The overall goal of the following experiment is to assess the efficacy of new therapeutic strategies for ischemic heart disease. In a pig model, with left anterior descending artery occlusion as a first step, the internal carotid artery is cannulated for arterial access. Then a catheter is advanced through the aorta and placed at the osteum of the left main coronary artery, which allows a smaller guide wire to be positioned in the left anterior descending or LAD artery.
Next, the G wire is used to guide an intra coronary balloon catheter into the LAD, and the balloon is inflated for 90 minutes blocking all blood flow. After the second diagonal branch, the results show that the cardiac systolic function has declined, that there is subsequent adverse remodeling of the left ventricle and that there is substantial scar tissue from the infarct. Here, the Department of Cardiology at the, we bring together different disciplines, engineers and industrial partners to create innovative therapies to really advance treatment of our patients.
A reproducible large animal model of myocardial infarction enables us to validate new investigational therapies such as cardiac stem cell therapy and to test its safety and efficacy in pigs that closely resemble the human heart. In terms of size and hemodynamics, The model we have developed will help us to address key issues in the field of cardiac regenerative medicine. By testing new compounds in a large animal model, we will bridge the gap between basic research and clinical practice.
Translational research is crucial for obtaining new mechanistic insights and for bringing new promising therapies. One step closer to clinical application Following sedation and anesthesia, place the pig on a ventilator and prepare the animal as described in the text protocol. To obtain a baseline echocardiogram, place the animal in the right lateral position.
Orient and obtain a parasternal long axis view in 2D mode, and determine the left ventricular dimensions at end diastole and end systole. In M mode, rotate the echo probe 90 degrees clockwise while maintaining its sternal position to acquire the left ventricular short axis views of the mitral valve and tilt the probe to gain views at the levels of the papillary muscle and apex. Optionally, place the echo probe one or two intercostal spaces lower after disinfecting the surgical areas with 2%iodine drape the non-sterile areas with sterile surgical drapes.
Begin the surgery with a 15 centimeter medial incision in the neck, cut along and beyond the linear alba. To minimize muscle damage and bluntly, approach the carotid artery and internal jugular vein next to the trachea. Carefully isolate the carotid artery and internal jugular vein.
Being careful not to damage the vagal nerve. Place Vicryl two OTT sutures around both vessels to gain vessel control. Then cannulate the jugular vein with a nine French sheath.
Using the Seldinger technique, make sure the vein is ligated before securing the sheath. Next, cannulate the internal carotid artery with an eight French sheath. Also, using the Seldinger technique, fix the sheath to the artery, making sure that the artery is not fully occluded by the suture.
The next step is to insert a swan gans catheter via the previously placed sheath into the internal jugular vein. Then connect a cardiac output device to the part of the swan gans that culminates in the proximal lumen. Now inject five milliliters of 0.9%saline into the proximal lumen of the swan gans, and measure cardiac output.
Repeat this two more times and average the indices. Next, calibrate the pressure volume loop system by using the previously determined cardiac output. Under fluoroscopic guidance.
Insert the seven French conductance catheter via the carotid artery into the left ventricle. After volume calibration is completed, induce apnea by turning off the respirator and record 10 to 15 beats under apnea. Then turn the respirator back on and remove the swan gans.
Next, use fluoroscopic guidance to place a balloon catheter in the inferior caval vein at the level of the diaphragm. After turning off the respirator, again, inflate the balloon and record the corresponding pressure volume loops to perform preload reduction. When finished, turn the respirator back on again.
For int coronary measurements, position an eight French guiding catheter in the osteum of the left coronary artery. Infuse 200 micrograms of nitroglycerin int coronary to prevent coronary spasms. Next, place the combined pressure flow wire in the proximal part of the left coronary artery.
Then advance the wire to the mid part of the LAD. At this point, start measuring baseline pressure and flow. Then induce hyperemia by administering 60 micrograms of adenosine intra coronary.
Then flush with two milliliters of saline and commence hyperemic pressure and flow measurements. Allow the flow to return to baseline values and repeat the measurement twice. When finished with the measurements, remove the pressure flow wire from the LAD as a precaution.
Prior to inducing a myocardial infarction, insert the intracardiac defibrillation catheter in the right ventricle using the venous sheath. Place the distal electrodes in the apex of the right ventricle and the proximal electrodes in the atrium. Then connect the catheter to the defibrillator and set it to 50 joules.
Next, measure the diameter of the LAD distal from the second diagonal or D two branch in the AP and LAO 30 degrees view. Choose an angioplasty balloon with a diameter that is the same size or slightly larger than the diameter of the LAD distal from the D two position. A guide wire through the guiding catheter distally in the LAD, advance the balloon catheter over the G wire, placing the balloon distal from the D two.
After administering 30 IE per kilogram heparin inflate the balloon until the pressure matches the right diameter of the LAD. Next, use angiography to check that the LAD is totally occluded. Cover the sterile working field and the wound in the neck with sterile drapes.
Free the chest from any coverage to make it available for chest compressions or transthoracic defibrillation if the need should arise. After 90 minutes, check by angiography to ensure that the LAD is still fully occluded. Then administer another 30 IE per kilogram heparin and deflate the balloon.
After verifying reperfusion, remove the deflated balloon and the guiding catheter from the carotid sheath. Follow the instructions in the text protocol for postoperative care and MRI imaging and analysis. The 90 minute balloon occlusion of the LAD led to extensive myocardial damage and scar formation as shown by the white color visualized by TTC staining at the one month follow-up.
The schematic of the infarct distribution shows that the infarction is located in the anterior interseptal and infer septal segments of the heart in these short and long axis. Late gadolinium enhanced CMR images, the white signal indicated by the black arrowheads shows the extensive infarct scar localized in the anterior interseptal and infer septal segments of the heart. These CMR cine loop images at end diastole and systole show functional impairment of the infarct scar segments.
Echocardiographic M mode images of 2D para sternal long axis show left ventricular dilatation one month after myocardial infarction as indicated by the longer blue line in the lower image functional impairment is shown by the absence of septal thickening, intra coronary pressure and flow velocity recordings using the combo wire show high response to hyperemia prior to myocardial infarction. One month after myocardial infarction, the infarct related artery has a decreased hyperemic response in the coronary flow velocity. As a result, pressure and flow velocity derived parameters and flow velocity reserve are decreased compared to the baseline.
While attempting this procedure, it's particularly important to avoid Airbus getting trapped inside the catheter and syringes as they can act as air emboli leading to a permanent occlusion once injected in one of the coronary arteries. In our experience, you should wait a minimum of four weeks after the infarction if you would like to study chronic MI and progressive adverse remodeling. This protocol paces the way for researchers to explore new interventions and therapeutics in the field of ischemic heart disease in a model that closely resembles the human situation.
The techniques used in this protocol provide essential information on cardiac function, collagen content in the infarct, scar, coronary flow, and microvascular resistance. The techniques we have shown you today can be used as separate building blocks to design your own study design, for instance, you can use the functional endpoints, the histology, or even the microvascular resistance as separate endpoints in your study. Moreover, by timing the therapy, you can use these issues in acute myocardial infarction setting.
For instance, looking at reperfusion injury or looking at the long-term infection. The chronic myocardial infarction model in the use of stem cell therapy.
