Name: improvement of a closed chest porcine myocardial infarction model by standardization of tissue and blood sampling procedures
Uploaded: 2018-03-12T14:30:00
Description: Watch this Scientific Journal Video about Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures at JoVE.com

The authors wish to acknowledge Professor Christian Heinis for providing the FXIIa inhibitor and the respective control. We also gratefully acknowledge Olgica Beslac, Dr. Daniel Mettler and Kay Nettelbeck from the Experimental Surgery Unit, Department for Biomedical Research, University of Bern for technical support. Celine Guillod and Matthias Rausch from the Department for Diagnostic, Interventional and Pediatric Radiology, Bern University Hospital, Inselspital provided support with the X-ray equipment and techniques.This project was funded by the Swiss National Science Foundation, project no. 320030_156193.&#160;We also would like to thank Mr. Reto Haenni from communication and marketing, Bern University Hospital, Inselspital for video recording our experiment.

1. Animals:
All animals were treated according to the guidelines of the Swiss national laws. The study was approved by the local animal experimentation committee of the Canton of Bern (permission no. BE 25/16).
Use large white pigs of both sexes (~30 &#177;&#160;5 kg). Divide the animals blindly into two groups, one group receiving a bicyclic (80 kDa protease) inhibitor of FXIIa or treatment of choice and the other an inactive control.
2. Sur...

<ol>
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L., Granger, D. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathophysiology+of+ischaemia-reperfusion+injury.">Pathophysiology of ischaemia-reperfusion injury.</a> J Pathol. 190, 255-266 (2000).</li><li>P&#233;rez de Prado, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Closed-chest+experimental+porcine+model+of+acute+myocardial+infarction-reperfusion.">Closed-chest experimental porcine model of acute myocardial infarction-reperfusion.</a> J Pharmacol Toxicol Methods. 60, 301-306 (2009).</li><li>Lown, B., Levine, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+carotid+sinus.+Clinical+value+of+its+stimulation.">The carotid sinus. 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Myocardial I/R injury has a significant effect on the final infarct size which is directly translated into the patient&#39;s prognosis after acute myocardial infarction3. Understanding the pathophysiology of myocardial I/R injury is the first step to reduce or prevent it. Myocardial I/R injury is an acute condition that occurs directly after reperfusion of the occluded vessels. I/R injury leads to activation of the innate immune response and cellular damage occurs at the site of reperfusion and th...

Ischemic heart disease, in particular acute myocardial infarction (MI), is the main cause of death in developed countries 1. Today, the standard treatment of MI is percutaneous coronary intervention (PCI), the balloon catheter treatment. One of the critical factors that affects quality of life and prognosis of patients after PCI-treated acute MI is the infarction size. The reduction of the size can have a great impact on patient survival and prognosis 2. Myocardial ischemia/reperfusion (I/R) injury has a significant influence on the infarction size so one of the main aims in cardiovascular research is to prevent or reduce myocardial I/R injury 3. The exact mechanisms of I/R injury are still under investigation 4. Activation of the plasma cascades and endothelial cells are hallmarks of I/R injury 5. Activation of the coagulation system is clearly involved 6,7. Recently, the role of FXII, as an early upstream peptide involved in contact phase activation of the coagulation cascade, has been shown in a FXII knock out rat model of cerebral I/R injury 8. Validation of these results in a porcine model is an important step into clinical translation. Therefore, we are testing a novel bicyclic (80 kDa protease) FXIIa inhibitor in the context of myocardial I/R injury in a pilot study.
Animal models, which mimic the clinical situation of acute MI and PCI treatments, are essential to improve our understanding of the pathophysiology of myocardial I/R injury and to test novel treatment options. Pigs represent a good animal model for clinical myocardial I/R injury. This is not only because their hearts are very similar to human hearts with respect to anatomy and coronary circulation, but they also show similar pathophysiological responses to myocardial ischemia and reperfusion 9,10. Other models such as rats and mice do not fulfill these criteria and show considerable differences when compared to human hearts 11,12, whereas dogs for example, have many more collateral coronary vessels as compared with humans 13.
The porcine acute myocardial infarction model has been widely used in cardiovascular research to investigate ischemic heart disease including myocardial I/R injury 14,15,16,17. The latter is an inflammatory condition, because of which minimizing the inflammatory reaction related to sternotomy or thoracotomy used in open-chest surgery is essential. The closed chest model using a clinical C-arm angiography setting overcomes this problem. Furthermore, one of the most important points is that our protocol provides an accurate distinction between ischemic (area at risk, AAR) and non-ischemic areas of the left ventricle (area not at risk, ANR) so that the infarct size (necrotic ischemic tissue, NIT) can be accurately determined. Our aim for this paper is to clearly define a reproducible methodology of a porcine myocardial I/R injury model, in particular with respect to myocardial tissue sampling, which will allow for a more precise analysis of the molecular mechanisms of I/R injury and a clearer picture of the effects of novel drug treatments.

