Name: a model of long-term ventricular fibrillation in isolated rat hearts
Uploaded: 2023-02-17T14:15:00.000+00:00
Duration: 7 min 56 s
Description: Watch this Scientific Journal Video about A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts at JoVE.com

This work was carried out with the support of Cardiovascular Surgery, First Medical Center, Chinese PLA General Hospital and the Laboratory Animal Center, Chinese PLA General Hospital.

All the experimental procedures and protocols used in this investigation were reviewed and approved by the Animal Care and Use Committee of PLA General Hospital.
1. Preparing the Langendorff apparatus
<ol>
	<li>Prepare the Krebs-Henseleit (K-H) buffer. To prepare the K-H buffer, add the following to distilled water: 118.0 mM NaCl, 4.7 mM KCl, 1.2 mM MgSO4, 1.2 mM NaH2PO4, 1.8 mM CaCl2, 25.0 mM NaHCO3, 11.1 mM glucose, and 0.5 mM EDTA.</li>
	<li>Prepare the modified Langendorff perfusion system.
	<ol>
		<li>Continuously gas the flask containing K-H buffer with 95% O2 + 5% CO2 at a pressure of approximately 80 mmHg. Place one end of the perfusion tube in the K-H buffer, pass the middle of the perfusion tube through the water bath, and attach a blunt 20 G needle to the other end of the perfusion tube.</li>
		<li>Suspend the needle on a wire stand. Adjust the temperature of the water bath so that the temperature of the K-H buffer from the end of the perfusion system is 37.0 &#176;C &#177; 1.0 &#176;C.</li>
	</ol>
	</li>
</ol>
2. Preparing the hardware and software
<ol>
	<li>Hardware
	<ol>
		<li>Use a physiological signal recorder to digitize and record all the analog signals. Use two stainless steel needle electrodes to record a bipolar electrocardiogram (ECG), and use two stainless steel needle electrodes for electrical stimulation.</li>
		<li>Connect one end of the four electrodes to the physiological signal recorder and the other end close to the area where the heart will be positioned after attachment to the apparatus.</li>
	</ol>
	</li>
	<li>Software
	<ol>
		<li>Use the laptop software to automatically recognize, adjust, and record the bipolar ECG and hemodynamic parameters. The parameters include the left ventricular pressure difference (LVPD), the difference between the left ventricular developed pressure (LVDP) and the left ventricular end-diastolic pressure (LVEDP), and the heart rate (HR).</li>
		<li>Set the electrical stimulator parameters to 30 Hz AC, with the low voltage group receiving 2 V and the high voltage group receiving 6 V.</li>
	</ol>
	</li>
</ol>
3. Preparing the isolated heart
<ol>
	<li>Prepare the animal.
	<ol>
		<li>Anesthetize Sprague-Dawley (SD) rats with 2% isoflurane after intraperitoneal injections of 0.05 mg/kg buprenorphine and 1,000 IU/kg heparin sodium. Ensure that the rat has stopped responding to toe pinch.</li>
		<li>Transfer the rat onto a small animal surgical platform, place the rat in a supine position, and sterilize the chest with 75% ethanol.</li>
	</ol>
	</li>
	<li>Excise the heart.
	<ol>
		<li>With the rat connected to a ventilator after cervical dissection and tracheal intubation, lift the skin off the xiphoid process with toothed forceps, and make a 3 cm transverse incision in the skin with tissue scissors. Extend the skin and rib incisions to the axillae on both sides in a V-shape.</li>
		<li>Reflect the sternum cranially with tissue forceps to fully expose the heart and lungs.</li>
		<li>Isolate and bluntly dissect the thymus using two curved forceps. Clamp the thymic tissue, and deflect it laterally on both sides to expose the aorta and its branches.</li>
		<li>Use curved forceps to perform a blunt separation of the aorta and the pulmonary artery, facilitating the later use of ophthalmic scissors to remove the heart and suspend the heart once it has been removed. 
		NOTE: For those who are new to this procedure, step 3.2.4 can be omitted.</li>
		<li>Use blunt dissection to separate the brachiocephalic trunk from the surrounding tissue. Then, clamp the brachiocephalic trunk with curved forceps to facilitate the removal of the heart. Rapidly cut the aorta between the brachiocephalic trunk and the left common carotid artery. The rat dies as soon as the heart is removed.</li>
		<li>Cut off the redundant tissue, and immediately immerse the heart in a Petri dish with K-H buffer at 0-4 &#176;C to wash and pump out the residual blood. 
