TSRA Content:
Authors: Lin Chen, BA, Mona Kakavand, MD, Rachel Nemoyer, MD
Donor Selection:
Heart transplantation begins with donor selection. Trainees should familiarize themselves with the quality and functional assessment of the donor heart. Major components include donor history, hemodynamic evaluation, and laboratory and imaging findings.
- Age – the upper limit of acceptable organs has gradually increased over the past several decades. Most centers use donor age <55 years old as a component in the selection criteria, although some centers use donor aged 65 years old and greater.
- History of chest trauma or cardiac insult – many potential donor hearts may have undergone thoracic trauma and/or cardiopulmonary resuscitation. Modest elevation in cardiac troponin I levels may be expected and should be considered the in context of patient history and time between inciting event and laboratory results.
- Echocardiographic evaluation – findings must be carefully examined for donor-recipient size match, ventricular function, appropriate hemodynamics (mean arterial pressure > 60 mmHg and central venous pressure 8-12 mmHg), and any potential structural abnormalities such as valvular dysfunction and/or left ventricular hypertrophy, that may confer poor long-term function and survival. Inotropic or vasopressor support are common, but donor hearts requiring significant support (ex. >10 mg/kg/min of dopamine or dobutamine) may be a contraindication to donation. Coronary angiography should be considered for older donors or those with a history or risk factors for coronary artery disease including hypertension, diabetes mellitus, hyperlipidemia, family history, or concerning findings on echocardiogram.
Procurement:
Review
Prior to making any surgical incision, the surgeon should confirm and review the consent for organ donation, ABO blood group, brain death note(s), chest x-ray, echo, and cardiac catheterization. Several factors may impair the surgeon's ability to accurately assess the donor's heart including the use of inotropes or the administration of beta blockade prior to arrival in the OR and should be conveyed to the attending surgeon.
Preparation
Standard preparation includes positioning supine with the placement of a shoulder roll, both arms tucked, and a surgical prep from chin to knees. A sternotomy is made from sternal notch to xiphoid, the pericardium incised, and pericardial stay sutures placed. As part of the cardiac assessment, one should palpate the coronary arteries to feel for calcifications, visualize the right ventricle, and lift up the apex of the heart to assess the left ventricle. One is looking for what is often termed a "snappy heart," which means a heart with good contractility and rapid rebound. The heart should have a twisting/torsion motion at the apex. Finally, all visible segments of the heart should be inspected for wall motion abnormalities. The size of the heart should be assessed to determine if it is an appropriate match for the recipient.
A minimalist approach to dissection will decrease the chance of injury to the vessels and will shorten the time to cross-clamp. A thorough dissection however will hasten the explant as well as lower the risk of injury during the explant as the vessels are harder to delineate when they are no longer blood-filled. Both dissection and explant are facilitated by adequate exposure.
Dissection
Using sharp dissection or electrocautery, make a window between the aorta and pulmonary artery. Err on the side of the aorta to avoid injury to the pulmonary artery. Have the assistant retract the aorta while the surgeon completes the window by dissecting the posterior aspect of the aorta off the right pulmonary artery. Umbilical tape may be looped around the aorta and later used for retraction.
Next, free the superior vena cava (SVC) from the right pulmonary artery (RPA). Incise the pericardium just cranial to the RPA and medial to the SVC. Open up the plane between the SVC and RPA with a Metzenbaum scissor or right angle. The SVC should be freed circumferentially at the level of the RPA, and this may be extended cranially to the azygous vein. Care should be taken to avoid stimulating the phrenic nerve. The azygous vein should be identified, encircled with a 2-0 silk and tied down. Next encircle the SVC with a vessel loop or umbilical tape cranial to the azygous. This will be snared prior to placement of the cross-clamp. If there is a lung team, the bifurcation of the pulmonary artery (PA) should be dissected out and the heart and lung team should agree on a cannulation site.
Prior to heparinization, it is important to communicate with the recipient team to ensure the donor heart will arrive “on time” to minimize cardiac ischemic time. Place a U-stitch or a purse string suture in the ascending aorta using a 4-0 prolene. Three minutes after heparin administration, a Bentley needle is inserted, snared down, and connected to the cardioplegia tubing, which has already been deaired.