<table>
	<tbody>
		<tr>
			<td>ABL 90 Flex, blood gas analyser</td>
			<td>Radiometer</td>
			<td>-</td>
			<td>Blood gas analysis (BGA)</td>
		</tr>
		<tr>
			<td>ACT Plus</td>
			<td>Medtronic</td>
			<td>-</td>
			<td>Activated clotting time</td>
		</tr>
		<tr>
			<td>Atropin</td>
			<td>Sintetica</td>
			<td>-</td>
			<td>Atropinum Sulfas, 0,5mg/ml</td>
		</tr>
		<tr>
			<td>Balance (20-500 Kg)</td>
			<td>NAGATA Scale, Tiwan</td>
			<td>HTB/HTR</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Balance (21-4200 g)</td>
			<td>Mettler toledo, Switzerland</td>
			<td>MS4002SDR</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Blood collection tubes: EDTA, citrate and serum</td>
			<td>S-Monovette, Nuembrecht, Germany</td>
			<td>05.1167.001, 
			05.1071.001 
			and 
			05.1557.001 respectively</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>BV Pulsera mobile C-arm</td>
			<td>Philips</td>
			<td>-</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Labcare, UK</td>
			<td>ALC PK120R</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Defibrillator Lifepak 12</td>
			<td>Medtronic</td>
			<td>-</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Dextran from Leuconostoc mesenteroides</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>D3759</td>
			<td>Average M.wt 48000-90000</td>
		</tr>
		<tr>
			<td>Digital single lens reflex camera</td>
			<td>Sony, Thailand</td>
			<td>DSLR-A500/A550</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Dissecting forceps</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>EMPIRA RX PCI dilatation catheter</td>
			<td>Cordis, Johnson&#38;Johnson, USA</td>
			<td>85R15300S</td>
			<td>Diameter 3 mm, length 15 mm, Alternative products can be used</td>
		</tr>
		<tr>
			<td>EMPIRA RX PCI dilatation catheter</td>
			<td>Cordis, Johnson&#38;Johnson, USA</td>
			<td>85R15350S</td>
			<td>Diameter 3.5 mm, length 15 mm, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Evans Blue</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>E2129</td>
			<td>Toxic</td>
		</tr>
		<tr>
			<td>Fabius GS premium respirator</td>
			<td>Dr&#228;ger, L&#252;beck, Germany</td>
			<td>-</td>
			<td>Anesthesia work station, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Fentanyl</td>
			<td>Inselspital ISPI</td>
			<td>-</td>
			<td>Fentanyl 2500mcg/50ml</td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Pathology Institute, Bern University</td>
			<td>SI148701</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>FXIIa inhibitor</td>
			<td>Provided by Prof. Christian Heinis&#39; laboratory in EPFL</td>
			<td></td>
			<td>Novel bicyclic peptide</td>
		</tr>
		<tr>
			<td>Galeo, coronary guidewire</td>
			<td>Biotronik, Germany</td>
			<td>125497</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Guidance catheter</td>
			<td>Boston Scientific, Florida, USA</td>
			<td>34356-06</td>
			<td>6F (100 cm, EB3.75). Alternative products can be used</td>
		</tr>
		<tr>
			<td>Heparin Sodium</td>
			<td>Drossapharm, Basel, Switzerland</td>
			<td>-</td>
			<td>Liquemin, 25000 U.I./5 ml</td>
		</tr>
		<tr>
			<td>High end electrosurgery</td>
			<td>BOWA, Germany</td>
			<td>ARC 400</td>
			<td>Electrical source for blood suction. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Hydro-Guardmini breathing filter</td>
			<td>Intersurgical, Lithuania</td>
			<td>1745000</td>
			<td>Filters</td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>National Institute of Health, USA</td>
			<td>1.47v</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Inflation device, Atrion QL2530</td>
			<td>Atrion medical product, Alabama, USA</td>
			<td>96402</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>IntelliVue MP 70</td>
			<td>Philips, Boeblingen, Germany</td>
			<td>-</td>
