A High-Fidelity Porcine Model of Orthotopic Heart Transplantation Following Donation after Circulatory Death

We present a high fidelity porcine model of heart transplantation after circulatory death, enabling evaluation of DCD related pathophysiology and supporting translational research to improve allograft recovery. Since 2019, clinical adoption DCD heart transplantation has grown in the United States with recent trials showing non-inferior short-term survival when compared to concessional brain death donation methods. Outcomes after DCD heart transplantation have further been improved by advances in RAF free profusion methods, including direct procurement and normothermic ex vivo perfusion, as well as normothermic regional perfusion.

Primary graft dysfunction remains a key driver of short-term mortality after DCD heart transplantation. While warm ischemic injury and metabolic derangement are proposed contributing factors, the underlying mechanism behind PGD still remains unknown. This porcine model replicates clinical DCD procedures with adjustments for species-specific anatomy.

In addition, ex vivo perfusion supports the development of targeted therapies to enhance allograft preservation and function. After performing a carotid cutdown and exposing the donor heart, perform baseline analysis of the allograft, including pressure volume loop recordings. To begin, measure the length of the solid state pressure volume catheter from the cannulation site to the apex of the swine heart.

Introduce the catheter sequentially into the carotid artery and internal jugular vein. Guide the catheter to the left and right ventricles under epicardial ultrasound guidance. Prepare the donor heart for explant by cannulating the aortic root with a seven French vent, securing it with a room tourniquet and placing a purse string stitch in the right atrial appendage.

Cease mechanical ventilation to initiate the controlled circulatory death process. The heart may distend. Wait for 10 minutes after confirmed death defined by pulseless electrical activity and no signs of life before proceeding.

Slow pulseless electrical activity persists in swine longer than in humans, resulting in increased allograft ischemic insult. For ex vivo profusion device priming, use a number 11 blade to make a stab incision into the right atrial appendage and cannulate with the 34 French venous cannula. Secure the cannula with a rummel tourniquet and connect it to the ex vivo perfusion devices collection bag.

Collect approximately 1, 200 to 1, 500 milliliters of donor blood into the manufacturer provided collection bag. Following collection of the donor blood, apply the aortic cross clamp. Administer one liter of del Nido cardioplegia into the aortic root, targeting a pressure of 60 to 100 millimeters of mercury.

Transect the inferior vena cava and left atrial appendage to vent both ventricles during cardioplegia delivery. Divide the inferior vena cava, superior vena cava, aorta just distal to the innominate artery and pulmonary artery at the bifurcation. Then transect the donor left atrium, ensuring a sufficient cuff remains.

Remove the heart and place it in a basin filled with cold, sterile slush for back table preparation. Place four equidistant pledged horizontal mattress sutures using 4-0 Prolene suture inside the distal end of the aorta. Then insert the ex vivo profusion aortic adapter and secure with 0-0 silk suture or umbilical tape.

Transport the allograft to the ex vivo perfusion device and connect the adapter. Position the heart with the posterior side facing up and obtain perfuse 8 samples, blood work and biopsy samples during this stage. In this model, the allograft remained on the ex vivo perfusion device at 34 degrees Celsius for two to three hours before implantation into the recipient.

After exposing the recipient's native heart, prepare for cardiectomy. Cannulate the distal ascending aorta, and then perform by caval venous cannulation. Apply the aortic cross clamp proximal to the cannula and explant the recipient heart.

Leave intact atrial cuffs for biatrial implantation. Transect the aorta and pulmonary artery close to the root. Once the recipient's native heart has been explanted, begin by atrial implantation of the donor allograft and start the left atrial anastomosis using 4-0 Proline suture.

Then complete the pulmonary artery, aortic and right atrial anastomosis with continuous 4-0 Proline suture. After completing all anastomosis, release the aortic cross clamp to reperfuse the allograft. Ensure hemostasis of all anastomosis.

After 60 minutes of reperfusion, attempt to wean the recipient from cardiopulmonary bypass. The recipient animal was supported for one hour post-separation from cardiopulmonary bypass. In the DCD procurement phase, the elapsed time from cessation of life-sustaining measures in the donor pig to the declaration of death was approximately 14.25 minutes.

Operative cardiopulmonary bypass time in the recipient animals was around three hours with a cross clamp time of on average 1.5 hours. Post-transplant epicardial echocardiographic assessment was performed to evaluate graft function following implantation. Standard short axis, fourth chamber, and two chamber views were obtained.

Post-transplant graft function varied from mild graft dysfunction with stable hemodynamics to severe dysfunction with hemodynamic instability.