How I Do It: Pediatric Orthotopic Heart Transplant

In this video, the patient is a six-month-old, 6.4 kg infant with a new diagnosis of dilated cardiomyopathy. The patient was at home and presented at the hospital in extremis. The patient had increased work of breathing, distressed respirations, and poor distal perfusion (capillary refill > 4s). The patient was initially stabilized with epinephrine, milrinone, and calcium chloride drips once access was established. 

A transthoracic echocardiogram was obtained, demonstrating a severely dilated left ventricle, moderate mitral valve regurgitation, and severe left ventricular dysfunction with an ejection fraction of 12 percent. The patient was admitted to the cardiac intensive care unit for further workup. The patient was formally evaluated by the heart failure team and was ultimately listed status 1B for ABO-incompatible heart transplantation. After an approximately sixty-day wait, an acceptable donor became available. The recipient was brought to the operating room while the team awaited final acceptance from the donor team.

The donor’s stability was assessed by reviewing hemodynamics, recent arterial blood gas, and whether the patient required vasopressor/inotropic support. It was important to confirm that the anesthesia team had access to necessary medications and fluid should the donor become unstable prior to cross-clamp. Once a timeout and moment of silence were completed, a sternolaparotomy incision was completed in conjunction with the abdominal procurement team(s). The donor’s sternum was divided and the thymus/remnant was totally excised. The pericardium was divided along the midline and extended to an inverted T-shape along the diaphragm. The pericardium was then suspended with silk sutures, creating a pericardial well. If the lungs are also being procured, then the sutures are all placed on one clamp. If the lungs are not being procured, then the silk sutures are tied to the retractor. 

The heart was then thoroughly inspected. The heart was visually inspected for any signs of trauma, depending on the donor’s mechanism of death. The coronary arteries were palpated throughout. As nearly no donors under forty years old have angiograms completed, it is important to thoroughly assess the coronaries. The volume status of the heart was also inspected. The contraction and general kinetics of the ventricles were assessed. Any obvious dyskinesia was immediately reported. The heart was lifted out of the chest and the kinesis of the ventricles was assessed looking cephalad from the apex. If the heart is acceptable, a phone call is made to the recipient institution confirming this.

As much dissection as possible was completed as expeditiously as possible. Circumferential dissection of the superior vena cava and innominate vein was completed. The entire innominate vein was taken as a standard, as most recipients require this additional length. The azygous vein was isolated, doubly ligated in continuity with 2-0 silk ties and divided. The aorta was separated from the main pulmonary artery. If the lungs are not being procured, the branch pulmonary arteries are mobilized to the first order branches. The ascending aorta, aortic arch, innominate artery, left common carotid artery, and left subclavian artery were all circumferentially dissected. This dissection helped with an expeditious explant of the heart and reduced the amount of redundant tissue brought back, which can add to the cold ischemic time when the graft is being prepared for implant. The inferior vena cava was then circumferentially mobilized from the pericardial reflection. 

There is a good deal of variation in timing if the patient is a multiple-time redo sternotomy or if a ventricular-assist device is present. In this case, as much dissection as possible prior to the initiation of cardiopulmonary bypass was completed. This dissection can lead to delays for the donor team depending on complexity of the redo sternotomy and the travel time back to the recipient institution. Constant communication between the donor and recipient teams is paramount in these situations. In extreme cases of complex redo sternotomies, presence of ventricular assist devices, or prohibitively long travel times, the TransMedics OCS is used for warm preservation of the graft. This is exceptionally helpful to avoid excessively long cold ischemia times.

Following confirmation from the donor hospital that the graft was acceptable, the recipient was intubated and access was established. Depending on the distance from the donor institution, a median sternotomy was performed. Minimal dissection took place until the donor team was nearly ready to cross-clamp and explant the donor graft. A partial or total thymectomy was completed. The pericardium was divided along the midline and suspended, creating a pericardial well. Circumferential control of the superior vena cava (SVC), inferior vena cava (IVC), branch pulmonary arteries, and aorta were established. Purse string sutures were placed in the aorta near the base of the innominate artery, SVC, and IVC.

