Heart Transplantation




Abstract


As we celebrate the 50th anniversary of the first human heart transplant in December 1967, we marvel at the tremendous medical advances that have taken place. Surprisingly few modifications have occurred since the original surgical technique was described by Shumway and Lower. The following chapter describes the surgical conduct of both the donor procurement and recipient implant for modern cardiac transplantation.




Keywords

heart transplant, surgical technique, donor management

 




Donor



Surgical Anatomy and Exposure





  • The potential donor is placed supine on the operating room table. The standard incision for the multiorgan donor is a midline sternotomy incision extended into a midline abdominal incision to expose the liver, kidneys, small bowel, and pancreas ( Fig. 33.1 ).




    Figure 33.1


    Midline incision (dotted line) to expose the organs to be retrieved.



  • The superior vena cava (SVC) lies partly outside the pericardium. It is anterior and to the right of the trachea and its surrounding nodal tissue. The arch of the azygos vein is noted posteriorly as the only branch of the SVC. This is an important landmark because the SVC should be harvested beyond the insertion of the azygos vein and, if possible, to the origin of the innominate vein.



  • Nine vessels are exposed during retrieval—the two cavae, four pulmonary veins, the aorta, and the right and left pulmonary arteries. If the heart is retrieved as the sole thoracic organ, the pulmonary veins are divided, and the pulmonary artery is divided at the level of the bifurcation. The inferior vena cava (IVC) is usually left with the hepatic resection because the inferior anastomosis is donor right atrium to recipient IVC.



  • If the lungs are being simultaneously harvested with the heart, the transverse pericardial sinus is explored in situ. The lung team usually cannulates the distal pulmonary artery at the level of the bifurcation to facilitate organ flushing and the administration of preservative solution. The left atrium is divided halfway between the coronary sinus and the insertion of the pulmonary veins.




Preoperative Considerations



Selection and Management





  • Risk matching between donor characteristics and recipient needs ensures maximal utilization of the potential donor pool and minimizes the risks associated with longer waiting lists. For example, a heart from a higher risk donor may be used in an older recipient with previous surgery, but not in a younger recipient who is a good candidate for an assist device. The typical risk factors for donor hearts include advanced age, prolonged ischemic time, preexisting ventricular dysfunction and/or coronary disease, and the need for inotropic support. Furthermore, it is unwise to compound risk (e.g., use an older donor subjected to a prolonged ischemic time).



  • Common causes of brain death include trauma and intracranial bleeding. Suicide remains a common cause, with the mode of death incorporating both anoxic and traumatic brain injuries. Opioid intoxication is an increasingly frequent cause of donor death. Cardiac donations after circulatory arrest have been recently reported and are likely to increase in the future.



  • Screening for a given recipient begins with confirming blood type compatibility and the approximate size, height, and weight for the patient, as well as gender. Ensuring an appropriate-sized donor (> 0.8 of the recipient’s size) remains a key component in the selection of donor-recipient matches. The size match guideline may be adjusted if the donor is female and the recipient is male (closer height to weight match). It may be widened if the donor is a younger male or if there is a shorter anticipated ischemia time. Recipient pulmonary vascular resistance (PVR) must also be taken into account, and a larger older donor is usually preferred. Some surgeons contend that an 80-kg male donor is adequate for any size of recipient.



  • The female donor older than 35 years with an intracranial bleed must be evaluated carefully. This cause of death is frequently associated with hypertensive disease and left ventricular hypertrophy (LVH). LVH as assessed by echocardiographic measurement of septal and posterior wall thickness and electrocardiographic criteria should be judged in the context of the patient’s body surface area. The use of hypertrophied hearts can significantly affect graft survival, particularly in the presence of electrocardiographic criteria that reflect a long-standing history. However, LVH can be overestimated in donors who are hypovolemic.



  • The ideal donor should have excellent cardiac function with appropriate filling pressure and normal anatomy. He or she should not require any inotropic support; however, pressor support to overcome low systemic vascular resistance is usually acceptable. Many centers will accept a heart with a low filling pressure (<10 mm Hg) and no inotropic support, even in the absence of echocardiographic assessment.



