Name: surgical swine model of chronic cardiac ischemia treated by off-pump coronary artery bypass graft surgery
Uploaded: 2018-03-27T13:00:00.000+00:00
Duration: 9 min 12 s
Description: Watch this Scientific Journal Video about Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery at JoVE.com

This work was supported by the VA Merit Review #I01 BX000760 (RFK) from the United States (U.S.) Department of Veterans Affairs BLR&amp;D. The contents of this work do not represent the views of the U.S. Department of Veterans Affairs of the United States Government.

All animal studies were approved by the Institutional Animal Care and Use Committees of the Minneapolis VA Medical Center and the University of Minnesota. Follow current National Institutes of Health guidelines for the use and care of laboratory animals.
1. Hibernation Surgery
<ol>
	<li>Animal Preparation
	<ol>
		<li>To create a model of hibernating myocardium, use 5-week old, female, Yorkshire pigs, which weigh in the range of 8-10 kg with 9.2 kg as the average weight.</li>
		<li>For pre-surgical health monitoring, weigh the animal within 3 days prior to surgery.</li>
		<li>Fast the animal for 12 h before starting anesthesia. Ensure that water is available at all times for fasting animals.</li>
		<li>Give SR Buprenorphine 0.18 mg/kg IM 24 h prior to the surgery.</li>
	</ol>
	</li>
	<li>Induction
	<ol>
		<li>Sedate the animal with 6.6 mg/kg tiletamine-zolazepam and xylazine cocktail given intramuscularly. Allow 5-15 min for the drug cocktail to take effect.</li>
		<li>Prepare the ear vein aseptically by wiping three times with 70% isopropyl alcohol for IV catheter placement. 
		NOTE: If an ear vein is not adequate, another peripheral vein may be used (i.e. cephalic).</li>
		<li>Apply ophthalmic ointment to both eyes to prevent corneal drying.</li>
		<li>If necessary, induce anesthesia by administering 1-2 mg/kg of propofol IV or masked with 3 L/min of oxygen and 3% isoflurane, to allow for tracheal intubation. 
		&#8203;NOTE: The animal is considered appropriately anesthetized when the blink reflex or jaw tone is absent.</li>
		<li>Intubate the animal with an appropriately sized endotracheal tube.</li>
	</ol>
	</li>
	<li>Surgery
	<ol>
		<li>Once the animal is anesthetized, shave the left thoracic area for the surgery.</li>
		<li>Initiate the mechanical ventilation at 10-15 breaths per min. Set oxygen at 1-4 L/min, and isoflurane between 1.0 and 3.0% as needed to maintain a surgical plane of anesthesia.</li>
		<li>Place the monitoring devices on the animal. Monitoring devices should include ECG, blood pressure, temperature, and pulse oximeter.</li>
		<li>Connect the IV catheter to an IV drip with 0.9% normal saline at a rate of 5-10 mL/kg/h.</li>
		<li>Aseptically prepare the left lateral chest with an FDA approved surgical scrub.</li>
		<li>Evaluate the depth of anesthesia every 5-15 min. Record the baseline vital signs (heart rate, ECG, SpO2, NIBP, ETCO2 and temperature) every 15 min. 
		NOTE: The animal is considered appropriately anesthetized when the blink reflex or jaw tone is absent.</li>
		<li>With the animal laying on its right side, place sterile drapes the left side of the chest from the spine to the scapula centering the third rib space in the sterile field. 
		NOTE: The sterile field involves left front shoulder including the axillary area continuing to the sternum to the sixth rib space cranially.</li>
		<li>Gently scrub the field with an FDA approved surgical method such as chlorhexidine gluconate or an iodine surgical scrub for 2 min using a target pattern.</li>
		<li>Rinse the field with water and wash it two more times with an FDA approved method as above for 2 min. Rinse the surgical field with water in between washes, then pat dry with sterile toweling or 4 x 4 cm gauze sponges.</li>
		<li>Spray the area with an iodine solution and drape the entire animal (except the surgical field) with sterile drapes. Use steam or gas sterilization to sterilize the instruments, gowns, and drapes for the procedure.</li>
		<li>Administer an intercostal nerve block using 0.3 mL of 0.5% bupivicaine at the 2nd, 3rd and 4th ribs.</li>
		<li>Give 125 mg of cefazolin IV before opening the chest. 
		NOTE: 1.5 mg/kg succinylcholine IV may be given as a paralytic agent to reduce muscle movement per surgeon&#39;s request during the opening of the chest cavity.</li>
		<li>Expose the heart via a left thoracotomy. Prior to heart manipulation, give a 2 mg/kg IV bolus of lidocaine to prevent arrhythmia. Make the lateral 3rd space thoracotomy incision with monopolar electrocautery. The incision should extend from the cranial aspect of the scapula to the axillary area for approximately 10 cm. Use a cautery to incise the skin and underlying musculature to allow the entry into the chest cavity.</li>
		<li>Place a finochietto rib retractor and enter the pleural space at the third intercostal space to retract the lung.</li>
		<li>Sharply incise the pericardium and retract to the side using 2-0 polyglactin stay sutures, exposing the LAD artery and vein. Retract the left atrial appendage with a gauze-covered spatula retractor.</li>
		<li>Using iris scissors, open the adventitia over the LAD.</li>
		<li>Bluntly dissect an approximately 0.25 cm portion of the LAD artery approximately 1 cm distal to the LAD and circumflex artery junction. Use a right-angle clamp to encircle the LAD.</li>
		<li>Place two 4-0 polyester sutures around the artery without placing any tension.</li>
		<li>Place a plastic c-shaped constrictor with an internal diameter of 1.5 mm on the LAD proximal to the first diagonal without occluding the vessel.</li>
		<li>Secure it with two 4-0 polyester ties encircling the LAD.</li>
		<li>Loosely close the pericardium using 2-0 polyglactin suture in a simple interrupted pattern.</li>
		<li>Perform a breath hold to remove air from the chest while the intercostal muscle layer is closed. Carefully monitor the airway pressure manometer on the anesthesia machine to maintain the pressure in a proper range of 20-30 cm of water and release when complete. 
		NOTE: This eliminates the need for a chest tube in the post-operative period.</li>
		<li>Close the muscle and skin layers in the standard fashion using 2-0 and 3-0 absorbable suture.</li>
		<li>Use skin adhesive over the incision for skin closure.</li>
		<li>Administer a total dose of 1 mg/kg bupivacaine intramuscularly at multiple sites along the length of the incision at the end of the procedure. Administer meloxicam 0.2 mg/kg SQ before transport to the recovery area.</li>
		<li>Wean the animal off the ventilator as the skin layer is closed.</li>
		<li>Leave the animal connected to the anesthesia machine until it can spontaneously breathe and protective reflexes begin to return.</li>
		<li>Do not remove the endotracheal tube until the animal can swallow to protect its airway.</li>
		<li>Apply a sterile, non-adherent dressing with triple-antibiotic ointment over the incision.</li>
	</ol>
	</li>
	<li>Post-Surgery
	<ol>
		<li>Record the heart rate, respiration rate, body temperature and mucous membrane color every 15 min until the animal can hold a sternal position unassisted.</li>
		<li>Do not leave the animal unattended until it can lift and hold its head up and can stand unassisted.</li>
		<li>Give meloxicam (0.2 mg/kg) subcutaneously.</li>
		<li>Administer sustained release buprenorphine 6 h following the initial pre-surgical dose.</li>
		<li>Leave the dressing on the incision for up to 3 days, if it remains clean and dry. Replace the dressing if it becomes soiled.</li>
		<li>Monitor the pain level, general well-being and the condition of the incision for 5 days following the procedure. 
		NOTE: A piglet grimace scale is now available to assess the level of pain in these animals post-operatively14. Use half dose meloxicam as needed once per day for breakthrough pain.</li>
		<li>Single-house the animal during the recovery period of 5 day to limit activity and allow the wound to heal.</li>
		<li>Allow 8 weeks to fully develop the hibernating myocardium phenotype.</li>
	</ol>
	</li>
</ol>
2. Revascularization or Off Pump Bypass
<ol>
	<li>Animal Preparation
	<ol>
		<li>Weigh the animal within 3 days prior to surgery.</li>
		<li>Fast the animal for 12 h prior to surgery. Ensure that water is available at all times for fasting animals.</li>
		<li>Give sustained release buprenorphine 0.18 mg/kg intramuscularly 24 h prior to the surgery.</li>
	</ol>
	</li>
	<li>Induction
	<ol>
		<li>Sedate the animal with 6.6 mg/kg tiletamine-zolazepam/xylazine cocktail intramuscularly. 5-15 min after the sedation, prepare the ear vein aseptically for catheter placement. 
		&#8203;NOTE: If an ear vein is not adequate, another peripheral vein may be used (i.e. cephalic).</li>
		<li>Apply ophthalmic ointment to both eyes.</li>
		<li>Induce anesthesia with 1-2 mg/kg of propofol IV.</li>
		<li>Intubate the animal with an appropriately sized endotracheal tube.</li>
	</ol>
	</li>
	<li>Surgery
	<ol>
		<li>Shave the animal&#39;s sternum, left lateral chest and femoral triangles for the surgery.</li>
		<li>Set mechanical ventilation to 10-15 breaths per minute, oxygen at 1-4 L/min, and isoflurane at 1.0-3.0% as needed to maintain a surgical plane of anesthesia.</li>
		<li>Position the monitoring equipments (heart rate, ECG, SpO2, direct blood pressure, ETCO2 and temperature) on the animal.</li>
		<li>Connect the IV catheter to an IV drip with normal saline or LRS.</li>
		<li>Aseptically prepare the skin with povidone iodine scrub or other FDA approved method.</li>
		<li>Evaluate the animal for the depth of anesthesia. 
		NOTE: The animal is considered deeply anesthetized when the eye or jaw reflex is absent.</li>
		<li>Position the animal dorsally, prepare the skin as previously described and drape the animal with sterile towels.</li>