		NOTE: The transection of the aorta between the brachiocephalic trunk and the left common carotid artery is recommended because preserving the trunk allows for the identification of the aorta and the estimation of the depth of cannulation.</li>
	</ol>
	</li>
	<li>Suspend the heart.
	<ol>
		<li>Transfer the heart to a second Petri dish. Identify the aorta. Use two ophthalmic forceps to lift the aorta, and insert the blunt needle into the Langendorff apparatus.</li>
		<li>Adjust the aortic depth to the appropriate position. Have an assistant tie a knot with a 0 suture thread. Then, turn on the perfusion flow regulator. 
		NOTE: Take care to avoid any air bubbles entering the heart throughout the procedure. Furthermore, be aware that the time from cutting the aorta to the initial perfusion should not exceed 2 min.</li>
		<li>Insert a small modified latex balloon connected to a pressure transducer into the left atrium, and push the balloon through the mitral valve into the left ventricle. Fill the balloon with distilled water to achieve an end-diastolic pressure of 5-10 mmHg.</li>
		<li>Connect the ECG and electrical stimulation electrodes to the heart. Then, place the heart in a jacketed glass chamber to maintain an internal temperature of 37.0 &#176;C &#177; 1.0 &#176;C. 
		&#8203;NOTE: Use the following exclusion criteria: heart rate &#60;250 beats per minute; coronary flow (mL/min) &#60;10 mL/min or &#62;25 mL/min. The ECG and electrical stimulation electrode connection positions are shown in Figure 1A, and the jacketed glass chamber is shown in Figure 1B.</li>
	</ol>
	</li>
</ol>
4. Perfusing and electrically stimulating the heart (Figure 2)
<ol>
	<li>Equilibrium stage (0-30 min)
	<ol>
		<li>Start the perfusion, and maintain a temperature of approximately 37 &#176;C until the heart beats spontaneously; then, allow the heart to equilibrate for 20 min.</li>
		<li>Adjust the water bath temperature to maintain the temperature within the jacketed glass chamber at approximately 30 &#176;C. 
		NOTE: The entire cooling process should last approximately 10 min.</li>
	</ol>
	</li>
	<li>Electrical stimulation stage (30-120 min)
	<ol>
		<li>After the temperature has reached the desired level, activate the electrical stimulation switch on the laptop software. 
		NOTE: The bipolar ECG and left ventricular pressure (LVP) at the beginning of electrical stimulation are shown in Figure 3A.</li>
		<li>If the animal is part of the continuously stimulated long-term VF group, allow 90 min of electrical stimulation. If the animal is in the induced spontaneous long-term VF group, allow 5 min of electrical stimulation, then turn off the electrical stimulation, and allow 90 min for spontaneous long-term VF, as shown in Figure 3B. 
		NOTE: For hearts in the spontaneous long-term VF group that do not develop spontaneous VF within 90 min after electrical stimulation, the electrical stimulation is then turned off as they do not meet the inclusion criteria.</li>
	</ol>
	</li>
	<li>Rewarming, defibrillation, and beating stage (120-180 min)
	<ol>
		<li>After 90 min of VF, use electrodes to give 0.1 J of direct current defibrillation, as shown in Figure 3C.</li>
		<li>Simultaneously regulate the water bath temperature to allow the temperature to rise slowly within the jacketed glass chamber to about 37 &#176;C. Continue the warming process for approximately 10 min.</li>
		<li>After defibrillation, allow the heart to beat for 60 min, and then stop the beating by slow perfusion with 10% KCl at approximately 37 &#176;C. Remove the heart for further analysis. 
		&#8203;NOTE: Hearts that do not beat after defibrillation do not meet the inclusion criteria. In addition, it is important to collect the coronary effusion before cooling (at 20 min), after defibrillation (at 120 min), and at the end of the experiment (at 180 min).</li>
	</ol>
	</li>
</ol>
5. Performing the creatine kinase-MB (CK-MB) assay and histological analysis
<ol>
	<li>CK-MB assay
	<ol>
		<li>Use an automatic biochemistry analyzer and commercial CK-MB assay kit to determine the level of CK-MB in the collected coronary effusion fluid8.</li>
	</ol>
	</li>
	<li>Histological analysis
	<ol>
		<li>Fix the heart in buffered 10% formalin, dehydrate the heart, and embed it in paraffin.</li>
		<li>Use a microtome to cut the paraffin-embedded tissue into 5 &#181;m sections; then, mount the sections on glass slides, and stain with hematoxylin and eosin9.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