The donor team called and communicated with the recipient team when they were approximately five minutes away from being able to cross-clamp the aorta. If the recipient team and other donor procurement teams are agreeable to this timeline, then heparin is administered (300-400U/kg). After a waiting period of three minutes, a purse string suture was placed in the ascending aorta. The ascending aorta was cannulated, connected to the line with the preservation solution (UW Solution, 30-40 cc/kg), and clamped.

Once all procurement teams were ready to proceed, a large incision was made in the inferior vena cava. If the lungs are being procured, then a previously placed Satinsky clamp is released from the amputated left atrial appendage. If the lungs are not being procured, then a right-sided pulmonary vein is transected. The aorta was then cross-clamped and the preservation solution was  administered at around 80 mmHg. If the donor is under 20kg, the team will routinely deliver the preservation solution by hand via pre-filled 60cc syringes. This allows for better control of the pressure and minimizes the chances of distension should the left-sided vent become occluded. Ice was then placed in the mediastinum while the preservation solution was administered. 

Constant assessment of the aortic root and the left ventricle for distension is paramount during this time period. This is even more important if lungs are being procured because the volume of return of preservation solution from both the heart and lungs can lead to rapid distension if the left-sided vent becomes occluded. In an emergency, the aortic cross-clamp can be briefly released should distension become a problem without an immediate cause. After the heart preservation solution flush was completed, the cannula was removed and the purse-string suture was tied. The inferior vena cava was then transected with the help of the abdominal procurement team. This plane was followed underneath the heart, taking care to avoid injury to the coronary sinus. If the lungs are being procured, then an adequate pulmonary vein cuff and main pulmonary artery are negotiated between the procurement teams. If the lungs are not being procured, then the pulmonary veins are transected, followed by the superior vena cava and distal innominate vein. The branch pulmonary arteries were transected at their first order of branching. The brachiocephalic arteries were then transected. The aortic arch was transected distal to the left subclavian artery. Excess tissue was dissected away avoiding injury to the trachea and bronchi.

The heart was then removed from the chest and placed into a small basin with iced slush. The heart was then examined on the back table. The pulmonary veins were opened, creating a left atrial cuff. The atrial septum was also inspected. If a patent foramen ovale is found, it is closed with a continuous suture of 5-0 or 6-0 Prolene via the left atrium or via the inferior vena cava orifice. The cephalad surface of the branch pulmonary arteries was opened. None of the cuffs created were trimmed, that was left to the recipient surgeon to determine prior to implant. The heart was then placed in the appropriate container. Typically, the heart is suspended in the Paragonix SherpaPak for transport. The coordinators will communicate with the recipient team that the donor team is en route to the airport. Once the donor team arrived in the recipient’s city and was en route to the hospital, the recipient was cannulated onto cardiopulmonary bypass and the cardiectomy was performed.

Timing of placement onto cardiopulmonary bypass and cardiectomy is highly variable based on the recipients’ anatomy, complexity of the sternotomy, and pre-implantation work that needs to be completed (ie. ventricular assist device explant, branch pulmonary artery augmentation, aortic arch reconstruction). In this case, the cardiectomy was performed and an aortic cross-clamp was placed. No cardioplegia was necessary. Snares were lowered on the SVC and IVC. The IVC was transected at the IVC/RA junction. The SVC is transected at the SVC/RA junction. Transection at the junctions ensure adequate length and size of cuff for donor anastomosis. The pulmonary vein cuff was then created. The incision was made parallel to Sondergaard’s roove, ensuring an adequate cuff for donor anastomosis. The incision continued circumferentially between the left atrial appendage orifice and mitral valve. The left atrial appendage was subsequently amputated. The aorta was transected cephalad to the sinotubular junction, and the main pulmonary artery was transected cephalad to the pulmonary valve commissures. The heart was then removed from the chest.