  • As donor age increases, the depth of evaluation increases as well. Cardiac catheterization is recommended in all males older than 45 or females older than 50 years. Donors with known risk factors for coronary disease should also undergo angiography. These risk factors include diabetes, hypertension, hyperlipidemia, smoking history, and a history of cocaine abuse.



  • The presence of any coronary artery disease is usually a contraindication to utilization for a standard donor. However, in extenuating circumstances for a recipient at high risk for imminent death, simultaneous coronary bypass surgery can be performed.



  • Hepatitis C has traditionally been a contraindication to heart donation because it may predispose the recipient to liver dysfunction and coronary graft disease. However, newer antivirals are now permitting the successful use of hepatitis C positive donors. Similarly, hepatitis B core antibody immunoglobulin G (IgG)–positive donors may be used for high-status recipients if immunoglobulin M (IgM) is negative. In such cases, the risk of transmission is considered low (< 5%–10%).




Donor Management





  • The ideal management of the multiorgan donor has been previously published. β-Adrenergic inotropic support should be avoided if possible. Hormone replacement with thyroxine (T 4 ) infusion, vasopressin, and methylprednisolone should be administered routinely, regardless of baseline LV function. Systemic blood pressure should be titrated to less than 120 mm Hg after appropriate volume resuscitation. Anemia should be corrected because this will cause hypotension. A P co 2 of 30 to 35 mm Hg should be sought to decrease PVR. In the common presentation of systemic hypertension, therapy should consist of sodium nitroprusside or short-acting beta blockers such as esmolol.



  • The retrieval team should strive to keep the donor heart relaxed and undistended. Intraoperative management of the donor includes inhaled anesthetic agents for blood pressure control and judicious volume resuscitation to maintain a central venous pressure (CVP) of 8 to 12 mm Hg. Right ventricular (RV) distention or stress is often noted when the systemic blood pressure rises above 110 to 120 mm Hg.




Operative Steps



Visualization





  • On arrival, the retrieval team checks donor blood type against that of the recipient, as well as donor consent, certification of brain death, and other pertinent data.



  • Communication between the donor and recipient surgical teams is essential. A nonscrubbed assistant is preferred who can keep the recipient team apprised as to expected cross-clamp and travel times.



  • A generous median sternotomy is performed and extended into a midline abdominal incision. A short retractor is placed, with the cross bar at the superior aspect of the incision so as not to disturb exposure for the liver transplantation team.



  • A pericardial cradle is created with stay sutures. The lung transplantation team may choose to secure these with clamps so that access to the pleural spaces is maintained.



  • The heart is visualized and inspected for adequate function. The right ventricle is readily visible. One should note a relaxed right atrium, as well as a relaxed outflow tract. The heart should be displaced gently to assess left ventricular (LV) function and to look for a left SVC. When examining the posterolateral wall, hypotension commonly occurs. The rate of return to normal hemodynamics is a good indicator of myocardial function.



  • In older donors, the coronary arteries should be palpated. Usually, a cardiac catheterization study will have been done. Diffuse coronary artery disease may not be obstructive but would still preclude donation. Extensive calcifications, although not necessarily stenotic, also preclude use of the organ. The donor heart is examined for signs of long-standing hypertension such as increased epicardial fat, tortuous coronary arteries, and a shortened ascending aorta with effacement of the sinotubular junction.



  • An estimate of heparin and clamp time is determined with the other organ retrieval teams. The timing of recipient and donor operations is individualized secondary to reoperative status, ventricular assist device (VAD) excision, and anticipated travel times. My team usually allocates 2 hours for sternal reentry and explantation of an implantable VAD. I would time the donor cross-clamp so that arrival of the allograft in the recipient operating room would coincide with the initiation of cardiopulmonary bypass. In cases for which total ischemic time is expected to be prolonged, cardiopulmonary bypass is often initiated 10 to 20 minutes prior to anticipated allograft arrival to allow for recipient cardiectomy.