This protocol establishes an animal model of long-term VF in isolated rat hearts that has not been previously reported. Additionally, different electrical stimulation conditions were compared in this study. This study provides a model for studies related to ventricular fibrillation arrest during cardiac surgery.
The success rate of the model is a very important indicator that is related to personnel, time, and economic costs. In VF models, the success rate includes whether VF can be induced in...

Cardiac surgery is usually performed via thoracotomy, with blocking of the aorta and perfusion with a cardioplegic solution to arrest the heart. Repeat cardiac surgery can be more challenging than the initial surgery, with higher complication and mortality rates1,2,3. Furthermore, the conventional median sternotomy approach may cause damage to the bridge vessels behind the sternum, the ascending aorta, the right ventricle, and other important structures. Extensive bleeding due to the separation of connective tissue, sternal wound infection, and sternal osteomyelitis due to sternotomy are all possible complications. Extensive dissection increases the risk of lesions and hemorrhage in vital cardiac structures.
With the development of minimally invasive cardiac surgery, incisions have become smaller, and cardiac arrest is sometimes difficult to achieve. Repeat cardiac surgery under ventricular fibrillation (VF)4,5 is safe, feasible, and may provide better myocardial protection. Therefore, this protocol introduces the method of VF cardiac arrest in surgery with minimally invasive extracorporeal circulation. The heart loses effective contraction during VF, and, thus, there is no need to suture and block the ascending aorta during surgery, which simplifies the procedure. However, even if the heart is continuously perfused, long-term VF may still be harmful to the heart.
As this method becomes more widely used, the question of how to protect the heart during VF becomes increasingly relevant. This will require extensive and in-depth studies using animal models of long-term VF. In the past, research in this field has mostly used large animals6,7 and has required cooperation between surgeons, anesthesiologists, perfusionists, and other researchers. These studies took too long, the sample sizes were often small, and the studies generally focused on cardiac function and less on mechanistic and molecular assessments. To date, no study has reported a detailed protocol to establish a long-term VF model.
This protocol, thus, provides the details needed to develop a long-term VF rat model using Langendorff apparatus. The protocol is simple, economical, repeatable, and stable.

