This method can help answer key questions about underlying mechanisms and treatment of right ventricular failure. The main advantage of this technique is that it allows a precise and reproducible afterload increase that induces right ventricular hypertrophy and failure. The implications of this technique extend toward the the therapy of right ventricular failure, because it eliminates effects secondary to pulmonary vasodilation.
Before beginning the trunk isolation procedure select an appropriate diameter for the banding and adjust the ligating clip applier until the distance between the jaws is one millimeter when the clip is fully compressed leaving a lumen of 6 millimeters. Next, confirm a lack of response in toe pinch in an anesthetized 100 to 120-gram Wistar rat weanling and make a two-centimeter skin incision along the midline of the sternum. Under a dissecting microscope cut the major pectoral muscle at its sternal attachment and identify the second, third, and fourth costae.
Use a pair of scissors to cut the fourth, third, and second costae close to the sternum and carefully dissect the intercostal muscles until a complete left thoracotomy has been performed. When performing the left lateral thoracotomy you should be very careful as the left internal mammorial artery is just bellow the ribcage, so be very careful. Insert a retractor between the sternum and the costae and open the jaws until the thymus is visible at the top of the viewing field.
Use the peen forceps to carefully flip the thymus to expose the aorta and the pulmonary trunk and guide the tip of a small surgical hooklet, bent to an 85 degree angle, through the reverse paracardial sinus behind the left atrial appendage. Pull the hooklet halfway back through the sinus and guide the tip of the ear hook upward until it appears between the ascending aorta, and the pulmonary trunk. When placing the ear hook make sure you have the right angle.
you shouldn't use any force it might be a bit difficult initially but you can master it with practice. Use iris scissors to remove any connective tissue covering the tip to separate the pulmonary trunk from the ascending aorta. Use angled foreceps to guide a 10 centimeter piece of 4/0 multifilimant ligature around the pulmonary trunk through the passage made by the hook.
Seize the end of the ligature with another forceps. The pulmonary trunk should now be separated from the ascending aorta and can be controlled by the ligature around it. When the pulmonary trunk has been secured, use a clip to load the adjusting ligating clip applier.
Carefully guide one jaw and one leg of the clip through the passage around the pulmonary trunk using the ligature to gently pull the pulmonary trunk up and into the fork of the clip. When the pulmonary trunk is in the fork, and the two tips of the clip are free of any connective tissue, compress the clip to apply the banding removing the ligature as soon as the right ventricle dilates in response to the banding. When the trunk has been banded remove the peen forceps from the thymus and return the tissue to it's natural position.
Remove the retractor, and use absorbable 4/0 multifiliment sutures to close the thorax in three layers. Then subcutaneously inject 2 milliliters of saline to replace any fluid lost during the surgery and monitor the animal until full recumbency. Selecting different diameters of the clip it is possible to induce different stages of disease severity, as evident here by an increasing degree of right ventricular hypertrophy.
Only severe banding causes extra cardiac manifestations including liver failure. Differences in moderate versus severe pulminary trunk banding are evident by increasing right ventricular pressure and cause moderate versus severe right ventricular failure as revealed by a stepwise decrease in cardiac output and tricuspid annular plane systolic excursion as the severity of the banding increases. Pulmonary trunk banding procedure induced right ventricle dilation is evident by an increase in both right ventricular end diastolic volume and in systolic volume in the moderate pulmonary trunk banded rats compared to sham-operated animals, and in the severe pulmonary trunk banded rats compared to both the moderate and sham animals.
A stepwise decrease in right ventricular ejection fraction is also observed. Right ventricular hypertrophy is further indicated by an increase in cardiomyocyte cross sectional area in pulmonary trunk banded rats, compared to sham-operated animals as well as other morphological changes to the right ventricle associated with right ventricle failure, including right ventricle fibrosis. Once mastered this technique can be performed in 30 minutes if it's performed properly.
While attempting this procedure it's important to obtain consistent results with the model before initiating experimental research. After its development this technique paved the way for researchers in the field of right heart failure to explore pharmacologic interventions and basic mechanisms. After watching this video you should have a good understanding on how to perform pulmonary trunk banding.
