This research was supported by grants of the DZHK (German Centre for Cardiovascular Research) to CK and WMK, the BMBF (German Ministry of Education and Research) to CK in the framework of VasBio, and to WMK in the framework of VasBio, SYMPATH, and PROVID, and the German Research Foundation (DFG) to WMK (SFB-TR84 A2, SFB-TR84 C9, SFB 1449 B1, SFB 1470 A4, KU1218/9-1, and KU1218/11-1).

All procedures were performed following the &#34;Guide for the Care and Use of Laboratory Animals&#34; (Institute of Laboratory Animal Resources, 8th edition 2011) and approved by the local governmental animal care and use committee of the German State Office for Health and Social Affairs (Landesamt f&#252;r Gesundheit und Soziales (LaGeSO), Berlin; protocol no. G0030/18). First, congestive heart failure was surgically induced in juvenile Sprague-Dawley rats ~100 g body weight (bw) (see Table of Materials) by placing a titanium clip with a 0.8 mm inner diameter on the ascending aorta (aortic banding, AoB) as described previously29,30. At week 3 after AoB (Figure 1), debanding (Deb) surgery was performed to remove the clip from the aorta. The surgical procedures and validation of PH reversal in AoB rats performed are schematically depicted in Figure 1.
1. Surgical preparations
<ol>
	<li>Sterilize the required surgical instruments (Figure 2) by autoclaving.</li>
	<li>Inject rat with carprofen (5 mg/kg bw) (see Table of Materials) intraperitoneally (i.p.) for analgesia 30 min prior to surgery.</li>
	<li>Anesthetize rat by i.p. injection of ketamine (87 mg/kg bw) and xylazine (13 mg/kg bw).</li>
	<li>Remove the hair from the animal&#39;s neckline and chest using an electric shaver.</li>
	<li>Apply a drop of eye ointment to protect the eyes during surgery.</li>
	<li>Place the rat in a supine position on a sterilized surgical table. Carefully fix the animal&#39;s abdomen and limbs with adhesive tape. 
	NOTE: To maintain body temperature, place a 37 &#176;C heating mat under the surgical table. Avoid heating of the head region to prevent drying of eyes.</li>
	<li>Disinfect animal skin with povidone-iodine/iodophor solution. Note scars and sutures from the primary AoB surgery and drape the surgical field.</li>
	<li>Ensure adequate depth of anesthesia by toe pinching. 
	&#8203;NOTE: Depth of anesthesia needs to be controlled regularly during surgery.</li>
</ol>
2. Tracheotomy and mechanical ventilation
NOTE: Throughout the surgery, change gloves after handling non-sterile equipment.
<ol>
	<li>With fine scissors (Figure 2A), make a 7-10 mm long cervical midline incision (Figure 3A).</li>
	<li>With the help of a pair of blunt forceps (Figure 2B&#39;), dissect the cervical soft tissue to expose the infrahyoid muscles. Split muscles in the midline to visualize the trachea. Cut and remove the suture from the primary AoB surgery.</li>
	<li>Make ~2 mm trachea incision between two cartilaginous rings using angled Noyes spring scissors (Figure 2C,3B). Insert the tracheal cannula of outer diameter 2 mm (Figure 2D) into the trachea and secure it with a 4-0 silk suture (Figure 2E,3C).</li>
	<li>Connect the tracheal cannula to a mechanical ventilator (see Table of Materials) while keeping dead space to a minimum (Figure 3D-E). Keep perioperative lung ventilation at a respiratory rate of 90 breaths/min at a tidal volume (Vt) of 8.5 mL/kg bw.</li>
</ol>
3. Aortic debanding
<ol>
	<li>Make an ~20 mm long skin incision between the second and third ribs using fine scissors (Figure 3F).</li>
	<li>With the help of smaller surgical scissors (Figure 2F), carefully spread muscles and cut them layer by layer (Figure 3G). Make a 10 mm lateral incision along the intercostal space between the second and third rib. 
	NOTE: The midsternal line needs to be carefully approached to avoid bleeding.</li>
	<li>Use a rib spreader (Figure 2G) to expand the intercostal space between the second and third rib to create a surgical window (Figure 3H).</li>
	<li>With the help of blunt forceps (Figure 2B,B&#39;), carefully separate the thymus from the heart and conduit arteries to visualize the aorta with the clip (Figure 4A).</li>
	<li>Hold the clip with the help of the forceps and carefully remove the connective tissue around the clip to expose it. 
	NOTE: Avoid holding or lifting the aorta with the forceps, as it may injure the aorta resulting in bleeding and a lethal outcome.</li>
	<li>With the help of a needle holder (Figure 2H), open the clip (Figure 4B) and remove it from the thoracic cavity.</li>
	<li>Before closing the chest, open up lung atelectasis, ensure adequate lung recruitment without overdistension, continue mechanical ventilation with a Vt of 9.5 mL/kg bw for another 10 min, and return to a Vt of 8.5 mL/kg bw to recruit the lungs and resolve a possible pneumothorax.</li>
	<li>Close the deep muscles by a simple interrupted suture using 4-0 silk. Then connect the upper muscles and the skin with a simple continuous suture (Figure 5A,B).</li>
</ol>
4. Tracheal extubation
<ol>
	<li>Disconnect the tracheal cannula from the ventilation machine. Attentively observe the rat until spontaneous breathing is re-established. If the animal fails to breathe spontaneously upon disconnection, reconnect the ventilator and continue ventilating for an additional 5 min. Then repeat the procedure.</li>
	<li>After spontaneous breathing is re-established, remove the cannula from the trachea and clean the liquid around the trachea with sponge points (Figure 2I) (see Table of Materials).</li>
	<li>Close the trachea with a simple suture using 6-0 prolene (Figure 2E&#39; and Figure 5C). Then close infrahyoid muscles in a simple interrupted suture using 4-0 silk (Figure 5D), and connect the skin in a simple continuous suture (Figure 5E). Clean and disinfect the muscles and the skin during the process with povidone-iodine/iodophor solution.</li>
</ol>
5. Post-operative care
<ol>
	<li>After completing the surgical procedure, carefully move the animal to a recovery cage with supplemental oxygen and an infra-red lamp to keep animals warm and sufficiently oxygenated during the recovery phase. Place the oxygen mask close to the rat&#39;s snout. Only keep one animal per recovery cage at any time.</li>
	<li>After the animal wakes up, carefully move it to a regular cage supplied with water and food. For the next 12 h, control the health status of the operated animal in 2 h intervals.</li>
	<li>After completing the surgical procedure, apply analgesia daily by i.p. injection of carprofen (5 mg/kg bw) for one week.</li>
	<li>To avoid bacterial infection, administer amoxicillin (500 mg/L) in the drinking water for one week postoperatively.</li>
</ol>