<table><tbody><tr><td>0 Non-absorbable suture</td><td>Ethicon, Inc.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>95% O&lt;sub&gt;2&lt;/sub&gt; + 5% CO&lt;sub&gt;2&lt;/sub&gt;</td><td>Beijing BeiYang United Gas Co., Ltd.&amp;nbsp;</td><td></td><td>K-H buffer</td></tr><tr><td>AcqKnowledge software</td><td>BIOPAC Systems Inc.</td><td>Version 4.2.1</td><td>Software</td></tr><tr><td>Automatic biochemistry analyzer</td><td>Rayto Life and Analytical Sciences Co., Ltd.</td><td>Chemray 800</td><td>CK-MB assay</td></tr><tr><td>BIOPAC research systems</td><td>BIOPAC Systems Inc.</td><td>MP150</td><td>Hardware</td></tr><tr><td>Blunt needle (20 G, TWLB)</td><td>Tianjin Hanaco MEDICAL Co., Ltd.</td><td>H-113AP-S</td><td>Modified Langendorff perfusion system</td></tr><tr><td>Calcium chloride</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>10005861</td><td>K-H buffer</td></tr><tr><td>CK-MB assay kits&amp;nbsp;</td><td>Changchun Huili Biotech Co., Ltd.</td><td>C060</td><td>CK-MB assay</td></tr><tr><td>Curved forcep</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>EDTA</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>10009717</td><td>K-H buffer</td></tr><tr><td>Electrical stimulator</td><td>BIOPAC Systems Inc.</td><td>STEMISOC</td><td>Hardware</td></tr><tr><td>Filter</td><td>Tianjin Hanaco MEDICAL Co., Ltd.</td><td>H-113AP-S</td><td></td></tr><tr><td>Glucose</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>63005518</td><td>K-H buffer</td></tr><tr><td>Heparin sodium</td><td>Tianjin Biochem Pharmaceutical Co., Ltd.</td><td>H120200505</td><td>Preparation of the isolated heart</td></tr><tr><td>Isoflurane</td><td>RWD Life Science Co.,LTD</td><td>21082201</td><td>Preparation of the isolated heart</td></tr><tr><td>Magnesium sulfate</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>20025118</td><td>K-H buffer</td></tr><tr><td>Needle electrodes</td><td>BIOPAC Systems Inc.</td><td>EL452</td><td>Hardware</td></tr><tr><td>Ophthalmic clamp</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>Ophthalmic forceps</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>Ophthalmic scissors</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>Perfusion tube</td><td>Tianjin Hanaco MEDICAL Co., Ltd.</td><td>H-113AP-S</td><td>Modified Langendorff perfusion system</td></tr><tr><td>Potassium chloride</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>10016318</td><td>K-H buffer</td></tr><tr><td>Sodium bicarbonate</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>10018960</td><td>K-H buffer</td></tr><tr><td>Sodium chloride</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>10019318</td><td>K-H buffer</td></tr><tr><td>Sodium dihydrogen phosphate dihydrate</td><td>Sinopharm Chemical Reagent Co.,Ltd</td><td>20040718</td><td>K-H buffer</td></tr><tr><td>Sprague-Dawley (SD) rats</td><td>SPF (Beijing) biotechnology Co., Ltd.</td><td>Male, 300-350g</td><td>Preparation of the isolated heart</td></tr><tr><td>Thermometer</td><td>Jiangsu Jingchuang Electronics Co., Ltd.</td><td>GSP-6</td><td>Modified Langendorff perfusion system</td></tr><tr><td>Tissueforceps</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>Tissue scissors</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>Toothed forceps</td><td>Shanghai Medical Instrument (Group) Co., Ltd.</td><td></td><td>Preparation of the isolated heart</td></tr><tr><td>Ventilator</td><td>Chengdu Instrument Factory</td><td>DKX-150</td><td>Preparation of the isolated heart</td></tr><tr><td>Water bath1</td><td>Ningbo Scientz Biotechnology Co.,Ltd.</td><td>SC-15</td><td>Modified Langendorff perfusion system</td></tr><tr><td>Water bath2</td><td>Shanghai Yiheng Technology Instrument Co., Ltd.</td><td>DK-8D</td><td>Modified Langendorff perfusion system</td></tr></tbody></table>

a model of long-term ventricular fibrillation in isolated rat hearts

Ventricular fibrillation (VF) is a fatal arrhythmia with a high incidence in cardiac patients, but VF arrest under perfusion is a neglected method of intraoperative arrest in the field of cardiac surgery. With recent advances in cardiac surgery, the demand for prolonged VF studies under perfusion has increased. However, the field lacks simple, reliable, and reproducible animal models of chronic ventricular fibrillation. This protocol induces long-term VF through alternating current (AC) electrical stimulation of the epicardium. Different conditions were used to induce VF, including continuous stimulation with a low or high voltage to induce long-term VF and stimulation for 5 min with a low or high voltage to induce spontaneous long-term VF. The success rates of the different conditions, as well as the rates of myocardial injury and recovery of cardiac function, were compared. The results showed that continuous low-voltage stimulation induced long-term VF and that 5 min of low-voltage stimulation induced spontaneous long-term VF with mild myocardial injury and a high rate of recovery of cardiac function. However, the low-voltage, continuously stimulated long-term VF model had a higher success rate. High-voltage stimulation provided a higher rate of VF induction but showed a low defibrillation success rate, poor recovery of cardiac function, and severe myocardial injury. On the basis of these results, continuous low-voltage epicardial AC stimulation is recommended for its high success rate, stability, reliability, reproducibility, low impact on cardiac function, and mild myocardial injury.