			<td>Monitor (ECG, heart rate, blood presure and body temperature). Alternative products can be used</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sintetica SA</td>
			<td>-</td>
			<td>Potassium chloride 15%</td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>Vetoquinol</td>
			<td>-</td>
			<td>Narketan, 1ml/100mg</td>
		</tr>
		<tr>
			<td>LR-ACT</td>
			<td>Medtronic</td>
			<td>402-01</td>
			<td>ACT special syringes</td>
		</tr>
		<tr>
			<td>Midazolam</td>
			<td>Roche</td>
			<td>-</td>
			<td>Dormicum, 5mg/ml</td>
		</tr>
		<tr>
			<td>Monopolar scalpel</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Needle holder</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>High resolution camera, PathStand Macro Imaging Stand for Grossing</td>
			<td>Spotimaging, USA</td>
			<td></td>
			<td>1080 p HD resolution. Alternative products can be used</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>In-house preparation</td>
			<td>-</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Peripheral venous cannula, 18 G</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>PowerLab 4/35 data acquisition system</td>
			<td>Adinstruments, Spechbach, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotamax120T</td>
			<td>Heidolph, Germany</td>
			<td>544-41200-00</td>
			<td>Shaker. Alternative can be used</td>
		</tr>
		<tr>
			<td>R&#252;schelit-Super Safety Clear Tube</td>
			<td>Teleflex, Dublin, Irland</td>
			<td>112480</td>
			<td>Air way tubing, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Safe Pico Aspirator Syringes</td>
			<td>Radiometer</td>
			<td>956-622</td>
			<td>BGA special syringes</td>
		</tr>
		<tr>
			<td>Saline</td>
			<td>Sintetica Bioren</td>
			<td>-</td>
			<td>NaCl 0,9%. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Sevorane 1.5%</td>
			<td>AbbVie AG</td>
			<td>-</td>
			<td>Sevorane 250ml 100%</td>
		</tr>
		<tr>
			<td>Sheath</td>
			<td>Cordis, Johnson&#38;Johnson, USA</td>
			<td>504-607 A</td>
			<td>AVANTI + / 7 F, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Space infusion pump</td>
			<td>B.Braun Medical AG, Germany</td>
			<td>-</td>
			<td>For infusion of fentanyl. Alternative products can be used</td>
		</tr>
		<tr>
			<td>SPR-350 (Millar catheter)</td>
			<td>Adinstruments, Texas, USA</td>
			<td>840-8166</td>
			<td>MIKRO-TIP, 5F, 120 cm</td>
		</tr>
		<tr>
			<td>Sternotomy saw</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Sutures</td>
			<td>ETHICON, Johnson&#38;Johnson, USA</td>
			<td>Y3110H</td>
			<td>Monocryl 3-0 SH-1 Plus. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Syringes (20, 10 and 5 mL)</td>
			<td>CODAN,Baar, Switzerland</td>
			<td>62.7602, 
			62.6616, 
			62.5607 
			respectively</td>
			<td>Used to inject anesthetic materials intramuscularly or directly into the central venous line. Also to inject heparin or FXIIa or the respective control. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Thorax spreader</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Tissue-tek</td>
			<td>SAKURA, Netherlands</td>
			<td>4583</td>
			<td>O.C.T. compound</td>
		</tr>
		<tr>
			<td>Vascular forceps</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Xenetix 300 contrast media</td>
			<td>Guerbet, Z&#252;rich, Switzerland</td>
			<td>-</td>
			<td>Lobitridol, 300 mg iodide/ml</td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>Vetoquinol</td>
			<td>-</td>
			<td>Xylapan, 20mg/1 mL</td>
		</tr>
		<tr>
			<td>2,3,5-Triphenyltetrazolium choride</td>
			<td>Sigma-Aldrich, Austria</td>
			<td>T8877</td>
			<td></td>
		</tr>
		<tr>
			<td>500 &#956;L tubes (eppendorf)</td>
			<td>Trefflab, Switzerland</td>
			<td>96.08185.9.03</td>
			<td>Alternative products can be used</td>
		</tr>
	</tbody>
</table>

