Chronic Ovine Model of Right Ventricular Failure and Functional Tricuspid Regurgitation

The model is similar to those previously described in the literature. Although our specific goal was to induce significant functional tricuspid regurgitation rather than just isolated right heart dysfunction. The technique may be used in the future to study mechanisms of functional tricuspid regurgitation with its associated right ventricular annular and subular remodeling, as well as tissue changes.

The model may be helpful in identifying molecular pathways responsible for functional tricuspid regurgitation and establishing more efficient and complex surgical techniques for its treatment. Begin by placing the animal in a sheep chair. Shave the right anterior aspect of the neck around 10 to 15 centimeters lateral from the midline for the right jugular vein using clippers.

After disinfecting the surgical area, turn the animal's head to the left to expose the right anterior and lateral aspects of the neck. Then localize the jugular vein course by compressing the bottom of the neck to distend the vein. Now, anesthitize the insertion site with 1%lidocaine.

Using a number 11 blade, cut the skin above and perpendicular to the vein and cannulate with a 14 gauge angio catheter. Once the angio catheter is in place, remove the needle, pass the guide wire, followed by removing the catheter. Then, place the 11 french sheath and remove the guide wire before securing the sheath.

Ensure the patency and proper placement of the cannula by withdrawing dark red blood and performing a saline flush to confirm the flow and absence of swelling at the insertion site. After inducing propofol intravenously, intubate with an endotracheal tube using a laryngoscope with a number five blade as described in the manuscript. Confirm proper placement by the bilateral breath sounds and condensation on the endotracheal tube.

After preparing the operative field, shave the left anterior thorax. Then, apply sterile drapes around the disinfected surgical area. Make a 10 centimeter long skin and subcutaneous incision at the level of the fourth intercostal space.

Confirm the correct intercostal space is incised by identifying the thoracic inlet and counting the intercostal spaces downward. Subsequently, continue the incision in the center and along the fourth intercostal space. Now, divide the intercostal muscles, open the chest cavity and spread the ribs with a mini thoracotomy finochietto style retractor.

Avoid injuring the left internal mammary artery at the sternal border of the incision and the lung at the superior border. Then, perform baseline epicardial echocardiography to assess the biventricular function and valvular competence. Identify the left internal mammary artery at the sternal border of the incision, remove the adjacent tissues around it, and prepare to establish an arterial line for pressure monitoring.

Now, place two 4-0 silk sutures around the artery with one proximal and one distal to the cannulation site. Use titanium clips with a clip applier to clip the left internal mammary artery distal to the planned cannulation site to prevent backflow bleeding during cannulation. Make a perpendicular incision that is half of the circumference of the catheter in the left internal mammary artery with a number 11 blade.

Insert an 18 gauge angio catheter and attach it to the arterial line module. When proper placement of the angio catheter is confirmed by arterial pressure line reading, secure the catheter using two 4-0 silk sutures placed earlier. Next, perform pericardiotomy starting at the level of pulmonary artery sinuses and going four to five centimeters laterally along the main pulmonary artery taking care not to injure the left phrenic nerve.

Apply four to five retraction stitches to the opened pericardium to create a pericardial well which facilitates exposure and dissection between the pulmonary trunk and aorta. Using blunt right angle forceps, dissect the main pulmonary artery from ascending aorta around two to three centimeters from its origin as described in the manuscript. To separate the main pulmonary artery from the ascending aorta, use electrocautery or scissors to remove the connective tissue between the two structures.

Pass an umbilical tape around the main pulmonary artery with a blunt right angle clamp. Then establish a main pulmonary artery pressure line by placing a 5-0 monofilament purse string suture one centimeter distal from the main pulmonary artery sinuses. Insert a 20 gauge angio catheter and connect it to a monitoring line.

Before cinching the umbilical tape, ensure correct main pulmonary artery and arterial line readings are achieved. After holding both ends of the umbilical tape, clip them together to reduce the lumen of the main pulmonary artery. Then, tighten the band with the successive application of a clip applier as described in the manuscript.

Perform post banding echocardiography to assess the biventricular function and valvular competence as demonstrated earlier. Remove the main pulmonary artery pressure line. When maximal cinching and stable hemodynamic conditions are achieved, secure the umbilical tape to the adventitia of the main pulmonary artery using a 5-0 monofilament suture to avoid distal migration.

Then, remove the arterial line and ensure good hemostasis by checking for any bleeding from the area where the band and arterial lines were placed. Place a chest tube in the left thorax with the entry site one intercostal space below the initial incision. Close the ribs with two vicryl 2-0 sutures and close the wound with three layer continuous sutures.

Vicryl 2-0 for the muscle and subcutaneous tissues and proline 3-0 for the skin. Once good hemostasis is confirmed, remove the chest tube and extubate the animal. After the follow-up period, the mean TR grade increased from 0.4 to 3.2, demonstrating signs of evolving right ventricular failure and the development of significant TR after eight weeks of pulmonary banding.

Consistent with the echocardiographic examination. Over or under tightening of the band may result in the early animal demise or not inducing redicular failure and functional tricuspid regurgitation. Additional methods inducing heart failure may be performed after initial made pulmonary artery banding, like ventricle art pacing or ascending aorta banding, or band may be released to elevate right heart failure.