A total of 57 rats were used in the experiments, of which 30 fulfilled the inclusion criteria. The included animals were divided into five groups, with six animals in each group: the control group (Group C), the low-voltage continuously stimulated long-term VF group (Group LC), the high-voltage continuously stimulated long-term VF group (Group HC), the low voltage-induced spontaneous long-term VF group (Group LI), and the high voltage-induced spontaneous long-term VF group (Group HI). The experimental process for each gr...

Watch this Scientific Journal Video about A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts at JoVE.com

A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

This protocol presents a model of long-term ventricular fibrillation in rat hearts induced by continuous stimulation with low-voltage alternating current. This model has a high success rate, is stable, reliable, and reproducible, has a low impact on cardiac function, and causes only mild myocardial injury.

Ventricular fibrillation (VF) is a fatal arrhythmia with a high incidence in cardiac patients, but VF arrest under perfusion is a neglected method of ...

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859 Views.  Chinese PLA General Hospital. This protocol presents a model of long-term ventricular fibrillation in rat hearts induced by continuous stimulation with low-voltage alternating current. This model has a high success rate, is stable, reliable, and reproducible, has a low impact on cardiac function, and causes only mild myocardial injury.

Video: A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

Acute Myocardial Infarction in Rats

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular diseases. Animal models that mimic human cardiac disease, such as myocardial infarction (MI) and ischemia-reperfusion (IR) that induces heart failure as well as pressure-overload (transverse aortic constriction) that induces cardiac hypertrophy and heart failure (Goldman and Tarnavski), are useful models to study cardiovascular disease. In particular, myocardial ischemia (MI) is a leading cause for cardiovascular morbidity and mortality despite controlling certain risk factors such as arteriosclerosis and treatments via surgical intervention (Thygesen). Furthermore, an acute loss of the myocardium following myocardial ischemia (MI) results in increased loading conditions that induces ventricular remodeling of the infarcted border zone and the remote non-infarcted myocardium. Myocyte apoptosis, necrosis and the resultant increased hemodynamic load activate multiple biochemical intracellular signaling that initiates LV dilatation, hypertrophy, ventricular shape distortion, and collagen scar formation. This pathological remodeling and failure to normalize the increased wall stresses results in progressive dilatation, recruitment of the border zone myocardium into the scar, and eventually deterioration in myocardial contractile function (i.e. heart failure). The progression of LV dysfunction and heart failure in rats is similar to that observed in patients who sustain a large myocardial infarction, survive and subsequently develops heart failure (Goldman). The acute myocardial infarction (AMI) model in rats has been used to mimic human cardiovascular disease; specifically used to study cardiac signaling mechanisms associated with heart failure as well as to assess the contribution of therapeutic strategies for the treatment of heart failure. The method described in this report is the rat model of acute myocardial infarction (AMI). This model is also referred to as an acute ischemic cardiomyopathy or ischemia followed by reperfusion (IR); which is induced by an acute 30-minute period of ischemia by ligation of the left anterior descending artery (LAD) followed by reperfusion of the tissue by releasing the LAD ligation (Vasilyev and McConnell). This protocol will focus on assessment of the infarct size and the area-at-risk (AAR) by Evan's blue dye and triphenyl tetrazolium chloride (TTC) following 4-hours of reperfusion; additional comments toward the evaluation of cardiac function and remodeling by modifying the duration of reperfusion, is also presented. Overall, this AMI rat animal model is useful for studying the consequence of a myocardial infarction on cardiac pathophysiological and physiological function.

The rat model of acute myocardial infarction (AMI) is useful to study the consequence of a MI on cardiac pathophysiological and physiological function.

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular ...