		<li>Perform a cut down to the femoral artery and cannulation. Use monopolar electrocautery to create an approximately 3 cm skin incision over the femoral artery to expose it for cannulation.</li>
		<li>Perform a femoral nerve block after the incision is made, to allow precise placement of drug. Connect the femoral cannula to a transducer to monitor blood pressures during the surgery.</li>
		<li>Use electro-cautery to incise from the manubrium to the xiphoid process, as well as to incise the muscle, adipose, and connective tissue to the level of the sternum.</li>
		<li>Divide the sternum with an oscillating saw. 
		NOTE: Using an oscillating saw, rather than a standard sternal saw avoids potential myocardial injury from pericardial adhesions as a result of the thoracotomy for constrictor placement on the LAD.</li>
		<li>Administer lidocaine (2 mg/kg IV loading dose, 50 &#181;g/kg/min continuous IV infusion) to prevent arrhythmias. Dilute lidocaine in a 500 mL bag of normal saline at a concentration of 1 mg/mL.</li>
		<li>Divide the posterior sternal plate with straight Mayo scissors.</li>
		<li>Use a chest retractor to expose the thoracic cavity.</li>
		<li>Take down the adhesions with monopolar electro-cautery.</li>
		<li>Using the same retractor, with gentle elevation of the left sternal border by an assistant, dissect the left internal mammary artery free from the chest wall.</li>
		<li>Control the arterial branches with hemoclips.</li>
		<li>Heparinize the animal with 100-300 units/kg of heparin IV.</li>
		<li>After 3 min, divide the artery with the distal end over sewn. Prepare the proximal end for grafting.</li>
		<li>Open and retract the pericardium. Confirm that the length of the LIMA is adequate to reach the appropriate anastomotic site on the LAD.</li>
		<li>Perform the LIMA to LAD anastomosis with 7-0 polypropylene suture using an off pump technique with a cardiac stabilizer, spring form clip, and appropriately sized intraluminal devices.</li>
		<li>Place a chest tube between the ribs on the left lateral chest, externalized and attached to vacuum to remove air from the chest cavity for 15-30 min.</li>
		<li>Approximate the sternum with #5 polyester sutures using a figure eight pattern.</li>
		<li>Close the muscle, subcutaneous and skin layers in the usual fashion as described in the Hibernation surgery. Remove the chest tube while performing a Valsalva maneuver to remove any residual air from the chest cavity and close the incision with one skin suture.</li>
		<li>Apply skin adhesive over the skin to protect the sternal incision. Gently remove the femoral catheter and repair the artery using 7-0 polypropylene suture in a purse string pattern. Close the skin using 2-0 polyglactin suture in a subcuticular pattern.</li>
		<li>Administer a total dose of 1 mg/kg bupivacaine intramuscularly at multiple sites along the length of the incision at the end of the procedure.</li>
		<li>Administer meloxicam 0.2 mg/kg subcutaneously before transport to the recovery area.</li>
		<li>Follow the post-operative protocol in the hibernation procedure.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Mozaffarian, D., 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=Heart+Disease+and+Stroke+Statistics-2016+Update+A+Report+From+the+American+Heart+Association.">Heart Disease and Stroke Statistics-2016 Update A Report From the American Heart Association.</a> Circulation. 133 (4), 350 (2015).</li><li>Di Carli, M. F., 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=Value+of+metabolic+imaging+with+positron+emission+tomography+for+evaluating+prognosis+in+patients+with+coronary+artery+disease+and+left+ventricular+dysfunction.">Value of metabolic imaging with positron emission tomography for evaluating prognosis in patients with coronary artery disease and left ventricular dysfunction.</a> Am J Cardiol. 73 (8), 527-533 (1994).</li><li>Gerber, B. L., 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=Prognostic+value+of+myocardial+viability+by+delayed-enhanced+magnetic+resonance+in+patients+with+coronary+artery+disease+and+low+ejection+fraction:+impact+of+revascularization+therapy.">Prognostic value of myocardial viability by delayed-enhanced magnetic resonance in patients with coronary artery disease and low ejection fraction: impact of revascularization therapy.</a> J Am Coll Cardiol. 59 (9), 825-835 (2012).</li><li>McFalls, E., 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=Regional+glucose+uptake+within+hypoperfused+swine+myocardium+as+measured+by+positron+emission+tomography.">Regional glucose uptake within hypoperfused swine myocardium as measured by positron emission tomography.</a> Am J Physiol-Heart C. 272 (1), 343-349 (1997).</li><li>Velazquez, E. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary-artery+bypass+surgery+in+patients+with+left+ventricular+dysfunction.">Coronary-artery bypass surgery in patients with left ventricular dysfunction.</a> New Engl J Med. 364 (17), 1607-1616 (2011).</li><li>Canty, J. M., Fallavollita, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hibernating+myocardium.">Hibernating myocardium.</a> J Nucl Cardiol. 12 (1), 104-119 (2005).</li><li>Joyce, D., 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=Revascularization+and+ventricular+restoration+in+patients+with+ischemic+heart+failure:+the+STICH+trial.">Revascularization and ventricular restoration in patients with ischemic heart failure: the STICH trial.</a> Curr Opin Cardiol. 18 (6), 454-457 (2003).</li><li>Shah, B. N., Khattar, R. S., Senior, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hibernating+myocardium:+current+concepts,+diagnostic+dilemmas,+and+clinical+challenges+in+the+post-STICH+era.">The hibernating myocardium: current concepts, diagnostic dilemmas, and clinical challenges in the post-STICH era.</a> Eur Heart J. 34 (18), 1323-1336 (2013).</li><li>Stone, L. L. H., 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=Magnetic+resonance+imaging+assessment+of+cardiac+function+in+a+swine+model+of+hibernating+myocardium+3+months+following+bypass+surgery.">Magnetic resonance imaging assessment of cardiac function in a swine model of hibernating myocardium 3 months following bypass surgery.</a> J Thorac Cardiov Sur. , (2016).</li><li>Kukulski, T., 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=Implication+of+right+ventricular+dysfunction+on+long-term+outcome+in+patients+with+ischemic+cardiomyopathy+undergoing+coronary+artery+bypass+grafting+with+or+without+surgical+ventricular+reconstruction.">Implication of right ventricular dysfunction on long-term outcome in patients with ischemic cardiomyopathy undergoing coronary artery bypass grafting with or without surgical ventricular reconstruction.</a> J Thorac Cardiov Sur. 149 (5), 1312-1321 (2014).</li><li>Rahimtoola, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hibernating+myocardium.">The hibernating myocardium.</a> Am Heart J. 117 (1), 211-221 (1989).</li><li>Fallavollita, J. A., Logue, M., Canty, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+of+hibernating+myocardium+in+pigs+with+a+chronic+left+anterior+descending+coronary+artery+stenosis:+absence+of+progressive+fibrosis+in+the+setting+of+stable+reductions+in+flow,+function+and+coronary+flow+reserve.">Stability of hibernating myocardium in pigs with a chronic left anterior descending coronary artery stenosis: absence of progressive fibrosis in the setting of stable reductions in flow, function and coronary flow reserve.</a> J Am Coll Cardiol. 37 (7), 1989-1995 (2001).</li><li>White, F. C., Carroll, S. M., Magnet, A., Bloor, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary+collateral+development+in+swine+after+coronary+artery+occlusion.">Coronary collateral development in swine after coronary artery occlusion.</a> Circ Res. 71 (6), 1490-1500 (1992).</li><li>Viscardi, A. V., Hunniford, M., Lawlis, P., Leach, M., Turner, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+Piglet+Grimace+Scale+to+Evaluate+Piglet+Pain+Using+Facial+Expressions+Following+Castration+and+Tail+Docking:+A+Pilot+Study.">Development of a Piglet Grimace Scale to Evaluate Piglet Pain Using Facial Expressions Following Castration and Tail Docking: A Pilot Study.</a> Front Vet Sci. 4, 51 (2017).</li><li>Holley, C. T., Long, E. K., Lindsey, M. E., McFalls, E. O., Kelly, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recovery+of+hibernating+myocardium:+what+is+the+role+of+surgical+revascularization.">Recovery of hibernating myocardium: what is the role of surgical revascularization.</a> J Cardiac Surg. 30 (2), 224-231 (2015).</li><li>Cooper, H. A., Braunwald, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+importance+of+stunned+and+hibernating+myocardium.">Clinical importance of stunned and hibernating myocardium.</a> Coronary Artery Dis. 12 (5), 387-392 (2001).</li><li>McFalls, E. O., 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=Utility+of+positron+emission+tomography+in+predicting+improved+left+ventricular+ejection+fraction+after+coronary+artery+bypass+grafting+among+patients+with+ischemic+cardiomyopathy.">Utility of positron emission tomography in predicting improved left ventricular ejection fraction after coronary artery bypass grafting among patients with ischemic cardiomyopathy.</a> Cardiology. 93 (1-2), 105-112 (2000).</li><li>Pasquet, 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=Prediction+of+global+left+ventricular+function+after+bypass+surgery+in+patients+with+severe+left+ventricular+dysfunction.+Impact+of+pre-operative+myocardial+function,+perfusion,+and+metabolism.">Prediction of global left ventricular function after bypass surgery in patients with severe left ventricular dysfunction. Impact of pre-operative myocardial function, perfusion, and metabolism.</a> Eur Heart J. 21 (2), 125-136 (2000).</li></ol>