Preparing to Vent the Heart
Before cross-clamping, confirm the location at which the inferior vena cava (IVC) will be incised with the liver team. If there is no lung team, prepare to vent via the left inferior pulmonary vein. If there is a lung team, we prefer to place a Satinsky clamp on the left atrial appendage before excising the appendage distal to the clamp. Later, this clamp is removed in a controlled manner while cross-clamped to vent the left ventricle. When all teams have vocalized, they are ready for cross-clamp, proceed in the following manner.
The Harvest
If there is no lung team, open the pericardium (like you would do for a mammary artery harvest) so that warm blood is allowed to pool in the pleural space during cross-clamp. Confirm that the azygous vein has been tied down and snare the SVC. If there is no lung team, vent the left inferior pulmonary vein. Next, vent the NC. Note that if the NC is vented first, blood pools in a dependent fashion making it difficult to see the left inferior pulmonary vein. If there is a lung team, vent the IVC before releasing the Satinsky clamp from the left atrial appendage. Alternatively, the assistant may elevate the left atrial appendage as the surgeon amputates the distal end. Position pool suckers adjacent to the two vents to suction the warm blood and preservation solutions. Place ice slush on the heart and watch as the heart beats and empties out the blood. This takes approximately 10 seconds from the time it was vented. We prefer to cross-clamp the aorta after the heart is decompressed to prevent a full left ventricle from beating against a clamped aorta.
Cross-clamp the aorta and perfuse the heart with cardioplegia. The arrest should be immediate, and the coronaries should blanch. If the heart does not arrest immediately, the surgeon should begin to trouble shoot. (Is the aortic catheter dislodged? Is the cardioplegia tubing clamped by the surgeon or the perfusionist? Is the cross-clamp appropriately positioned)? Palpate the aortic root pressure and confirm that it is not too low. This will need to be verified for the duration of the cardioplegia infusion. Palpate the left ventricle for distension. This is particularly important when a lung team is infusing pulmoplegia. If ventricular distension occurs, release the cross-clamp, check the adequacy of the left atrial vent, check the suction, and allow the heart to decompress before resuming the cardioplegia infusion.
Once satisfied with the arrest and perfusion, the surgeon can begin the cardiectomy. With small cuts begin to transect the IVC. Care should be taken not to cut too caudal thus giving the liver team an inadequate length of IVC or too cranial as one may injure the coronary sinus. Next, transect the SVC cranial to the azygous. Transect the azygous. Incise the aorta to allow for the release of any blood before removing the cross-clamp and transecting the aorta just proximal to the brachiocephalic trunk.
If there is a lung team, remove the pulmonary artery cannula. With small bites open the cannula site, visualize the orifice of the right and left pulmonary veins, and transect the pulmonary artery at the level of the bifurcation. If there is no lung team, cut the right and left pulmonary arteries and take the bifurcation. Gently lift the heart and take care to ensure the SVC is in one's hand. If there is no lung team, transect each of the four pulmonary veins. If there is a lung team, make a stab incision in the center of the left atrium with an 11-blade scalpel. With the help of the assistant grasping and elevating the left atrial appendage, look inside the left atrium and visualize the orifice of the left superior and inferior pulmonary veins. Cut in a caudal-cranial direction towards the left atrial appendage and leave a 1 cm rim of tissue around the pulmonary veins.
After rounding the left superior pulmonary vein, flatten the Metzenbaum scissors and begin to cut towards the surgeon's side (patient's right) and stop upon reaching the halfway point. Next, begin where the left atrium was initially incised with an 11-blade. Make small cuts in the atrium towards the right inferior pulmonary vein taking care to look inside the atrium and visualize the orifice of the right superior and inferior pulmonary veins. This angle is hard to see from the surgeon's side. Cut in a caudal-cranial direction and leave a 1 cm rim of tissue around the pulmonary veins. After rounding the right superior pulmonary vein, flatten out the scissors, and continue to cut across the left atrium until one meets the halfway point.
If the SVC is not securely positioned in the surgeon's hand, it may be injured during the excision of the left atrial cuff. Finally, free the remaining tissue between the heart and the posterior aspect of the pericardial sac. The heart should be placed in a basin filled with cardioplegia solution and examined for any injury. Package the heart in 3 sterile bags, with the first bag containing 1 L of cardioplegia solution preferred by one's institution and subsequent bags with 1 L of cold saline. Take care to remove as much air as possible in the bags before positioning the heart in the cooler and covering it with ice.