improvement of a closed chest porcine myocardial infarction model by standardization of tissue and blood sampling procedures

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved drug to prevent or reduce myocardial I/R injury. The study and understanding of the pathophysiological mechanisms of myocardial I/R injury is essential to develop successful treatments. Large animal experiments are an important step in translational methods. The porcine model of acute myocardial infarction has been established and described by ourselves and others. We aimed to further improve the value of the model by focusing in detail on the sampling techniques for use in future experiments. Furthermore, we emphasize small but important steps that can affect the quality of the final results. To mimic the clinical situation of myocardial I/R injury, a percutaneous coronary intervention (PCI) catheter was inserted into the left anterior descending coronary artery (LAD) of an anesthetized pig. &#176;&#176;&#176;This model mimics acute myocardial infarction and PCI treatment in humans with the possibility of accurately determining the area at risk as well as the necrotic- and viable ischemic tissue. Here the model was used to investigate the effect of a bicyclic peptide inhibitor of FXIIa. The model can also be modified to allow longer reperfusion times to study later effects of myocardial infarction.

One animal died prematurely before administration of FXIIa inhibitor or control peptide due to a technical error (sudden drop of blood pressure during ischemia time, before addition of test substance). One animal was excluded from the FXIIa inhibitor group because no ischemia/reperfusion injury was observed due to abnormal anatomy of the left anterior descending artery (LAD). A large part of the left ventricle, including the apex, was perfused by the circumflex artery in this animal. The ...

Watch this Scientific Journal Video about Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures at JoVE.com

Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures

Here we demonstrate a protocol to standardize sampling procedures of an established porcine model of acute myocardial infarction in order to increase its translational value in the understanding of the pathophysiology of myocardial ischemia/reperfusion injury and to test novel drug candidates.

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved ...