The donor graft was brought onto the field. The left atrial cuff was trimmed to size and the aorta was transected at the level of the innominate artery. The heart was wrapped in an ice-soaked laparotomy pad and placed on the right edge of the sternal retractor. The anastomoses order was as follows:

1. Left atrium (LA)
2. Inferior vena cava (IVC)
3. Main pulmonary artery (MPA)
4. Aorta (Ao)
5. Superior vena cava (SVC)

Stay sutures were then placed in the donor left atrial cuff near the base of the SVC and near the IVC orifice. The sutures were then placed through the corresponding areas on the recipient to ensure that any potential size mismatch was accounted for and avoid twisting of the graft as it is lowered into the mediastinum. A double-armed suture (Prolene with a large needle) was passed through the cuff at the base of the left atrial appendage on the donor heart. The suture was then passed through the recipient pulmonary vein cuff cephalad to the left superior pulmonary vein orifice. After a few stitches were laid running caudally toward the IVC orifice, the donor heart was lowered into the chest. The suture was run continuously toward IVC orifice and terminated on the lateral edge of the IVC orifice. The opposite arm of the suture was then run continuously along the dome of the left atrium toward the IVC orifice and tied to the other end of the suture.

Marking sutures were then placed in the recipient IVC orifice at six and twelve o’clock. A double-armed Prolene suture was passed through the recipient IVC cuff. The suture was passed through the donor IVC cuff and run continuously along the posterior edge. The opposite arm of the suture was run along the anterior edge. If there is a significant size mismatch present, then a small incision can be made cephalad on the donor IVC to correct.

The donor MPA was then trimmed to size. It is important to avoid any excessive length in the PA to avoid kinking at the level of anastomosis. Double-armed Prolene sutures were passed through the medial and lateral edges of the recipient branch PAs. The opposite arm of the lateral suture was passed through the corresponding lateral edge of the donor PA. The posterior edge of the anastomosis was completed. The other arm of the lateral suture was then run continuously along the anterior surface, completing the anastomosis.

The donor aorta was then trimmed to size. It was important to avoid any excessive length in the aorta to avoid kinking at the level of the anastomosis. A double-armed Prolene suture was passed through the lateral edge of the recipient ascending aorta. The opposite arm of the lateral suture was passed through the corresponding lateral edge of the donor ascending aorta. The posterior edge of the anastomosis was then completed. The other arm of the lateral suture was then run continuously along the anterior surface, completing the anastomosis. A buttress layer of bovine pericardium or Teflon felt strip can be used to ensure adequate hemostasis of the posterior suture line. An active root vent was placed in the ascending aorta. Deairing maneuvers were performed and the aortic cross-clamp was removed.

Correct orientation of the donor SVC is paramount prior to anastomosis. The ligature that is left on the proximal azygous vein aids in keeping the orientation correct. Typically, if the heart is beating, a small titanium clamp is placed on the donor SVC to avoid blood obscuring the surgical field. In this case, double-armed Prolene sutures were passed through the medial and lateral edges of the recipient SVC. The opposite arm of the lateral suture was then passed through the corresponding lateral edge of the donor SVC. The posterior edge of the anastomosis was then completed. The other arm of the lateral suture was then run continuously along the anterior surface, completing the anastomosis. It is important to avoid the purse-string effect on this anastomosis. There are several ways to avoid this:

1. Lock every third bite on the continuous suture line along the posterior edge.
2. Run the posterior suture line continuously and interrupt the anterior suture line.
3. Run the entire posterior and anterior suture lines continuously and tie with an intentional air knot, allowing the SVC to expand once it is filled.

Once the anastomoses were completed, the heart was allowed to reperfuse under warm conditions while being supported on cardiopulmonary bypass for approximately 10 minutes for every hour of cold ischemic time. The patient was then weaned and separated from cardiopulmonary bypass and modified ultrafiltration was completed. The patient was then decannulated. Any surgical bleeding was addressed and hemostasis was achieved. The sternum was reapproximated and the presternal tissues were closed in layers. Once hemodynamics were acceptable, the patient was transferred to the cardiac intensive care unit for handoff.

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