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance seen in clinical practice and its prevalence is expected to increase in the coming years.3 Increased intra-atrial pressure and dilatation have been long recognized to lead to AF,1,4 which highlights the relevance of using animal models and stretch to study AF dynamics. Understanding the mechanisms underlying AF requires visualization of the cardiac electrical waves with high spatial and temporal resolution. While high-temporal resolution can be achieved by conventional electrical mapping traditionally used in human electrophysiological studies, the small number of intra-atrial electrodes that can be used simultaneously limits the spatial resolution and precludes any detailed tracking of the electrical waves during the arrhythmia. The introduction of optical mapping in the early 90's enabled wide-field characterization of fibrillatory activity together with sub-millimeter spatial resolution in animal models5,6 and led to the identification of rapidly spinning electrical wave patterns (rotors) as the sources of the fibrillatory activity that may occur in the ventricles or the atria.7-9 Using combined time- and frequency-domain analyses of optical mapping it is possible to demonstrate discrete sites of high frequency periodic activity during AF, along with frequency gradients between left and right atrium. The region with fastest rotors activates at the highest frequency and drives the overall arrhythmia.10,11 The waves emanating from such rotor interact with either functional or anatomic obstacles in their path, resulting in the phenomenon of fibrillatory conduction.12 Mapping the endocardial surface of the posterior left atrium (PLA) allows the tracking of AF wave dynamics in the region with the highest rotor frequency. Importantly, the PLA is the region where intracavitary catheter-based ablative procedures are most successful terminating AF in patients,13 which underscores the relevance of studying AF dynamics from the interior of the left atrium. Here we describe a sheep model of acute stretch-induced AF, which resembles some of the characteristics of human paroxysmal AF. Epicardial mapping on the left atrium is complemented with endocardial mapping of the PLA using a dual-channel rigid borescope c-mounted to a CCD camera, which represents the most direct approach to visualize the patterns of activation in the most relevant region for AF maintenance.

This report provides a detailed description of the methodology and results of simultaneous endocardial and epicardial optical mapping of electrical excitation in the intact left atrium of a Langendorff-perfused sheep heart during stretch-induced atrial fibrillation.

 Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance ...

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes &#8211; but is not limited to &#8211; hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.

This article describes a rat model of electrically-induced ventricular fibrillation and resuscitation by chest compression, ventilation, and delivery of electrical shocks that simulates an episode of sudden cardiac arrest and conventional cardiopulmonary resuscitation. The model enables gathering insights on the pathophysiology of cardiac arrest and exploration of new resuscitation strategies.

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic ...

Murine Isolated Heart Model of Myocardial Stunning Associated with Cardioplegic Arrest

The following protocol is of use to evaluate impaired cardiac function or myocardial stunning following moderate ischemic insults. The technique is useful for modeling ischemic injury associated with numerous clinically relevant phenomenon including cardiac surgery with cardioplegic arrest and cardiopulmonary bypass, off-pump CABG, transplant, angina, brief ischemia, etc. The protocol presents a general method to model hypothermic hyperkalemic cardioplegic arrest and reperfusion in rodent hearts focusing on measurement of myocardial contractile function. In brief, a mouse heart is perfused in langendorff mode, instrumented with an intraventricular balloon, and baseline cardiac functional parameters are recorded. Following stabilization, the heart is then subject to brief infusion of a cardioprotective hypothermic cardioplegia solution to initiate diastolic arrest. Cardioplegia is delivered intermittently over 2 hr. The heart is then reperfused and warmed to normothermic temperatures and recovery of myocardial function is monitored. Use of this protocol results in reliable depressed cardiac contractile function free from gross myocardial tissue damage in rodents.

The goal of this protocol to assess myocardial stunning following ischemic cardioplegic arrest in rodents.

The following protocol is of use to evaluate impaired cardiac function or myocardial stunning following moderate ischemic insults. The technique is useful ...

