This swine heart failure model, induced by left circumflex artery blockage and rapid pacing, can be used to assess the effects of direct intramyocardial stem cell injection on heart regeneration. Our swine colony heart failure model is quite stable. The new infarct size of this model is around 16%of left ventricle and left ventricle injection infarction reduced by at least 40%from baseline.
With the experimental pig fixed in the supine position, locate the right carotid artery and juggler vein in the carotid triangle, and use hemostatic forceps and aseptic technique to isolate the right carotid artery and jugular vein. Ligate the distal end of the right carotid artery and juggler vein and use an angiocath to cannulate the right juggler vein. After inserting a pacemaker lead into the right ventricle under x-ray guidance use forceps to isolate the sternocleidomastoid and anterior scalene muscles and connect the pacemaker to the lead.
Then implant a pacemaker between the two muscles. Then close the two muscles with 2-0 silk. To assess changes in left ventricle function, isolate the right femoral artery and femoral vein in the femoral triangle, and calculate the right femoral artery with an angiocath.
Place a guidewire into the femoral vein via the angiocath and remove the angiocath. Cannulate a 12 French sheath into the femoral vein under the guidance of the guidewire and remove the guidewire. Cannulate the right femoral artery with a nine French sheath as just demonstrated.
And insert a balloon catheter through the 12 French sheath into the interior vena cava under x-ray guidance. Calibrate a seven French pressure volume catheter in isotonic saline with a pressure volume signal processor and insert the catheter into the left ventricle apex through the nine French sheath under x-ray guidance. Suspend the ventilation and use the pressure volume signal processor to measure the left ventricle maximal and negative pressure derivative, and systolic pressure and end diastolic pressures.
Then restart the ventilation. For myocardial infarction induction, administer five milligrams per kilogram amiodarone and 1.5 milligrams per kilogram lidocaine bolus intravenously over one hour to prevent ventricular arrhythmias before calculating the right carotid artery with an eight French sheath as demonstrated. Perform the coronary angiography through a six French sheath over-the-wire guiding catheter via the placed sheath guided by standard C arm fluoroscopy.
Occlude to the left circumflex coronary artery distal to the first obtuse marginal branch with percutaneous transluminal coronary angioplasty dilation balloon catheter inflation under x-ray guidance. Load one milliliter of 700 micrometers sponge microspheres mixed with seven milliliters of iohexol in a 10 milliliter syringe and inject the mixture through the balloon catheter to block the left circumflex coronary artery. Then deflate the balloon and perform an angiogram to confirm the occlusion.
Eight weeks after infarction induction load two times 10 to the eighth human-induced pluripotent stem cell-derived mesenchymal stem cells in two milliliters of normal saline into a five milliliter syringe and sterilize 10 centimeters around the apex beat area of the anesthetized experimental animal. Use a retractor to perform a left thoracotomy at the four or five intercostal space and perform a pericardiotomy to expose the infarcted lateral wall. When the infarcted areas visible, perform five to eight intra myocardial injections of approximately 300 microliters of cells per injection before closing the intercostal space with iron wire and closing the muscle layer with 2-0 silk sutures and the subcutaneous tissues and skin layers with 2-0 vicryl sutures.
To assess the inducibility of ventricular tachyarrhythmia after cell therapy, insert a six French electrophysiological catheter into the right ventricular apex via the femoral vein and display the intracardiac recordings with the surface electrocardiogram leas I, II, and III on the electrophysiological recording system at a speed of 200 millimeters per second. Use a stimulator to deliver a two millisecond pulse width at two times the diastolic threshold and deliver a pacing train of eight stimuli at one 200 millisecond and one 300 millisecond drive cycle length followed by one or two premature extra stimuli. Then sequentially shortened the coupling intervals until the ventricular effective refractory period of arrhythmia is induced, noting the presence of an inducible sustained ventricular tachyarrhythmia.
In this representative experiment, serial echocardiographic examination showed that the left ventricle ejection fraction significantly decreased from baseline while the left ventricle end-diastolic dimension and end systolic dimension significantly increased at eight weeks after myocardial infarction induction. In contrast, the left ventricle ejection fraction significantly increased and the end systolic dimension remarkably decreased in the cell transplantation group eight weeks after administration. The negative pressure derivative and end systolic pressure volume relationship significantly decreased from baseline at eight weeks after induction of myocardial infarction while intramyocardial administration of mesenchymal stem cells resulted in an increase in these functions.
Measurement of the left ventricle infarct wall thickness in five to seven serial one centimeter thick sections from each animal revealed a percentage of left ventricle infarction of approximately 16%There was no cell survival around the injection site in the infarct area eight weeks after transplantation. But a small number of the surviving injected stem cells were visible in the periinfarct area. The incidents of inducible sustained ventricular tachyarrhythmias could be easily increased in animals with heart failure.
Of note, stem cell transplantation did not significantly modify the underlying myocardial substrate to reduce susceptibility to ventricular tachyarrhythmia. As left circumflex coronary artery blockage may induce arrhythmia. Be sure to monitor the ECG and to immediately use external biphasic defibrillator to re-establish sinuses as necessary.
This method provide a stable and reproducible clinically relevant large animal model of heart failure for testing the efficacy of stem cell-based therapies.