The authors have nothing to disclose.

Here, we show that our swine model of HM accurately mimics the clinical experience of patients with single vessel disease and preserved left ventricular function. Prior to the revascularization, animals with single vessel HM exhibit minimal impairment in global function as measured by ejection fraction, but show significant reduction in regional wall thickening. Following the revascularization, CMR imaging at one or three months of recovery demonstrates preserved viability and graft patency but persistent regional dysfunction, as noted by the estimates of contractile reserve with low dose dobutamine stress testing.
There are several critical steps for the initial hibernation operation. Entering the chest at the third intercostal space allows for the easiest access to the proximal LAD. The retraction of the left atrial appendage with a moist gauze facilitates&#160;visualization of the vessel without inducing arrhythmias. The assistance to expose the LAD minimizes the bleeding and secures the constrictor. Chest closure with the Valsalva maneuver to evacuate the air prevents pneumothorax.
There are several critical steps for a successful revascularization procedure. Appropriate depth of anesthesia and use of paralytic agent ensured no movement during the anastomosis portion of the procedure. Use of lidocaine and 200p units/kg Heparin eliminates arrhythmia and thrombosis events. Using a femoral arterial line to maintain appropriate blood pressure monitoring is critical to the hemodynamic stability of the animal. Use a flo-thru device to improve animal stability during the anastomosis and alleviate the need for retraction stabilizing tapes. While sewing the graft, an O2 blower is helpful to visualize the anastomosis.
During the revascularization procedure, if arrhythmia is observed, the animal may require a second dose of lidocaine. If the LAD is difficult to visualize, place the stabilizer after dissection of epicardial fat or fibrinous tissue. Anesthetically, once the stabilizer is placed and the heart is lifted, mild decreases in arterial blood pressure will be noted in addition to ST depression on the ECG. These abnormalities are usually tolerable and do not require intervention. If changes in cardiovascular stability are more dramatic, a dose of phenylephrine (5-20 &#181;g/kg IV) may be given IV to increase arterial blood pressure. Epinephrine (0.1 &#181;g/kg IV; diluted 1:10,000) would be used as an emergency rescue drug if changes are life threatening. Blood loss is replaced with a crystalloid solution IV. A bolus of 100-300 mL of normal saline is used for additional blood pressure support. The LIMA is most easily taken down as a near-skeletonized vessel, but it may be necessary to have papaverine available if a spasm occurs.
Our model uses off-pump surgery rather than on-pump for the revascularization, as this allows us to minimize the operative time and avoid the cannulation of the aorta and right atrium with full heparinization. It also reduces the risk of post-operative bleeding and/or cardiac tamponade, simplifying the animal&#39;s recovery. Of note, there is no similar model of coronary bypass surgery in a model of HM in an animal that is then allowed to recover for 30-120 days. These are presumed advantages based on clinical experience in patients undergoing CABG both on and off pump.
This technique can be expanded to involve multiple coronary artery disease by the placement of a constrictor on the circumflex artery at the same time as the LAD or as an alternative vessel. This two-vessel disease model would result in more rapid development of ischemic cardiomyopathy and greater understanding of resultant myocardial adaptions. It is a model that would still allow for ongoing adjunctive interventions including pharmacologic, cell based or mechanical options.
This complex model of the revascularization of HM reflects the clinical difficulty of managing patients with viable but chronically ischemic, dysfunctional myocardium. There is a high prevalence of patients with HM, often presenting with various comorbidities and cardiovascular structural diseases16, and are at risk for sudden cardiac death (SCD)6. The revascularization of viable, impaired myocardium is associated with a 79% reduction in annual death rate3. In fact, we have shown that revascularization of patients with viable hibernating myocardium, as defined by PET imaging, is associated with a greater degree of improvement in LV ejection fraction at 6 weeks following CABG17. In animals with HM, circumferential strain is impaired at baseline, but there is evidence of contractile reserve under inotropic stimulation with a low dose of dobutamine. The presence of contractile reserve is one of the most specific indicators of myocardial viability 18, and the presence of such viability is a predictor of the potential benefit of bypass surgery when present.
Our model is limited by the necessity of using young, healthy animals to create the model of HM. It is necessary to use a young animal to implant the constrictor on the LAD artery as juvenile animals have arteries that are small enough to place the constrictor around without creating immediate stenosis. This model cannot be achieved by beginning with adult pigs, though that would more closely simulate the clinical experience, due to size limitations of both the constrictor, as well as the size of standard surgical and MRI equipment.
An additional limitation is that this animal model of HM only allows the analysis of the effects of a single territory of chronic ischemia, whereas clinical cases are typically far more complex, and may respond differently to the revascularization.