The overall goal of this porcine closed chest myocardial infarction model is to investigate myocardial ischemia reperfusion injury. This method can help to answer key questions in cardiovascular research such as investigating the pathophysiology of ischemia reperfusion injury in the context of acute myocardial infarction. The main advantage of this technique is that it allows an accurate determination of the infarct size and precise sampling technique for further analysis.Prepare the pig for the surgery and administer anesthetics as described in the text protocol. Start the dissection by freeing the carotid arteries on both sides. Cannulate them with 7-French sheaths.Next, cannulate the left jugular vein with a 7-French sheath for venous blood sampling. Then use standard blood collection tubes to withdraw baseline blood samples from the venous line. Collect five and 2.9 milliliters of blood into citrated and EDTA plasma collecting tubes respectively and immediately centrifuge at 2, 000 g for 15 minutes at four degrees Celsius.Next, collect 2.9 milliliters of blood into a serum tube and allow it to coagulate for 30 minutes at room temperature, then centrifuge it at 2, 000 g for 15 minutes at four degrees Celsius. Next, use fluoroscopic guidance to insert a pressure catheter via the previously placed sheath into the left carotid artery. Advance it into the left ventricle and then connect it to an acquisition system to record left ventricular pressure.Set up the acquisition system to continuously calculate and record the heart rate, the developed pressure, the contractility of the left ventricle, and the relaxation of the left ventricle during the entire experiment. Next, insert a guiding catheter via the previously placed sheath into the right carotid artery. Using x-ray guidance, advance the catheter into the left coronary artery and then to the LAD or Left Anterior Descending coronary artery.Once in position, inject contrast medium into the guiding catheter from a 20 milliliter syringe to perform a baseline coronary angiography. Next, assembly the PCI catheter and the appropriately sized coronary guide wire, then connect the PCI catheter to the inflation device prefilled with contrast medium. Insert the assembled system into the lumen of the guiding catheter and advance the guide wire into the LAD until it reaches beyond the first diagonal branch of the LAD.Next, use fluoroscopic guidance to advance the PCI catheter until it reaches about the middle of the LAD. Choose the LAD blocking site as described in the text protocol. Now remove the guide wire and increase the pressure in the inflation device to seven to 10 bar to inflate the balloon of the PCI catheter and induce myocardial ischemia.Keep the balloon inflated for one hour. Just after starting the ischemia, record five to 10 seconds of video while injecting contrast medium to have an angiogram of the balloon of the PCI catheter. Repeat this after 10 minutes to verify the occlusion of the LAD.From 15 to 40 minutes into the ischemia, gradually increase the fraction of inspired oxygen from 50 to 60%Always be quick to treat cardiac arrhythmias which typically occur between 20 and 40 minutes after coronary occlusion. An effective treatment to reestablish a regular heartbeat is to gently massage the neck on both sides just below the cheek. Start this treatment when extra systoles occur more than three times per minute, then inject the test substance intravenously through the central venous line and flush the line with 20 milliliters of saline.Next, perform another angiogram to confirm that the LAD is still occluded, then deflate the balloon of the PCI catheter and remove it from the guiding catheter. Immediately after removing the catheter, confirm the perfusion of the LAD distal to the occlusion using another angiogram. Take another angiogram after 10 minutes and whenever signs of myocardial ischemia are visible by ECG for more than five minutes.The ischemic myocardium is now allowed to reperfuse for two hours. Take plasma and serum samples at 10, 30, 60, and 115 minutes into the reperfusion. Also monitor blood gas analysis at 60 and 115 minutes into the reperfusion.After two hours of reperfusion, perform another angiogram, then reocclude the LAD. Reinsert the PCI catheter together with the guide wire to exactly the same position as used for the ischemia. Inflate the PCI catheter and confirm LAD occlusion by angiogram.Now remove the pressure catheter from the left ventricle and stop the recording. Finally, inject 100 milliliters of 2%Evans Blue in PBS into the central venous line and proceed with euthanizing the animal. After excising the heart, rinse it out with room temperature saline and weigh it.Within 30 to 40 minutes, cut the heart into slices starting about three to five millimeters from the apex and moving toward the chordae tendineae of the mitral valve. Cut perpendicular to the long axis using a sharp knife. Next, cut away the right ventricle and weigh the left ventricle slices to obtain its total weight.Then use a scalpel to dissect the slices to separate the Evans Blue negative tissue, which is ischemic, from the non-ischemic tissue which is Evans Blue positive. First, analyze the Evans Blue negative sections. They are the areas at risk.Weigh them all and put them all into a plastic container, then submerge them in 100 to 150 milliliters of freshly made TTC solution and incubate them for 20 minutes. During the incubation time, take samples from the most distal part of the injury. Embed them in OCT compound and store them at minus 80 degrees Celsius for further analysis.Transfer the remaining tissue into a 4%formaldehyde solution and store it at room temperature for future analysis. Now remove the pieces of the areas at risk from the TTC solution. The red-stained tissue is viable ischemic tissue and the non-stained tissue is necrotic ischemic tissue.Cut two small blocks of similar mass from both tissue types and embed them into OCT compound, then store at minus 80 degrees Celsius for further analysis. Store the remaining tissue in 4%formaldehyde at room temperature for 24 hours. The tissue is then stained and the Areas AT Risk or AAR were compared with the areas Not At Risk or ANR.The AAR expressed as a percentage of the LV showed no statistically significant differences between the FXIIa treated group and the control group. The infarct size also showed no differences between the groups. These data suggest that FXIIa inhibitor alone at the concentration used and duration of application could not protect the heart from myocardial IR injury.The cardiac muscle damage marker troponin-I was monitored in the blood. There was almost no change after one hour of ischemia, but after reperfusion, troponin-I levels steadily increased. After watching this video, you should have a good understanding of how to calculate accurately the infarct size and perform correct sampling.Once mastered, this technique can be done in six hours if it is performed properly. While attempting this procedure, it's important to remember to have a similar ischemic area at risk, inject Evans Blue intravenously, use freshly prepared TTC, and accurately calculate the NIT. Following this procedure, other methods like changing the ischemia and the reperfusion time can be performed in order to answer additional questions like the long-term effect of the treatment used to reduce reperfusion injury.

improvement-closed-chest-porcine-myocardial-infarction-model

Research

JoVE Journal

Medicine

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 ...