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The authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript.

Here, a detailed surgical technique for aortic debanding in a rat AoB model is reported that can be utilized to investigate the reversibility of PH-LHD and the cellular and molecular mechanisms that drive reverse remodeling in the pulmonary vasculature and the RV. Three weeks of aortic constriction in juvenile rats results in PH-LHD evident as increased LV pressures, LV hypertrophy, and concomitantly increased RV pressures and RV hypertrophy. Aortic debanding at week 3 post-AoB was able to unload the LV and fully reverse...

Heart failure is the leading cause of death in developed countries and is expected to increase by 25% over the next decade. Pulmonary hypertension (PH) - a pathological increase of blood pressure in the pulmonary circulation - affects approximately 70% of patients with end-stage heart failure; the World Health Organization classifies PH as pulmonary hypertension due to left heart disease (PH-LHD)1. PH-LHD is initiated by impaired systolic and/or diastolic left ventricular (LV) function that results in elevated filling pressure and passive congestion of blood into the pulmonary circulation2. Albeit initially reversible, PH-LHD gradually becomes fixed due to active pulmonary vascular remodeling in all compartments of the pulmonary circulation, i.e., arteries, capillaries, and veins3,4. Both reversible and fixed PH increase RV afterload, initially driving adaptative myocardial hypertrophy but ultimately causing RV dilatation, hypokinesis, fibrosis, and decompensation that progressively lead to RV failure1,2,5,6. As such, PH accelerates disease progression in heart failure patients and increases mortality, particularly in patients undergoing surgical treatment by implantation of left ventricular assist devices (LVAD) and/or heart transplantation7,8,9. Currently, no curative therapies exist that could reverse the process of pulmonary vascular remodeling, so fundamental mechanistic research in appropriate model systems is needed.
Importantly, clinical studies show that PH-LHD as a frequent complication in patients with aortic stenosis can improve rapidly in the early post-operative period following aortic valve replacement10. Analogously, high (&#62;3 Wood Units) pre-operative pulmonary vascular resistance (PVR) that was, however, reversible on nitroprusside was sustainably normalized after heart transplantation in a 5-year follow-up study11. Similarly, an adequate reduction of both reversible and fixed PVR and improvement of RV function in LHD patients could be realized within several months by unloading the left ventricle using implantable pulsatile and non-pulsatile ventricular assist devices12,13,14. Currently, the cellular and molecular mechanisms that drive reverse remodeling in the pulmonary circulation and RV myocardium are unclear. Yet, their understanding may provide important insight into physiological pathways that may be therapeutically exploited to reverse lung vascular and RV remodeling in PH-LHD and other forms of PH.
A suitable preclinical model that adequately replicates the pathophysiological and molecular features of PH-LHD can be used for translational studies in pressure overload-induced congestive heart failure due to surgical aortic banding (AoB) in rats4,15,16. In comparison to similar heart failure due to pressure overload in the murine model of transverse aortic constriction (TAC)17, banding of the ascending aorta above the aortic root in AoB rats does not produce hypertension in the left carotid artery as the banding site is proximal of the outflow of the left carotid artery from the aorta. As a result, AoB does not cause left-sided neuronal injury in the cortex as is characteristic for TAC18, and which may affect the study outcome. Compared to other rodent models of surgically induced PH-LHD, rat models in general, and AoB in particular, prove to be more robust, reproducible and replicate the remodeling of the pulmonary circulation characteristic for PH-LHD patients. At the same time, perioperative lethality is low19. Increased LV pressures and LV dysfunction in AoB rats induce PH-LHD development, resulting in elevated RV pressures&#160;and RV&#160;remodeling. As such, the AoB rat model has proven extremely useful in a series of previous studies by independent groups, including ourselves, to identify pathomechanisms of pulmonary vascular remodeling and test potential treatment strategies for PH-LHD4,15,20,21,22,23,24,25.