Isolation of Atrial Cardiomyocytes from a Rat Model of Metabolic Syndrome-related Heart Failure with Preserved Ejection Fraction

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of metabolic syndrome (MetS)-related heart failure with preserved ejection fraction (HFpEF). The prevalence of MetS-related HFpEF is rising, and atrial cardiomyopathies associated with atrial remodeling and atrial fibrillation are clinically highly relevant as atrial remodeling is an independent predictor of mortality. Studies with isolated single-cell cardiomyocytes are frequently used to corroborate and complement in vivo findings. Circulatory vessel rarefication and interstitial tissue fibrosis pose a potentially limiting factor for the successful single-cell isolation of ACMs from animal models of this disease.
We have addressed this issue by employing a device capable of manually regulating the intraluminal pressure of cardiac cavities during the isolation procedure, substantially increasing the yield of morphologically and functionally intact ACMs. The acquired cells can be used in a variety of different experiments, such as cell culture and functional Calcium imaging (i.e., excitation-contraction-coupling).
We provide the researcher with a step-by-step protocol, a list of optimized solutions, thorough instructions to prepare the necessary equipment, and a comprehensive troubleshooting guide. While the initial implementation of the procedure might be rather difficult, a successful adaptation will allow the reader to perform state-of-the-art ACM isolations in a rat model of MetS-related HFpEF for a broad spectrum of experiments.

Here, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes from a rat model of metabolic syndrome-related heart failure with preserved ejection fraction. A manual regulation of intraluminal pressure of cardiac cavities is implemented to yield functionally intact myocytes suitable for excitation-contraction-coupling studies.

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of ...

Standardized Model of Ventricular Fibrillation and Advanced Cardiac Life Support in Swine

Cardiopulmonary resuscitation after cardiac arrest, independent of its origin, is a regularly encountered medical emergency in hospitals as well as preclinical settings. Prospective randomized trials in human subjects are difficult to design and ethically ambiguous, which results in a lack of evidence-based therapies. The model presented in this report represents one of the most common causes of cardiac arrests, ventricular fibrillation, in a standardized setting in a large animal model. This allows for reproducible observations and various therapeutic interventions under clinically accurate conditions, hence facilitating the generation of better evidence and eventually the potential for improved medical treatment.

Cardiopulmonary resuscitation and defibrillation are the only effective therapeutic options during cardiac arrest caused by ventricular fibrillation. This model presents a standardized regimen to induce, assess, and treat this physiological state in a porcine model, thus providing a clinical approach with various opportunities for data collection and analysis.

Cardiopulmonary resuscitation after cardiac arrest, independent of its origin, is a regularly encountered medical emergency in hospitals as well as ...

A New Model of Heart Failure Post-Myocardial Infarction in the Rat

Ligation of the left anterior descending (LAD) coronary artery has been widely used to establish the rat model of heart failure (HF) post myocardial infarction (MI). However, the disadvantages of this model include high mortality rate after ligation and larger variations both in the infarct size and the degree of impaired cardiac function. In addition, a ventilator or exteriorization of the heart is indispensable for the previous models, which complicates the procedure during the ligation. In this study, we developed a reliable and reproducible model without the ventilator or exteriorization of the heart by ligating the LAD coronary artery. Four weeks after the procedure, we found that the serum concentrations of CK-MB, NT-proBNP, and Renin, which were used to assist diagnoses of MI and HF, were significantly higher in the MI group compared to the sham group. In contrast, the value of left ventricle ejection fraction (LVEF) in the MI group was obviously less than in the sham group. Furthermore, the infarct size and cardiac fibrosis area were individually confirmed and quantitatively analyzed by TTC staining and Masson's trichrome staining. Smaller variations were found in either infarct size or fibrosis area in the MI group, which helped to develop a reliable and reproducible model of HF post-MI. This new model of HF post-MI in the rat is vital for studying the potential mechanisms of MI and HF. This new method can be used to develop the new drug for treatment of MI and HF in rats by using pharmacological strategies.

We successfully developed a reliable and reproducible model of heart failure post-myocardial infarction in the rat without ventilation or exteriorization of the heart. This simplifies the procedure and benefits the further studies about the potential mechanisms behind the heart failure.

Ligation of the left anterior descending (LAD) coronary artery has been widely used to establish the rat model of heart failure (HF) post myocardial ...