Coronary heart disease (CHD) affects an estimated 15.5 million people in the United States 1 and is one of the leading causes of death globally. While the mortality rate associated with CHD has gone down in recent years, the incidence and burden on patients and the health care system remain high 1. Primary treatment of severe CAD is revascularization, which improves survival and reduces angina2,3,4. However, cardiac function often remains depressed, especially under increased workload and can progress to heart failure5,6. Clinical trials of coronary artery bypass surgery (CABG) for chronic ischemia demonstrate improvement in survival and symptoms, but ejection fraction shows only modest improvements of 8-10% 7,8. Our innovative and well-characterized swine model of chronic myocardial ischemia is a model of clinical CAD with progressive vascular stenosis. We have demonstrated reduced myocardial contractility resulting from gradual reduction in blood flow 9. The myocardium does not infarct and can remain viable in this scenario. Recovery is possible, though outcomes are variable even with timely revascularization. Chronically ischemic myocardium that remains viable has been characterized by reduced blood flow and function at rest with retained contractile reserve has been termed HM and treatment requires CABG.Although the revascularization of HM should restore contractile function, experimental and clinical observations demonstrate that the recovery is incomplete8,10.
HM is characterized by the presence of viable yet dysfunctional myocardium in the presence of reduced regional blood flow11. Despite impaired contractility and metabolic activity at rest, HM is able to demonstrate functional and metabolic reserve under inotropic stimulation12. HM is suspected in a majority of patients with CAD, and encompasses a broad spectrum of disease. In this protocol, we demonstrate our established swine model of HM bypassed with left internal mammary artery (LIMA) to LAD artery that mimics the clinical scenario. The swine provide an excellent model of heart disease over other large animals as they do not have epicardial bridging collaterals. This allows the stenosis of the LAD alone to result in regional ischemia13.
Here, we describe the surgical method of inducing hibernating myocardium in swine by creating single-vessel stenosis at the LAD artery. Once chronic ischemia has been established (8 weeks post implant of LAD constrictor), we describe the method of recreating the clinical treatment for HM in our swine model: an off-pump coronary artery bypass graft. These surgical methods can be used to not only study a clinically relevant model of chronic cardiac ischemia, but also to investigate the effects of bypass surgery on cardiac ischemia as well as test potential alternate or adjunctive therapies for cardiac ischemia.