A Murine Closed-chest Model of Myocardial Ischemia and Reperfusion

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ischemia and reperfusion. Immune response includes cytokine expression and release or secretion of endogenous ligands of innate immune receptors. Activation of innate immunity can potentially modulate infarct size. We have modified an existing murine closed-chest model using hanging weights which could be useful for studying myocardial pre- and postconditioning and the role of innate immunity in myocardial ischemia and reperfusion. This model allows animals to recover from surgical trauma before onset of myocardial ischemia.
Volatile anesthetics have been intensely studied and their preconditioning effect for the ischemic heart is well known. However, this protective effect precludes its use in open chest models of coronary artery ligation. Thus, another advantage could be the use of the well controllable volatile anesthetics for instrumentation in a chronic closed-chest model, since their preconditioning effect lasts up to 72 hours. Chronic heart diseases with intermittent ischemia and multiple hit models are other possible applications of this model.
For the chronic closed-chest model, intubated and ventilated mice undergo a lateral blunt thoracotomy via the 4th intercostal space. Following identification of the left anterior descending a ligature is passed underneath the vessel and both suture ends are threaded through an occluder. Then, both suture ends are passed through the chest wall, knotted to form a loop and left in the subcutaneous tissue. After chest closure and recovery for 5 days, mice are anesthetized again, chest skin is reopened and hanging weights are hooked up to the loop under ECG control.
At the end of the ischemia/reperfusion protocol, hearts can be stained with TTC for infarct size assessment or undergo perfusion fixation to allow morphometric studies in addition to histology and immunohistochemistry.

Surgical trauma induces an inflammatory response. Cytokines and endogenous ligands are known to modulate myocardial infarct size following ischemia and reperfusion. We present a modified closed-chest model of murine ischemia and reperfusion using hanging weights to minimize effects of thoracotomy.

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ...

Myocardial Infarction and Functional Outcome Assessment in Pigs

Introduction of newly discovered cardiovascular therapeutics into first-in-man trials depends on a strictly regulated ethical and legal roadmap. One important prerequisite is a good understanding of all safety and efficacy aspects obtained in a large animal model that validly reflect the human scenario of myocardial infarction (MI). Pigs are widely used in this regard since their cardiac size, hemodynamics, and coronary anatomy are close to that of humans. Here, we present an effective protocol for using the porcine MI model using a closed-chest coronary balloon occlusion of the left anterior descending artery (LAD), followed by reperfusion. This approach is based on 90 min of myocardial ischemia, inducing large left ventricle infarction of the anterior, septal and inferoseptal walls. Furthermore, we present protocols for various measures of outcome that provide a wide range of information on the heart, such as cardiac systolic and diastolic function, hemodynamics, coronary flow velocity, microvascular resistance, and infarct size. This protocol can be easily tailored to meet study specific requirements for the validation of novel cardioregenerative biologics at different stages (i.e. directly after the acute ischemic insult, in the subacute setting or even in the chronic MI once scar formation has been completed). This model therefore provides a useful translational tool to study MI, subsequent adverse remodeling, and the potential of novel cardioregenerative agents.

This protocol describes the porcine myocardial infarction (MI) model using a 90 min closed-chest coronary balloon occlusion of the left anterior descending artery (LAD), followed by reperfusion. Furthermore, the protocol for several outcome parameters, such as cardiac function, hemodynamics, microvascular resistance, and infarct size, are also presented.

Introduction of newly discovered cardiovascular therapeutics into first-in-man trials depends on a strictly regulated ethical and legal roadmap. One ...

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 ...

Primary Outcome Assessment in a Pig Model of Acute Myocardial Infarction

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are therefore required to confine cardiac damage, promote survival and reduce the disease burden of heart failure. Large animal experiments are an essential part in the translational process from experimental to clinical therapies. To optimize clinical translation, robust and representative outcome measures are mandatory. The present manuscript aims to address this need by describing the assessment of three clinically relevant outcome modalities in a pig acute myocardial infarction (AMI) model: infarct size in relation to area at risk (IS/AAR) staining, 3-dimensional transesophageal echocardiography (TEE) and admittance-based pressure-volume (PV) loops. Infarct size is the main determinant driving the transition from AMI to heart failure and can be quantified by IS/AAR staining. Echocardiography is a reliable and robust tool in the assessment of global and regional cardiac function in clinical cardiology. Here, a method for three-dimensional transesophageal echocardiography (3D-TEE) in pigs is provided. Extensive insight into cardiac performance can be obtained by admittance-based pressure-volume (PV) loops, including intrinsic parameters of myocardial function that are pre- and afterload independent. Combined with a clinically feasible experimental study protocol, these outcome measures provide researchers with essential information to determine whether novel therapeutic strategies could yield promising targets for future testing in clinical studies.

