valve lesion, which causes cardiac remodeling and leads to congestive heart failure. Though the ...

A Model of Reverse Vascular Remodeling in Pulmonary Hypertension Due to Left Heart Disease by Aortic Debanding in Rats

Pulmonary hypertension due to left heart disease (PH-LHD) is the most common form of PH, yet its pathophysiology is poorly characterized than pulmonary arterial hypertension (PAH). As a result, approved therapeutic interventions for the treatment or prevention of PH-LHD are missing. Medications used to treat PH in PAH patients are not recommended for treatment of PH-LHD, as reduced pulmonary vascular resistance (PVR) and increased pulmonary blood flow in the presence of increased left-sided filling pressures may cause left heart decompensation and pulmonary edema. New strategies need to be developed to reverse PH in LHD patients. In contrast to PAH, PH-LHD develops due to increased mechanical load caused by congestion of blood into the lung circulation during left heart failure. Clinically, mechanical unloading of the left ventricle (LV) by aortic valve replacement in aortic stenosis patients or by implantation of LV assist devices in end-stage heart failure patients normalizes not only pulmonary arterial and right ventricular (RV) pressures but also PVR, thus providing indirect evidence for reverse remodeling in the pulmonary vasculature. Using an established rat model of PH-LHD due to left heart failure triggered by pressure overload with subsequent development of PH, a model is developed to study the molecular and cellular mechanisms of this physiological reverse remodeling process. Specifically, an aortic debanding surgery was performed, which resulted in reverse remodeling of the LV myocardium and its unloading. In parallel, complete normalization of RV systolic pressure and significant but incomplete reversal of RV hypertrophy was detectable. This model may present a valuable tool to study the mechanisms of physiological reverse remodeling in the pulmonary circulation and the RV, aiming to develop therapeutic strategies for treating PH-LHD and other forms of PH.

The present protocol describes a surgical procedure to remove ascending-aortic banding in a rat model of pulmonary hypertension due to left heart disease. This technique studies endogenous mechanisms of reverse remodeling in the pulmonary circulation and the right heart, thus informing strategies to reverse pulmonary hypertension and/or right ventricular dysfunction.

Pulmonary hypertension due to left heart disease (PH-LHD) is the most common form of PH, yet its pathophysiology is poorly characterized than pulmonary ...

O-Ring Aortic Banding Versus Traditional Transverse Aortic Constriction for Modeling Pressure Overload-Induced Cardiac Hypertrophy

Aortic banding in mice is one of the most commonly used experimental models for cardiac pressure overload-induced cardiac hypertrophy and the induction of heart failure. The previously used technique is based on a threaded suture around the aortic arch tied over a blunted 27 G needle to create stenosis. This method depends on the surgeon manually tightening the thread and, thus, leads to high variance in the diameter size. A newly refined method described by Melleby et al. promises less variance and more reproducibility after surgery. The new technique, o-ring- aortic banding (ORAB), uses a non-slip rubber ring instead of a suture with a thread, resulting in reduced variation in pressure overload and reproducible phenotypes of cardiac hypertrophy. During surgery, the o-ring is placed between the brachiocephalic and left carotid arteries. Successful constriction is confirmed by echocardiography. After 1 day, correct placement of the ring results in an increased flow velocity in the transverse aorta over the o-ring-induced stenosis. After 2 weeks, impaired cardiac function is proven by decreased ejection fraction and increased wall thickness. Importantly, besides less variance in the diameter size, ORAB is associated with lower intra- and post-operative mortality rates compared with transverse aortic constriction (TAC). Thus, ORAB represents a superior method to the commonly used TAC surgery, resulting in more reproducible results and a possible reduction in the number of animals needed.

The present protocol describes a new technique of aortic banding in mice to induce pressure overload cardiac hypertrophy. For banding, a rubber ring with a fixed inner diameter is used. This new technique promises less variance and more reproducible data for future experiments.

Aortic banding in mice is one of the most commonly used experimental models for cardiac pressure overload-induced cardiac hypertrophy and the induction of ...