<table><tbody><tr><td>Bair Hugger</td><td>3M</td><td>Model 505</td><td>Patient Warming system</td></tr><tr><td>SR Buprenorphine 10 mg/mL</td><td>Abbott Labs</td><td>NADA 141-434</td><td>Post operative Analgesic</td></tr><tr><td>Surgical Spring Clip</td><td>Applied Medical</td><td>A1801</td><td>Clamp end of LIMA after takedown</td></tr><tr><td>Arterial Line Kit</td><td>Arrow</td><td>ASK-04510-HF</td><td>Femoral catheter for blood pressure monitoring</td></tr><tr><td>1000mL 0.9% Sodium chloride</td><td>Baxter</td><td>2B1324X</td><td>IV replacement fluid</td></tr><tr><td>250 mL 0.9% saline</td><td>Baxter</td><td>&amp;nbsp;UE1322D</td><td>Replacement IV Fluid&amp;nbsp;</td></tr><tr><td>500mL 0.9% Sodium chloride</td><td>Baxter</td><td>2B1323Q</td><td>Drug delivery, Provide mist for Blower Mister</td></tr><tr><td>Flo-thru 1.0</td><td>Baxter</td><td>FT-12100</td><td>used to anastomos LIMA to L</td></tr><tr><td>Flo-thru 1.25</td><td>Baxter</td><td>FT-12125</td><td></td></tr><tr><td>Flo-thru 1.5</td><td>Baxter</td><td>FT-12150</td><td></td></tr><tr><td>Flo-thru 2.0</td><td>Baxter</td><td>FT-12200</td><td></td></tr><tr><td>Cloroprep</td><td>Becton Dickenson</td><td>260815</td><td>Surgical skin prep</td></tr><tr><td>Meloxicam</td><td>Boehringer Ingelheim Vetmedica, Inc.</td><td>0010-6013-01</td><td>NSAID for analgesia</td></tr><tr><td>Hypafix</td><td>BSN Medical</td><td>4210</td><td>Secure wound dressing and IV catheters</td></tr><tr><td>IV Tubing for Blower Mister</td><td>Carefusion</td><td>42493E</td><td>Adapts to IV Fluids for Blower/Mister</td></tr><tr><td>Bovie Cautery hand piece&amp;nbsp;</td><td>Covidien</td><td>E2516</td><td>Hemostasis&amp;nbsp;</td></tr><tr><td>Chest Tube</td><td>Covidien</td><td>8888561043</td><td>Evacuates air from chest cavity&amp;nbsp;</td></tr><tr><td>Monopolar Cautery&amp;nbsp;</td><td>Covidien</td><td>Valleylab FT10</td><td>Hemostasis&amp;nbsp;</td></tr><tr><td>Telpha pad</td><td>Covidien</td><td>2132</td><td>Sterile wound dressing</td></tr><tr><td>4-0 Tevdek II Strands</td><td>Deknatel</td><td>7-922</td><td>Suture to secure constrictor around LAD</td></tr><tr><td>Propofol</td><td>Diprivan</td><td>269-29</td><td>Induction agent</td></tr><tr><td>&amp;nbsp;long blade for laryngoscope&amp;nbsp;</td><td>DRE</td><td>12521</td><td>Allows for visualization of trachea for intubation</td></tr><tr><td>ECG Pads</td><td>DRE</td><td>1496</td><td>Monitor heart rhythm</td></tr><tr><td>laryngoscope&amp;nbsp;</td><td>DRE</td><td>12515</td><td></td></tr><tr><td>Anesthesia Machine + ventilator</td><td>DRE Drager- Fabius Tiro</td><td>DRE0603FT</td><td>Deliver Oxygen and inhalant to patient</td></tr><tr><td>&amp;nbsp;5 Ethibond&amp;nbsp;</td><td>Ethicon</td><td>MG46G</td><td>Suture</td></tr><tr><td>0 Vicryl</td><td>Ethicon</td><td>J208H</td><td>Suture</td></tr><tr><td>2-0 Vicryl</td><td>Ethicon</td><td>J317H</td><td>Suture</td></tr><tr><td>3-0 Vicryl</td><td>Ethicon</td><td>VCP824G</td><td>Suture</td></tr><tr><td>7-0 Prolene</td><td>Ethicon</td><td>M8702</td><td>Suture</td></tr><tr><td>Dermabond</td><td>Ethicon</td><td>DNX12</td><td>Skin adhesive</td></tr><tr><td>Ligaclips</td><td>Ethicon</td><td>MSC20</td><td>Surgical Staples for LIMA takedown</td></tr><tr><td>Sterile Saline 20 mL</td><td>Fisher Scientific</td><td>20T700220</td><td>Flush for IV catheters</td></tr><tr><td>Telazol 100 mg/mL</td><td>Fort Dodge</td><td>01L60030</td><td>Pre operative Sedative</td></tr><tr><td>Triple Antibiotic Ointment</td><td>Johnson &amp;amp; Johnson</td><td>23734</td><td>Topical over wound</td></tr><tr><td>6.0 mm ID endotracheal tube</td><td>Mallinckrodt</td><td>86049</td><td>Establish airway for Revasc,MRI and Termination</td></tr><tr><td>1&quot; medical tape</td><td>Medline</td><td>MMM15271Z</td><td>Secure wound dressing and IV catheters</td></tr><tr><td>4.0 mm ID endotracheal tube</td><td>Medline</td><td>DYND43040</td><td>Establish airway for Hibernation</td></tr><tr><td>4.5 mm ID endotracheal tube</td><td>Medline</td><td>DYND43045</td><td>Establish airway for Hibernation</td></tr><tr><td>5.0 mm ID endotracheal tube</td><td>Medline</td><td>DYND43050</td><td>Establish airway for Hibernation</td></tr><tr><td>6.5 mm ID endotracheal tube</td><td>Medline</td><td>DYND43065</td><td>Establish airway for Revasc,MRI and Termination</td></tr><tr><td>7.0 mm ID endotracheal tube</td><td>Medline</td><td>DYND43070</td><td>Establish airway for Revasc,MRI and Termination</td></tr><tr><td>Bair Hugger Blanket -&amp;nbsp; Large size, underbody</td><td>Medline</td><td>AUG55501</td><td>Patient Warming system</td></tr><tr><td>Basic pack</td><td>Medline</td><td>DYNJP1000</td><td>Sterile drapes and table cover</td></tr><tr><td>Bone Wax</td><td>Medline</td><td>ETHW31G</td><td>Hemostasis of cut bone</td></tr><tr><td>Suction&amp;nbsp; tubing</td><td>Medline</td><td>DYND50223</td><td></td></tr><tr><td>Suction Container&amp;nbsp;</td><td>Medline</td><td>DYNDCL03000</td><td></td></tr><tr><td>1 mL Syringe</td><td>Medtronic/Covidien</td><td>1188100777</td><td>Administer injectable agents</td></tr><tr><td>12 mL Syringe</td><td>Medtronic/Covidien</td><td>8881512878</td><td>Administer injectable agents</td></tr><tr><td>20 mL Syringe</td><td>Medtronic/Covidien</td><td>8881520657</td><td>Administer injectable agents</td></tr><tr><td>3 mL Syinge</td><td>Medtronic/Covidien</td><td>1180300555</td><td>Administer injectable agents</td></tr><tr><td>6&amp;nbsp; mL Syringe</td><td>Medtronic/Covidien</td><td>1180600777</td><td>Administer injectable agents</td></tr><tr><td>60 mL Syringe</td><td>Medtronic/Covidien</td><td>8881560125</td><td>Administer injectable agents</td></tr><tr><td>Blower Mister Kit</td><td>Medtronic/Covidien</td><td>22120</td><td>Clears surgical field for vessel anastomosis</td></tr><tr><td>Roncuronium</td><td>Mylan</td><td>67457-228-05</td><td>Neuromuscular blocking agent</td></tr><tr><td># 40 clipper blade</td><td>Oster</td><td>078919-016-701</td><td>Remove hair from surgery sites</td></tr><tr><td>Hair Clipper</td><td>Oster</td><td>078566-011-002</td><td>Remove hair from surgery sites</td></tr><tr><td>Bupivicaine</td><td>Pfizer</td><td>00409-1161-01</td><td>Local Anesthetic</td></tr><tr><td>Cephazolin</td><td>Pfizer</td><td>00409-0805-01</td><td>Antibiotic</td></tr><tr><td>Heparin&amp;nbsp;</td><td>Pfizer</td><td>&amp;nbsp;0409-2720-03</td><td>anticoaggulant</td></tr><tr><td>Lidocaine 2%</td><td>Pfizer</td><td>00409-4277-01</td><td>Local Anesthetic/ antiarrthymic</td></tr><tr><td>Succinylcholine 20 mg/mL</td><td>Pfizer</td><td>00409-6629-02</td><td>Neuromuscular blocking agent</td></tr><tr><td>Anesthesia Monitor</td><td>Phillips&amp;nbsp; Intellivue&amp;nbsp;</td><td>MP70&amp;nbsp;</td><td>Supports ventilation with inhalant</td></tr><tr><td>Artificial Tears</td><td>Rugby</td><td>0536-1086-91</td><td>Lubricate eyes to prevent corneal drying</td></tr><tr><td>Buprenorphine 0.3 mg/mL</td><td>Sigma Aldrich</td><td>B9275</td><td>Pre operative Analgesic for survivial procedures</td></tr><tr><td>Isoflurane</td><td>Sigma Aldrich</td><td>CDS019936</td><td>General Anesthestic- Inhalant</td></tr><tr><td>36&amp;rdquo; Pressure monitoring tubing</td><td>Smith&amp;rsquo;s Medical</td><td>MX563</td><td>Connect art. Line&amp;nbsp; to transducer</td></tr><tr><td>48&amp;rdquo; Pressure monitoring tubing</td><td>Smith&amp;rsquo;s Medical</td><td>MX564</td><td>Connect art. Line&amp;nbsp; to transducer</td></tr><tr><td>Jelco 18 ga IV catheter&amp;nbsp;</td><td>Smiths medical</td><td>4054</td><td>IV access in Revasc, MRI and Term</td></tr><tr><td>Jelco 20 ga IV catheter</td><td>Smiths medical</td><td>4059</td><td>IV access in the MRI</td></tr><tr><td>Jelco 22 ga&amp;nbsp; IV catheter</td><td>Smiths medical</td><td>4050</td><td>IV access in Hibernation Procedure</td></tr><tr><td>OPVAC Synergy II</td><td>Terumo Cardiovascular System</td><td>401-230</td><td>Heart positioner and Stabilizer</td></tr><tr><td>Sternal Saw/ Necropsy Saw</td><td>Thermo Fisher</td><td>812822</td><td>Used to open chest cavity</td></tr><tr><td>Delrin Constrictor</td><td>U of MN</td><td>Custom made</td><td>Creates stenosis of LAD</td></tr><tr><td>Oxygen Tank E cylinder</td><td>various</td><td>various</td><td>Used for Blower Mister if anesthesia machine doesn&#039;t have auxiliary flow meter</td></tr><tr><td>Pressure Transducer</td><td>various</td><td>Must adapt to anesthesia monitor</td><td>Monitor direct arterial pressures</td></tr><tr><td>Xylazine 100 mg/mL</td><td>Vedco</td><td>468RX</td><td>Pre operative Sedative/ analgesic</td></tr></tbody></table>