Reliable and accurate outcome assessment is the key for translation of preclinical therapies into clinical treatment. The current paper describes how to assess three clinically relevant primary outcome parameters of cardiac performance and damage in a pig acute myocardial infarction model.

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are ...

Myocardial Infarction in Neonatal Mice, A Model of Cardiac Regeneration

Myocardial infarction induced by coronary artery ligation has been used in many animal models as a tool to study the mechanisms of cardiac repair and regeneration, and to define new targets for therapeutics. For decades, models of complete heart regeneration existed in amphibians and fish, but a mammalian counterpart was not available. The recent discovery of a postnatal window during which mice possess regenerative capabilities has led to the establishment of a mammalian model of cardiac regeneration. A surgical model of mammalian cardiac regeneration in the neonatal mouse is presented herein. Briefly, postnatal day 1 (P1) mice are anesthetized by isoflurane and placed on an ice pad to induce hypothermia. After the chest is opened, and the left anterior descending coronary artery (LAD) is visualized, a suture is placed around the LAD to inflict myocardial ischemia in the left ventricle. The surgical procedure takes 10-15 min. Visualizing the coronary artery is crucial for accurate suture placement and reproducibility. Myocardial infarction and cardiac dysfunction are confirmed by triphenyl-tetrazolium chloride (TTC) staining and echocardiography, respectively. Complete regeneration 21 days post myocardial infarction is verified by histology. This protocol can be used to as a tool to elucidate mechanisms of mammalian cardiac regeneration after myocardial infarction.

This protocol describes a highly reproducible model of cardiac regeneration by surgical induction of myocardial infarction in the left ventricle of postnatal day 1 mice. The method involves induction of hypothermic anesthesia and ligation of the left anterior descending coronary artery.

Myocardial infarction induced by coronary artery ligation has been used in many animal models as a tool to study the mechanisms of cardiac repair and ...

A Closed-chest Model to Induce Transverse Aortic Constriction in Mice

Research on cardiac hypertrophy and heart failure is frequently based on pressure overload mouse models induced by TAC. The standard procedure is to perform a partial thoracotomy to visualize the transverse aortic arch. However, the surgical trauma caused by the thoracotomy in open-chest models changes the respiratory physiology as the ribs are dissected and left unattached after chest closure. To prevent this, we established a minimally invasive, closed chest approach via lateral thoracotomy. Herein we approach the aortic arch via the 2nd intercostal space without entering the chest cavities, leaving the mouse with a less traumatic injury to recover from. We perform this operation using standard laboratory settings for open chest TAC procedures with equal survival rates. Apart from maintaining physiological breathing patterns due to the closed chest approach, the mice seem to benefit by showing rapid recovery, as the less invasive technique appears to facilitate a fast healing process and to reduce immune response after trauma.

Here, we present a protocol of Transverse Aortic constriction (TAC) via a lateral thoracotomy. This technique is a minimally invasive, closed chest surgical procedure aiming to simulate pressure overload and heart failure in mice utilizing standard TAC laboratory settings.

Research on cardiac hypertrophy and heart failure is frequently based on pressure overload mouse models induced by TAC. The standard procedure is to ...

A Cryoinjury Model to Study Myocardial Infarction in the Mouse

The use of animal models is essential for developing new therapeutic strategies for acute coronary syndrome and its complications. In this article, we demonstrate a murine cryoinjury infarct model that generates precise infarct sizes with high reproducibility and replicability. In brief, after intubation and sternotomy of the animal, the heart is lifted from the thorax. The probe of a handheld liquid nitrogen delivery system is applied onto the myocardial wall to induce cryoinjury. Impaired ventricular function and electrical conduction can be monitored with echocardiography or optical mapping. Transmural myocardial remodeling of the infarcted area is characterized by collagen deposition and loss of cardiomyocytes. Compared to other models (e.g., LAD-ligation), this model utilizes a handheld liquid nitrogen delivery system to generate more uniform infarct sizes.

This article demonstrates a model to study cardiac remodeling after myocardial cryoinjury in mice.

The use of animal models is essential for developing new therapeutic strategies for acute coronary syndrome and its complications. In this article, we ...

