More than half of heart failure cases worldwide are classified as heart failure with preserved blood ejection fraction or HFpEF. This video presents a step by statist procedure to model HFpEF minipigs as well as echocardiography techniques for assessing cardiac function. This model has a single predisposing filter.
There is aortic constriction, induced pressure overload. Hence, the model is helpful for studying a certain type of HFpEF. In addition to surgical technique per operation planning, animal quality control and post-operation animal care are critical steps.
The biochemical tests and electrocardiography help in monitoring animal health and changes in her structure and function. Xiaohui Li, a clinical cardiac surgeon. Weijiang Tan, a trained animal surgeon.
Xiang Li, a trained anesthetist for this operation. Shuang Chen, a trained operating room nurse. And Honghua Chen, a trained operating room nurse will be demonstrating the procedure.
To begin acclimatize the animals to the facility for 14 days before surgery. Prepare the surgical room and devices. Restrain and place the minipig in the right lateral recumbent position on the operating surgery table.
Turn on the heating system to maintain the body temperature of the animal. Perform the echocardiography and collect a two milliliter blood sample. Initiate the ventilation at eight milliliters per kilograms of tidal volume and 30 breaths per minute.
Establish intravenous cannulation using a peripheral intravenous catheter from an ear vein. Then connect the animal to a veterinary monitor. Shave the left thoracic area.
Apply 0.7%iodine and 75%alcohol to aseptically prepare the skin from the scapula to the diaphragm. Place sterile drapes over the surgical area. Mark approximately a 15 centimeter long incision along the fourth intercostal space.
Then make the skin incision using electrocautery. Open the chest using a combination of cautery and blunt dissection of the muscle and connective tissue. Use a rib retractor to spread the ribs.
Locate the thoracic descending aorta segment and determine the constriction site and use two three OTT surgical sutures to loop around the segment twice. Set up pressure measurement units. To determine the degree of constriction, tighten the surgical suture surrounding the descending aorta segment gradually to achieve the desired constriction degree.
Allow the pressure readings to stabilize for 20 minutes and permanently tighten the surgical knots. Use a drainage chest tube to evacuate the air and excess fluids in the chest cavity. Monitor the presence of eye blinking and limb movement of the animal.
Disconnect the ventilator, but leave the endotracheal tube and monitor the presence of spontaneous breathing. Place the animal in a mobile restraint unit with a canvas cover. Shave the left chest of the animal.
Place fingers on the left center of the chest to feel the epical pulse. Apply the ultrasonic gel to the surrounding area. Place the ultrasound system's phased array transducer in the third intercostal space.
Move the transducer toward an anterior or posterior direction and adjust the notch angle. Identify the atria, ventricles and aorta and record the B mode and M mode perasternal long axis images. Next in the parasternal short axis view, identify the interventricular septum, left ventricular posterior wall and papillary muscle, and record the B mode and M mode images.
Use the workstation provided by the manufacturer of the ultrasound system to assess the cardiac structure and function. The cardiac structure and function evaluation showed the displayed B mode and M mode recordings of the perasternal short axis. The ventricular septum thickness increased in the descending aortic constriction hearts, whereas the posterior wall thickness increased and then decreased during the observation period, suggesting the hypertrophic remodeling in the left ventricle of the descending aortic constriction minipigs.
The left ventricular internal dimension at end diastole decreased in weeks four and six, and then gradually increased after week eight, suggesting that the ventricles underwent concentric hypertrophy before dilation. The left ventricular ejection fraction of the model hearts was maintained at more than 50%during the 12 weeks. Compared with sham hearts, enlargement of the descending aortic constriction hearts was observed.
The heart failure marker, cardiac troponin I, was significantly higher at weeks 4, 8 and 12 in the descending aortic constriction group than in the sham group at the corresponding time points. Cardiomyocytes in the atria ventricular septum and ventricles displayed hypertrophy with pignosis. Muscular layers were reduced in endometrial valve and vascular endothelial hyperplasia was observed in the aorta.
Moreover, descending aortic constriction induced extensive fibrosis in the myocardium of the minipigs, accompanied by infiltration of inflammatory cells in the left ventricles, right atrium, and aortic walls. This model is a powerful tool to study tissues damage, fibrosis, inflammation, and concentric dysfunction in pressure overload induced HFpEF.