surgical swine model of chronic cardiac ischemia treated by off-pump coronary artery bypass graft surgery

Chronic cardiac ischemia that impairs cardiac function, but does not result in infarct, is termed hibernating myocardium (HM). A large clinical subset of coronary artery disease (CAD) patients have HM, which in addition to causing impaired function, puts them at higher risk for arrhythmia and future cardiac events. The standard treatment for this condition is revascularization, but this has been shown to be an imperfect therapy. The majority of pre-clinical cardiac research focuses on infarct models of cardiac ischemia, leaving this subset of chronic ischemia patients largely underserved. To address this gap in research, we have developed a well-characterized and highly reproducible model of hibernating myocardium in swine, as swine are ideal translational models for human heart disease. In addition to creating this unique disease model, we have optimized a clinically relevant treatment model of coronary artery bypass surgery in swine. This allows us to accurately study the effects of bypass surgery on heart disease, as well as investigate additional or alternate therapies. This model surgically induces single vessel stenosis by implanting a constrictor on the left anterior descending (LAD) artery in a young pig. As the pig grows, the constrictor creates a gradual stenosis, resulting in chronic ischemia with impaired regional function, but preserving tissue viability. Following the establishment of the hibernating myocardium phenotype, we perform off-pump coronary artery bypass graft surgery to revascularize the ischemic region, mimicking the gold-standard treatment for patients in the clinic.

Following the initial hibernation surgery, stenosis greater than 70% should be able to be observed by clinical imaging techniques such as angiography or cardiac MRI (Figure 1A). 8 weeks following the surgical application of the LAD constrictor, analysis of regional function by ECHO or cardiac MRI reveals reduced function under increased workload (Figure 2). This can be tested by stimulating the heart with dobutamine (5mg/kg/min), and measuring circumferential strain and regional wall thickening. PET imaging demonstrates decreased blood flow and increased glucose uptake in the hibernating region as compared to the non-LAD territory within the same heart, indicating that the ischemic tissue remains viable. This enhancement in glucose uptake relative to blood perfusion is known as the &#34;flow-metabolism mismatch&#34; and mimics clinical findings of chronically hibernating myocardium4. There is no evidence of infarct by any imaging technique. If an infarct in the LAD region is present, the constrictor was too tight and created a full occlusion of the artery. If no regional abnormalities are evident, a hibernating phenotype has not been achieved.
Following successful coronary artery bypass surgery, animals may show incremental improvements in regional cardiac function both at rest and under inotropic stimulation with dobutamine, though these improvements will not restore function back to normal levels (Figure 3). Successful bypass surgery will eliminate the mortality risk associated with HM (Figure 4). The patent graft can be visualized by either angiography or cardiac MRI (Figure 1B). At necropsy, the LAD stenosis and LIMA patency is confirmed using sized coronary dilators. Myocardium is inspected to confirm viable tissue is present in all regions with infarction.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57229/57229fig1.jpg" /> 
Figure 1. Cardiac MRI images of stenosis and bypass graft. Cardiac MRI visualizes A) the LAD stenosis following constrictor placement, and B) the LIMA-LAD graft following coronary artery bypass surgery. This figure has been adapted from Hocum Stone, et al.9. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57229/57229fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57229/57229fig2.jpg" /> 
Figure 2. Cardiac MRI measurement of percent wall thickening. Measurement of wall thickening % by cardiac MRI shows impairment of regional function in hibernating regions of the left ventricle. Wall thickening % is significantly decreased in hibernating animals both at rest and under dobutamine infusion as compared to remote regions. Bypassed animals showed improvement in wall thickening % both at rest and under dobutamine infusion. (*=p&#60; 0.05;**=p&#60;0.01 ***=p&#60;0.001) (Hibernation n=12; 1 month revasc n=4; 3 months revasvc n=5) This figure has been adapted from Hocum Stone, et al.9. Data are presented as mean &#177; SEM. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57229/57229fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57229/57229fig3.jpg" /> 
Figure 3. Regional functional deficit remains present following bypass surgery. Echocardiogram performed 4 weeks following revascularization of hibernating myocardium shows regional functional deficit under inotropic stimulation following bypass surgery. (n=5) Data are presented as mean &#177; SEM. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57229/57229fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57229/57229fig4.jpg" /> 
Figure 4. Effect of bypass surgery on mortality in HM. Surgical revascularization eliminates mortality risk associated with HM. (Bypass n=18; hibernation n=48). This figure has been adapted from Holley, et al.15 <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57229/57229fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery at JoVE.com

Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery

This protocol presents a surgical large animal model of chronic, single vessel ischemia that results in regional abnormalities but does not create infarct, known as hibernating myocardium. Following establishment of chronic ischemia, animals are treated with off-pump LIMA-LAD coronary artery bypass graft surgery to revascularize the ischemic tissue.

Chronic cardiac ischemia that impairs cardiac function, but does not result in infarct, is termed hibernating myocardium (HM). A large clinical subset of ...

surgical-swine-model-chronic-cardiac-ischemia-treated-off-pump

Nanyang Technological University

Research

JoVE Journal

Medicine

9.4K Views.  University of Minnesota. Dit protocol biedt een chirurgische grote diermodel van chronische, één vaartuig ischemie die resulteert in regionale afwijkingen, maar maakt geen infarct, bekend als winterslaap myocard. Na totstandkoming van chronische ischemie, dieren worden behandeld met off-pomp LIMA-LAD coronaire bypass prothese chirurgie te revascularize de ischemische weefsel.