In the present study, the AoB rat model was utilized to establish a surgical procedure of aortic debanding to study mechanisms of reverse remodeling in the pulmonary vasculature and the RV. Previously, myocardial reverse remodeling models such as aortic debanding in mice26 and rats27 have been developed to investigate the cellular and molecular mechanisms regulating the regression of left ventricular hypertrophy and test potential therapeutic options to promote myocardial recovery. Moreover, a limited number of earlier studies have explored the effects of aortic debanding on PH-LHD in rats and showed that aortic debanding might reverse medial hypertrophy in pulmonary arterioles, normalize the expression of pre-pro-endothelin 1 and improve pulmonary hemodynamics27,28, providing evidence for the reversibility of PH in rats with heart failure. Here, the technical procedures of the debanding surgery are optimized and standardized, e.g., by applying a tracheotomy instead of endotracheal intubation or by using titanium clips of a defined inner diameter for aortic banding instead of polypropylene sutures with a blunt needle26,27, thus providing for better control of the surgical procedures, increased reproducibility of the model and an improved survival rate.
From a scientific perspective, the significance of the PH-LHD debanding model does not solely lie in demonstrating the reversibility of the cardiovascular and pulmonary phenotype in heart failure, but more importantly, in the identification of molecular drivers that trigger and/or sustain reverse remodeling in pulmonary arteries as promising candidates for future therapeutic targeting.

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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.

First, successful aortic debanding was confirmed by transthoracic echocardiography performed before and after the debanding procedure in AoB animals (Figure 6). To this end, the aortic arch was assessed in&#160;parasternal long axis&#160;(PLAX) B-mode view. The position of the clip on the ascending aorta in AoB animals and its absence after the Deb surgery was visualized (Figure 6A,B). Next, aortic blood flow was evaluated by pulsed-wave Doppler...

Watch this Scientific Journal Video about A Model of Reverse Vascular Remodeling in Pulmonary Hypertension Due to Left Heart Disease by Aortic Debanding in Rats at JoVE.com

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

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 ...

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2.8K Views.  German Heart Center Berlin (DHZB). 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.

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

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 Vascular Function in Patients With Chronic Kidney Disease

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this is only partially explained by traditional CVD risk factors. Vascular dysfunction is an important non-traditional risk factor, characterized by vascular endothelial dysfunction (most commonly assessed as impaired endothelium-dependent dilation [EDD]) and stiffening of the large elastic arteries. While various techniques exist to assess EDD and large elastic artery stiffness, the most commonly used are brachial artery flow-mediated dilation (FMDBA) and aortic pulse-wave velocity (aPWV), respectively. Both of these noninvasive measures of vascular dysfunction are independent predictors of future cardiovascular events in patients with and without kidney disease. Patients with CKD demonstrate both impaired FMDBA, and increased aPWV. While the exact mechanisms by which vascular dysfunction develops in CKD are incompletely understood, increased oxidative stress and a subsequent reduction in nitric oxide (NO) bioavailability are important contributors. Cellular changes in oxidative stress can be assessed by collecting vascular endothelial cells from the antecubital vein and measuring protein expression of markers of oxidative stress using immunofluorescence. We provide here a discussion of these methods to measure FMDBA, aPWV, and vascular endothelial cell protein expression.