Biventricular Assessment of Cardiac Function and Pressure-Volume Loops by Closed-Chest Catheterization in Mice

Assessment of cardiac function is essential to conduct cardiovascular and pulmonary-vascular preclinical research. Pressure-volume loops (PV loops) generated by recording both pressure and volume during cardiac catheterization are vital when assessing both systolic and diastolic cardiac function. Left and right heart function are closely related, reflected in ventricular interdependence. Thus, recording biventricular function in the same animal is important to get a complete assessment of cardiac function. In this protocol, a closed chest approach to cardiac catheterization consistent with the way catheterization is performed in patients is adopted in mice. While challenging, the closed chest strategy is a more physiological approach, because opening the chest results in major changes in preload and afterload that create artifacts, most notably a fall in systemic blood pressure. While high-resolution echocardiography is used to assess rodents, cardiac catheterization is invaluable, particularly when assessing diastolic pressures in both ventricles.
Described here is a procedure to perform invasive, closed chest, sequential left and right ventricular pressure-volume (PV) loops in the same animal. PV loops are acquired using&#160;admittance technology with a mouse pressure-volume catheter and pressure-volume system acquisition. The procedure is described, beginning with the neck dissection, which is required to access the right jugular vein and the right carotid artery, to the insertion and positioning of the catheter, and finally the data acquisition. Then, the criteria required to ensure the acquisition of high-quality PV loops are discussed. Finally, the analysis of the left and right ventricular PV loops and the different hemodynamic parameters available to quantify systolic and diastolic ventricular function are briefly described.

Presented here is a protocol to assess biventricular heart function in mice by generating pressure-volume (PV) loops from the right and left ventricle in the same animal using closed chest catheterization. The focus is on the technical aspect of surgery and data acquisition.

Assessment of cardiac function is essential to conduct cardiovascular and pulmonary-vascular preclinical research. Pressure-volume loops (PV loops) ...

Post-Myocardial Infarction Heart Failure in Closed-chest Coronary Occlusion/Reperfusion Model in G&#246;ttingen Minipigs and Landrace Pigs

The development of heart failure is the most powerful predictor of long-term mortality in patients surviving acute myocardial infarction (MI). There is an unmet clinical need for prevention and therapy of post-myocardial infarction heart failure (post-MI HF). Clinically relevant pig models of post-MI HF are prerequisites for final proof-of-concept studies before entering into clinical trials in drug and medical device development.
Here we aimed to characterize a closed-chest porcine model of post-MI HF in adult G&#246;ttingen minipigs with long-term follow-up including serial cardiac magnetic resonance imaging (CMRI) and to compare it with the commonly used Landrace pig model.
MI was induced by intraluminal balloon occlusion of the left anterior descending coronary artery for 120 min in G&#246;ttingen minipigs and for 90 min in Landrace pigs, followed by reperfusion. CMRI was performed to assess cardiac morphology and function at baseline in both breeds and at 3 and 6 months in G&#246;ttingen minipigs and at 2 months in Landrace pigs, respectively.
Scar sizes were comparable in the two breeds, but MI resulted in a significant decrease of left ventricular ejection fraction (LVEF) only in G&#246;ttingen minipigs, while Landrace pigs did not show a reduction of LVEF. Right ventricular (RV) ejection fraction increased in both breeds despite the negligible RV scar sizes. In contrast to the significant increase of left ventricular end-diastolic (LVED) mass in Landrace pigs at 2 months, G&#246;ttingen minipigs showed a slight increase in LVED mass only at 6 months.
In summary, this is the first characterization of post-MI HF in G&#246;ttingen minipigs in comparison to Landrace pigs, showing that the G&#246;ttingen minipig model reflects post-MI HF parameters comparable to the human pathology. We conclude that the G&#246;ttingen minipig model is superior to the Landrace pig model to study the development of post-MI HF.

Post-Myocardial Infarction Heart Failure in Closed-chest Coronary Occlusion/Reperfusion Model in G&amp;#246;ttingen Minipigs and Landrace Pigs

The overall goal of the current study is to present the techniques of induction of myocardial infarction (MI) and post-myocardial infarction heart failure (post-MI HF) in closed-chest, adult G&#246;ttingen minipigs and the characterization of post-MI HF model in G&#246;ttingen minipigs as compared to Landrace pigs.

The development of heart failure is the most powerful predictor of long-term mortality in patients surviving acute myocardial infarction (MI). There is an ...