Chronic Ovine Model of Right Ventricular Failure and Functional Tricuspid Regurgitation

The pathophysiology of severe functional tricuspid regurgitation (FTR) associated with right ventricular dysfunction is poorly understood, leading to suboptimal clinical results. We set out to establish a chronic ovine model of FTR and right heart failure to investigate the mechanisms of FTR. Twenty adult male sheep (6-12 months old, 62 &#177; 7 kg) underwent a left thoracotomy and baseline echocardiography. A pulmonary artery band (PAB) was placed and cinched around the main pulmonary artery (PA) to at least double the systolic pulmonary artery pressure (SPAP), inducing right ventricular (RV) pressure overload and signs of RV dilatation. PAB acutely increased the SPAP from 21 &#177; 2 mmHg to 62 &#177; 2 mmHg. The animals were followed for 8 weeks, symptoms of heart failure were treated with diuretics, and surveillance echocardiography was used to assess for pleural and abdominal fluid collection. Three animals died during the follow-up period due to stroke, hemorrhage, and acute heart failure. After 2 months, a median sternotomy and epicardial echocardiography were performed. Of the surviving 17 animals, 3 developed mild tricuspid regurgitation, 3 developed moderate tricuspid regurgitation, and 11 developed severe tricuspid regurgitation. Eight weeks of pulmonary artery banding resulted in a stable chronic ovine model of right ventricular dysfunction and significant FTR. This large animal platform can be used to further investigate the structural and molecular basis of RV failure and functional tricuspid regurgitation.

Right ventricular failure and functional tricuspid regurgitation are associated with left-sided heart disease and pulmonary hypertension, which contribute significantly to morbidity and mortality in patients. Establishing a chronic ovine model to study right ventricular failure and functional tricuspid regurgitation will help in understanding their mechanisms, progression, and possible treatments.

The pathophysiology of severe functional tricuspid regurgitation (FTR) associated with right ventricular dysfunction is poorly understood, leading to ...

Creating a Murine Model of RV Hypertrophy and Failure by Pulmonary Trunk Banding

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

Right ventricular (RV) failure caused by pressure overload is strongly associated with morbidity and mortality in a number of cardiovascular and pulmonary diseases. The pathogenesis of RV failure is complex and remains inadequately understood. To identify new therapeutic strategies for the treatment of RV failure, robust and reproducible animal models are essential. Models of pulmonary trunk banding (PTB) have gained popularity, as RV function can be assessed independently of changes in the pulmonary vasculature.
In this paper, we present a murine model of RV pressure overload induced by PTB in 5-week-old mice. The model can be used to induce different degrees of RV pathology, ranging from mild RV hypertrophy to decompensated RV failure. Detailed protocols for intubation, PTB surgery, and phenotyping by echocardiography are included in the paper. Furthermore, instructions for customizing instruments for intubation and PTB surgery are given, enabling fast and inexpensive reproduction of the PTB model.
Titanium ligating clips were used to constrict the pulmonary trunk, ensuring a highly reproducible and operator-independent degree of pulmonary trunk constriction. The severity of PTB was graded by using different inner ligating clip diameters (mild: 450 &#181;m and severe: 250 &#181;m). This resulted in RV pathology ranging from hypertrophy with preserved RV function to decompensated RV failure with reduced cardiac output and extracardiac manifestations. RV function was assessed by echocardiography at 1 week and 3 weeks after surgery. Examples of echocardiographic images and results are presented here. Furthermore, results from right heart catheterization and histological analyses of cardiac tissue are shown.

Author Spotlight: Investigating the Underlying Mechanisms of Right Ventricular Failure in Pulmonary Hypertension

We describe a murine model of right ventricular pressure overload-induced by pulmonary trunk banding. Detailed protocols for intubation, surgery, and phenotyping by echocardiography are included in the paper. Custom-made instruments are used for intubation and surgery, allowing for fast and inexpensive reproduction of the model.

Right ventricular (RV) failure caused by pressure overload is strongly associated with morbidity and mortality in a number of cardiovascular and pulmonary ...

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

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