The degree of vascular dysfunction and contributing physiological mechanisms can be assessed in patients with chronic kidney disease by measuring brachial artery flow-mediated dilation, aortic pulse-wave velocity, and vascular endothelial cell protein expression.

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this ...

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 ...

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 ...

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 ...

Left Atrial Stenosis Induced Pulmonary Venous Arterialization and Group 2 Pulmonary Hypertension in Rat

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of group 2 PH, due to mitral stenosis (MS), to facilitate the investigation of disease mechanisms and potential therapeutic strategies. We present a novel rat model of pulmonary venous congestion-induced pulmonary venous arterialization and group 2 PH caused by left atrial stenosis (LAS). LAS is achieved by constricting the left atrium using a half-closed titanium clip. After the LAS surgery, a rat model with a transmitral inflow velocity greater than or equal to 2.0 m/s on echocardiography gradually develops pulmonary venous arterialization and group 2 PH over an 8- to 10-week period. In this protocol, we provide the step-by-step procedure of how to perform the LAS surgery. The presented LAS rat model mimics MS in humans and is useful for studying the underlying molecular mechanism of pulmonary venous arterialization and for the preclinical evaluation of therapies for group 2 PH.

Left atrial stenosis (LAS) is a novel surgical technique used for studying group 2 pulmonary hypertension (PH) and mechanisms underlying pulmonary venous arterialization. Here, we present a protocol to constrict the left atrium using a titanium clip to cause pulmonary venous arterialization and moderate PH in a rat.

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of ...

The Left Pneumonectomy Combined with Monocrotaline or Sugen as a Model of Pulmonary Hypertension in Rats

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats with the additional administration of monocrotaline (MCT) or SU5416 (Sugen). We also compare these two models to other PAH models commonly used in research. In the last few years, the focus of animal PAH models has moved towards studying the mechanism of angioproliferation of plexiform lesions, in which the role of increased pulmonary blood flow is considered as an important trigger in the development of severe pulmonary vascular remodeling. One of the most promising rodent models of increased pulmonary flow is the unilateral left pneumonectomy combined with a "second hit" of MCT or Sugen. The removal of the left lung leads to increased and turbulent pulmonary blood flow and vascular remodeling. Currently, there is no detailed procedure of the pneumonectomy surgery in rats. This article details a step-by-step protocol of the pneumonectomy surgical procedure and post-operative care in male Sprague-Dawley rats. Briefly, the animal is anesthetized and the chest is opened. Once the left pulmonary artery, pulmonary vein, and bronchus are visualized, they are ligated and the left lung is removed. The chest then closed and the animal recovered. Blood is forced to circulate only on the right lung. This increased vascular pressure leads to a progressive remodeling and occlusion of small pulmonary arteries. The second hit of MCT or Sugen is used one week post-surgery to induce endothelial dysfunction. The combination of increased blood flow in the lung and endothelial dysfunction produces severe PAH. The primary limitation of this procedure is that it requires general surgical skills.

The rodent left pneumonectomy is a valuable technique in pulmonary hypertension research. Here, we present a protocol to describe the rat pneumonectomy procedure and postoperative care to ensure minimal morbidity and mortality.

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats ...

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, ...

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 ...

Use of a Percutaneous Ventricular Assist Device/Left Atrium to Femoral Artery Bypass System for Cardiogenic Shock

The left atrial to femoral artery bypass (LAFAB) system is a mechanical circulatory support (MCS) device used in cardiogenic shock (CS) that bypasses the left ventricle by draining blood from the left atrium (LA) and returning it to the systemic arterial circulation via the femoral artery. It can provide flows ranging from 2.5-5 L/min depending on the size of the cannula. Here, we discuss the mechanism of action of LAFAB, available clinical data, indications for its use in cardiogenic shock, steps of implantation, post-procedural care, and complications associated with the use of this device and their management.
We also provide a brief video of the procedural component of device therapy, including the pre-placement preparation, percutaneous placement of the device via transseptal puncture under echocardiographic guidance and the post-operative management of device parameters.

The following article describes the stepwise procedure for placement of a device (e.g., Tandemheart) in cardiogenic shock (CS) that is a percutaneous left ventricular assist device (pLVAD) and a left atrial to femoral artery bypass (LAFAB) system that bypasses and supports the left ventricle (LV) in CS.

The left atrial to femoral artery bypass (LAFAB) system is a mechanical circulatory support (MCS) device used in cardiogenic shock (CS) that bypasses the ...