Video: Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery

A Swine Model of Neonatal Asphyxia

Annually more than 1 million neonates die worldwide as related to asphyxia. Asphyxiated neonates commonly have multi-organ failure including hypotension, perfusion deficit, hypoxic-ischemic encephalopathy, pulmonary hypertension, vasculopathic enterocolitis, renal failure and thrombo-embolic complications. Animal models are developed to help us understand the patho-physiology and pharmacology of neonatal asphyxia. In comparison to rodents and newborn lambs, the newborn piglet has been proven to be a valuable model. The newborn piglet has several advantages including similar development as that of 36-38 weeks human fetus with comparable body systems, large body size (&tilde;1.5-2 kg at birth) that allows the instrumentation and monitoring of the animal and controls the confounding variables of hypoxia and hemodynamic derangements.
We here describe an experimental protocol to simulate neonatal asphyxia and allow us to examine the systemic and regional hemodynamic changes during the asphyxiating and reoxygenation process as well as the respective effects of interventions. Further, the model has the advantage of studying multi-organ failure or dysfunction simultaneously and the interaction with various body systems. The experimental model is a non-survival procedure that involves the surgical instrumentation of newborn piglets (1-3 day-old and 1.5-2.5 kg weight, mixed breed) to allow the establishment of mechanical ventilation, vascular (arterial and central venous) access and the placement of catheters and flow probes (Transonic Inc.) for the continuously monitoring of intra-vascular pressure and blood flow across different arteries including main pulmonary, common carotid, superior mesenteric and left renal arteries. Using these surgically instrumented piglets, after stabilization for 30-60 minutes as defined by Z&lt;10% variation in hemodynamic parameters and normal blood gases, we commence an experimental protocol of severe hypoxemia which is induced via normocapnic alveolar hypoxia. The piglet is ventilated with 10-15% oxygen by increasing the inhaled concentration of nitrogen gas for 2h, aiming for arterial oxygen saturations of 30-40%. This degree of hypoxemia will produce clinical asphyxia with severe metabolic acidosis, systemic hypotension and cardiogenic shock with hypoperfusion to vital organs. The hypoxia is followed by reoxygenation with 100% oxygen for 0.5h and then 21% oxygen for 3.5h. Pharmacologic interventions can be introduced in due course and their effects investigated in a blinded, block-randomized fashion.

Large animal models have good translational values in the examination of physiology and pharmacology of neonatal asphyxia. Using newborn piglets, we develop an experimental protocol to simulate neonatal asphyxia which has advantages of studying the systemic and regional hemodynamics, oxygen transport with biochemical and pathologic pathways and correlations.

Annually more than 1 million neonates die worldwide as related to asphyxia. Asphyxiated neonates commonly have multi-organ failure including hypotension, ...

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 ...

Implantation of Inferior Vena Cava Interposition Graft in Mouse Model

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are often used for reconstructive surgery to treat congenital cardiac anomalies. The long-term clinical results showed excellent patency rates, however, with significant incidence of stenosis. To investigate the cellular and molecular mechanisms of vascular neotissue formation and prevent stenosis development in tissue engineered vascular grafts (TEVGs), we developed a mouse model of the graft with approximately 1 mm internal diameter. First, the TEVGs were assembled from biodegradable tubular scaffolds fabricated from a polyglycolic acid nonwoven felt mesh coated with &#949;-caprolactone and L-lactide copolymer. The scaffolds were then placed in a lyophilizer, vacuumed for 24 hr, and stored in a desiccator until cell seeding. Second, bone marrow was collected from donor mice and mononuclear cells were isolated by density gradient centrifugation. Third, approximately one million cells were seeded on a scaffold and incubated O/N. Finally, the seeded scaffolds were then implanted as infrarenal vena cava interposition grafts in C57BL/6 mice. The implanted grafts demonstrated excellent patency (&#62;90%) without evidence of thromboembolic complications or aneurysmal formation. This murine model will aid us in understanding and quantifying the cellular and molecular mechanisms of neotissue formation in the TEVG.

To improve our knowledge of cellular and molecular neotissue formation, a murine model of the TEVG was recently developed. The grafts were implanted as infrarenal vena cava interposition grafts in C57BL/6 mice. This model achieves similar results to those achieved in our clinical investigation, but over a far shortened time-course.

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are often used for reconstructive surgery to treat congenital cardiac anomalies. ...

Evaluation of a Novel Laser-assisted Coronary Anastomotic Connector - the Trinity Clip - in a Porcine Off-pump Bypass Model

To simplify and facilitate beating heart (i.e., off-pump), minimally invasive coronary artery bypass surgery, a new coronary anastomotic connector, the Trinity Clip, is developed based on the excimer laser-assisted nonocclusive anastomosis technique. The Trinity Clip connector enables simplified, sutureless, and nonocclusive connection of the graft to the coronary artery, and an excimer laser catheter laser-punches the opening of the anastomosis. Consequently, owing to the complete nonocclusive anastomosis construction, coronary conditioning (i.e., occluding or shunting) is not necessary, in contrast to the conventional anastomotic technique, hence simplifying the off-pump bypass procedure. Prior to clinical application in coronary artery bypass grafting, the safety and quality of this novel connector will be evaluated in a long-term experimental porcine off-pump coronary artery bypass (OPCAB) study. In this paper, we describe how to evaluate the coronary anastomosis in the porcine OPCAB model using various techniques to assess its quality. Representative results are summarized and visually demonstrated.

This paper describes a novel nonocclusive coronary anastomotic connector in a porcine off-pump coronary artery bypass (OPCAB) model. This easy-to-use coronary connector has intrinsic potential to facilitate minimally invasive OPCAB surgery.

To simplify and facilitate beating heart (i.e., off-pump), minimally invasive coronary artery bypass surgery, a new coronary anastomotic connector, the ...

A Chronic Cardiac Ischemia Model in Swine Using an Ameroid Constrictor

Cardiovascular disease remains the number one cause of mortality in the United States. There are numerous approaches to treating these diseases, but regardless of the approach, an in vivo model is needed to test each treatment. The pig is one of the most used large animal models for cardiovascular disease. Its heart is very similar in anatomy and function to that of a human. The ameroid placement technique creates an ischemic area of the heart, which has many useful applications in studying myocardial infarction. This model has been used for surgical research, pharmaceutical studies, imaging techniques, and cell therapies.
There are several ways of inducing an ischemic area in the heart. Each has its advantages and disadvantages, but the placement of an ameroid constrictor remains the most widely used technique. The main advantages to using the ameroid are its prevalence in existing research, its availability in various sizes to accommodate the anatomy and size of the vessel to be constricted, the surgery is a relatively simple procedure, and the post-operative monitoring is minimal, since there are no external devices to maintain. This paper provides a detailed overview of the proper technique for the placement of the ameroid constrictor.

The purpose of this protocol is to demonstrate the placement of a delayed constricting device (an ameroid constrictor) around a coronary artery in a swine model. This device creates an ischemic area of the heart that is useful for studying new diagnostic imaging techniques and new methods of treatment.

Cardiovascular disease remains the number one cause of mortality in the United States. There are numerous approaches to treating these diseases, but ...

A Pre-Clinical Porcine Model of Orthotopic Heart Transplantation

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart failure. Multiple small-animal models of heart transplantation have been used to study the acute and long-term effects of novel therapies. However, few are tested and demonstrated success in clinical trials. It is of critical importance to evaluate new therapies in a clinically relevant large-animal model for efficient and reliable translation of basic studies&#39;&#160;findings. Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and previously used to investigate novel cardioprotective strategies. This procedure focuses on acute ischemia-reperfusion injury and is a reliable method to investigate novel interventions which have been tested and validated in smaller experimental models, such as the murine model. We demonstrate its usefulness in assessing cardiac performance during the early post-transplantation period and other potential possibilities enabled by the model.

Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and utilized to investigate novel cardioprotective strategies.

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart ...

Establishment and Evaluation of a Porcine Vein Graft Disease Model

Venous graft disease (VGD) is the leading cause of coronary artery bypass graft (CABG) failure. Large animal models of CABG-VGD are needed for the investigation of disease mechanisms and the development of therapeutic strategies. 
To perform the surgery, we enter the cardiac chamber through the third intercostal space and carefully dissect the internal mammary vein and immerse it in normal saline. The right main coronary artery is then treated for ischemia. The target vessel is incised, a shunt plug is placed, and the distal end of the graft vein is anastomosed. The ascending aorta is partially blocked, and the proximal end of the graft vein is anastomosed after perforation. The graft vein is checked for patency, and the proximal right coronary artery is ligated. 
CABG surgery is performed in minipigs to harvest the left internal mammary vein for its use as a vascular graft. Serum biochemical tests are used to evaluate the physiological status of the animals after surgery. Ultrasound examination shows that the proximal, middle, and distal end of the graft vessel are unobstructed. In the surgical model, turbulent blood flow in the graft is observed upon histological examination after the CABG surgery, and venous graft stenosis associated with intimal hyperplasia is observed in the graft. The study here provides detailed surgical procedures for the establishment of a repeatable CABG-induced VGD model.

In this protocol, novel pig vein bypass grafting was performed through a small incision in the left chest wall without cardiopulmonary bypass. A postoperative pathology study was done, which showed intimal thickening.

Venous graft disease (VGD) is the leading cause of coronary artery bypass graft (CABG) failure. Large animal models of CABG-VGD are needed for the ...

Extracorporeal Cardiopulmonary Resuscitation in Animal Model After Cardiac Arrest

Pediatric Animal Model of Extracorporeal Cardiopulmonary Resuscitation After Prolonged Circulatory Arrest

Congenital heart disease (CHD) is the most prevalent congenital malformation, with about one million births impacted worldwide per year. Comprehensive investigation of this disease requires appropriate and validated animal models. Piglets are commonly used for translational research due to their analogous anatomy and physiology. This work aimed to describe and validate a neonatal piglet model of cardiopulmonary bypass (CPB) with circulatory and cardiac arrest (CA) as a tool for studying severe brain damage and other complications of cardiac surgery. In addition to including a list of materials, this work provides a roadmap for other investigators to plan and execute this protocol. After experienced practitioners performed several trials, the representative results of the model demonstrated a 92% success rate, with failures attributed to small piglet size and variant vessel anatomy. Furthermore, the model allowed practitioners to select from a wide variety of experimental conditions, including varying times in CA, temperature alterations, and pharmacologic interventions. In summary, this method uses materials readily available in most hospital settings, is reliable and reproducible, and can be widely employed to enhance translational research in children undergoing heart surgery.

Author Spotlight: Simulating Pediatric Cardiac Surgery Using a Neonatal Piglet Model

This protocol describes a neonatal porcine model of cardiopulmonary bypass (CPB), with circulatory and cardiac arrest as a tool for studying severe brain damage and other complications secondary to CPB.

Congenital heart disease (CHD) is the most prevalent congenital malformation, with about one million births impacted worldwide per year. Comprehensive ...

Adjunctive Exosome Therapy: Enhancing Myocardial Recovery Post-CABG Surgery

Surgical Porcine Model of Chronic Myocardial Ischemia Treated by Exosome-laden Collagen Patch and Off-pump Coronary Artery Bypass Graft

Chronic myocardial ischemia resulting from progressive coronary artery stenosis leads to hibernating myocardium (HIB), defined as myocardium that adapts to reduced oxygen availability by reducing metabolic activity, thereby preventing irreversible cardiomyocyte injury and infarction. This is distinct from myocardial infarction, as HIB has the potential for recovery with revascularization. Patients with significant coronary artery disease (CAD) experience chronic ischemia, which puts them at risk for heart failure and sudden death. The standard surgical intervention for severe CAD is coronary artery bypass graft surgery (CABG), but it has been shown to be an imperfect therapy, yet no adjunctive therapies exist to recover myocytes adapted to chronic ischemia. To address this gap, a surgical model of HIB using porcine that is amenable to CABG and mimics the clinical scenario was used. The model involves two surgeries. The first operation involves implanting a 1.5 mm rigid constrictor on the left anterior descending (LAD) artery. As the animal grows, the constrictor gradually causes significant stenosis resulting in reduced regional systolic function. Once the stenosis reaches 80%, the myocardial flow and function are impaired, creating HIB. An off-pump CABG is then performed with the left internal mammary artery (LIMA) to revascularize the ischemic region. The animal recovers for one month to allow for optimal myocardial improvement prior to sacrifice. This allows for physiologic and tissue studies of different treatment groups. This animal model demonstrates that cardiac function remains impaired despite CABG, suggesting the need for novel adjunctive interventions. In this study, a collagen patch embedded with mesenchymal stem cell (MSC)-derived exosomes was developed, which can be surgically applied to the epicardial surface distal to LIMA anastomosis. The material conforms to the epicardium, is absorbable, and provides the scaffold for the sustained release of signaling factors. This regenerative therapy can stimulate myocardial recovery that does not respond to revascularization alone. This model translates to the clinical arena by providing means of physiological and mechanistic explorations regarding recovery in HIB.

Author Spotlight: Enhancing Coronary Artery Revascularization

This study presents a surgical porcine model of chronic myocardial ischemia due to progressive coronary artery stenosis, resulting in impaired cardiac function without infarction. Following ischemia, animals undergo off-pump coronary artery bypass graft with epicardial placement of stem cells-derived exosomes-laden collagen patch. This adjunctive therapy improves myocardial function and recovery.

Chronic myocardial ischemia resulting from progressive coronary artery stenosis leads to hibernating myocardium (HIB), defined as myocardium that adapts ...

Ascending Aortic Banding for Studying Pressure-Overload Induced Heart Failure

A Minimally Invasive Model of Aortic Stenosis in Swine

Large animal models of heart failure play an essential role in the development of new therapeutic interventions due to their size and physiological similarities to humans. Efforts have been dedicated to creating a model of pressure-overload induced heart failure, and ascending aortic banding while still supra-coronary and not a perfect mimic of aortic stenosis in humans, closely resembling the human condition.
The purpose of this study is to demonstrate a minimally invasive approach to induce left ventricular pressure overload by placing an aortic band, precisely calibrated with percutaneously introduced high-fidelity pressure sensors. This method represents a refinement of the surgical procedure (3Rs), resulting in homogenous trans-stenotic gradients and reduced intragroup variability. Additionally, it enables swift and uneventful animal recovery, leading to minimal mortality rates. Throughout the study, animals were followed for up to 2 months after surgery, employing transthoracic echocardiography and pressure-volume loop analysis. However, longer follow-up periods can be achieved if desired. This large animal model proves valuable for testing new drugs, particularly those targeting hypertrophy and the structural and functional alterations associated with left ventricular pressure overload.

Author Spotlight: Development of a Minimally Invasive Large-Animal Model for Reliable and Reproducible Cardiovascular Research 

This protocol describes a minimally invasive surgical procedure for ascending aortic banding in swine.

Large animal models of heart failure play an essential role in the development of new therapeutic interventions due to their size and physiological ...

Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery

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