Improved Rodent Model of Myocardial Ischemia and Reperfusion Injury

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence suggests that thrombolytic therapy or primary percutaneous coronary intervention (PPCI) does not prevent reperfusion injury. There is still no ideal animal model for MIRI. This study aims to improve the MIRI model in rats to make surgery easier and more feasible. A unique method for establishing MIRI is developed by using a soft tube during a key step of the ischemic period. To explore this method, thirty rats were randomly divided into three groups: sham group (n = 10); experimental model group (n = 10); and existing model group (n = 10). Findings of triphenyltetrazolium chloride staining, electrocardiography, and percent survival are compared to determine the accuracies and survival rates of the operations. Based on the study results, it has been concluded that the improved surgery method is associated with a higher survival rate, elevated ST-T segment, and larger infarct size, which is expected to mimic the pathology of MIRI better.

Myocardial ischemia-reperfusion model of rat heart is improved by using a self-made retractor, polyvinyl chloride tube, and a unique knotting method. Electrocardiogram, triphenyltetrazolium chloride and histological staining, and percent survival analysis results showed that the improved model group has higher success and survival rates than the already existing model group.

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence ...

Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats

Animal studies have brought important insights into our understanding regarding atrial fibrillation (AF) pathophysiology and therapeutic management. Reentry, one of the main mechanisms involved in AF pathogenesis, requires a certain mass of myocardial tissue in order to occur. Due to the small size of the atria, rodents have long been considered 'resistant' to AF. Although spontaneous AF has been shown to occur in rats, long-term follow-up (up to 50 weeks) is required for the arrhythmia to occur in those models. The present work describes an experimental protocol of transesophageal atrial burst pacing for rapid and efficient induction of AF in rats. The protocol can be successfully used in rats with healthy or remodeled hearts, in the presence of a wide variety of risk factors, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of novel prophylactic and/or therapeutic strategies.

The present work describes an experimental protocol of transesophageal atrial burst pacing for efficient induction of atrial fibrillation (AF) in rats. The protocol can be used in rats with healthy or remodeled hearts, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of new therapeutic strategies.

Animal studies have brought important insights into our understanding regarding atrial fibrillation (AF) pathophysiology and therapeutic management. ...

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

It is now well recognized that heart failure (HF) patients with left bundle branch block (LBBB) derive substantial clinical benefits from cardiac resynchronization therapy (CRT), and LBBB has become one of the important predictors for CRT response. The conventional tachypacing-induced HF model has several major limitations, including absence of stable LBBB and rapid reversal of left ventricular (LV) dysfunction after cessation of pacing. Hence, it is essential to establish an optimal model of chronic HF with isolated LBBB for studying CRT benefits. In the present study, a canine model of asynchronous HF induced by left bundle branch (LBB) ablation and 4 weeks of rapid right ventricular (RV) pacing is established. The RV and right atrial (RA) pacing electrodes via the jugular vein approach, together with an epicardial LV pacing electrode, were implanted for CRT performance. Presented here are the detailed protocols of radiofrequency (RF) catheter ablation, pacing leads implantation, and rapid pacing strategy. Intracardiac and surface electrograms during operation were also provided for a better understanding of LBB ablation. Two-dimensional speckle tracking imaging and aortic velocity time integral (aVTI) were acquired to validate the chronic stable HF model with LV asynchrony and CRT benefits. By coordinating ventricular activation and contraction, CRT uniformed the LV mechanical work and restored LV pump function, which was followed by reversal of LV dilation. Moreover, the histopathological study revealed a significant restoration of cardiomyocyte diameter and collagen volume fraction (CVF) after CRT performance, indicating a histologic and cellular reverse remodeling elicited by CRT. In this report, we described a feasible and valid method to develop a chronic asynchronous HF model, which was suitable for studying structural and biologic reverse remodeling following CRT.

The establishment of a chronic asynchronous heart failure (HF) model by rapid pacing combined with left bundle branch ablation is presented. Two-dimensional speckle tracking imaging and aortic velocity time integral are applied to validate this stable HF model with left ventricular asynchrony and the benefits of cardiac resynchronization therapy.