  • The aorta and pulmonary artery are separated to allow for aortic cross-clamping without interfering with pulmonary artery cannulation by the lung team. The SVC is mobilized from the right pulmonary artery. I usually isolate the SVC with a silk tie, which is subsequently tied after the aortic cross-clamp is applied.



  • A back table setup is prepared and checked at this time to allow efficient preparation and packaging. The packing plastic bag is prepared in a large basin filled with iced saline slurry. The bag is filled with 1 L of the same solution that is used for flush cooling. This setup keeps the storage solution cold and prevents ice from coming into direct contact with the heart. An aortic cross-clamp is also selected.




Organ Recovery





  • Preparation is made to allow adequate suction and venting into the right chest. The pericardium adjacent to the IVC is divided to allow drainage into the right chest. This drainage can be collected with a pool suction. Another pool suction is prepared for insertion into the IVC, which will be incised.



  • The cardioplegia bag should be kept in a cooler until just before heparin is given. An assistant or preservationist hangs and administers the cardioplegia. Heparin (300 U/kg) is administered intravenously. A cardioplegia cannula is inserted into the ascending aorta, just distal to the fat pad. After securing the cardioplegia cannula, the tubing is passed off to be connected to the preservative solution bag. The line is de-aired, clamped, and connected. Cardioplegic administration can be performed with either a pressure monitoring line or a pressurized infuser. Care should be taken to avoid pressures higher than 200 mm Hg. Measuring cardioplegia pressure is particularly important for pediatric and adolescent donors in whom the aorta is small, and pressure estimation by palpation is unreliable. Flush cooling at supraphysiologic pressures may cause edema of the donor organ, potentially leading to dysfunction.



  • The flush cooling sequence is initiated by the cardiac team in coordination with the abdominal team. The aortic clamp is applied and cardioplegic solution administered. The SVC is ligated and the IVC is hemisected anteriorly to vent the right heart. The left heart is similarly vented by an incision into the left atrial appendage. A suction catheter is placed inside the IVC and in the right pleural space ( Fig. 33.2 ).




    Figure 33.2


    Venting of the left and right heart immediately after aortic cross-clamping.



  • I usually infuse 3 L of cold Celsior solution (Genzyme, Cambridge, MA) and then store the explanted heart in 500 mL of cold Celsior solution. I avoid topical ice because it can lead to crystallization of epicardial fat and occasional hemorrhage of epicardial microvessels. The heart is usually cooled to a temperature of 4° to 10°C (39.2°–50°F).



  • It usually takes 6 to 8 minutes to flush-cool the heart. During this time, blood is observed clearing from the coronary arteries, and the surgeon ensures that there is no right or LV distention.



  • Once the cardioplegia is given, the aorta should be transected if pneumoplegia is still being given, as is usually the case. This should help further to vent the left-sided cardiac chambers and to prevent the pneumoplegia from washing out the cardioplegia.



  • The IVC is then divided. I usually have the abdominal team provide caudal traction to the liver. As described previously, most of the suprahepatic IVC is kept with the liver resection. The heart is elevated and retracted to the left to expose the right pulmonary veins for division at the pericardial reflection. The heart is then retracted superiorly and to the right to expose the left pulmonary veins. As described previously, if the heart is the sole thoracic organ being procured, the pulmonary veins are divided at the pericardial reflection. If the lungs are also being harvested, a left atrial incision is made between the coronary sinus and the insertion of the pulmonary veins ( Fig. 33.3 ).




    Figure 33.3


    Incision lines for combined heart and lung retrieval.



  • The main pulmonary artery is divided proximal to the pneumoplegia cannula site at the bifurcation. Again, the surgeon should look inside to follow the contour of the bifurcation and protect the pulmonary valve. I prefer to separate the heart from the lung block in situ (vs. on the back table).



  • Downward traction is applied to the aorta, and it is divided beyond the clamp site. The azygos vein is divided, as is the SVC above the site of ligation. The heart is then delivered to the back table and placed in the cold preservation solution.




Postretrieval Care





  • Donor pericardium and paratracheal lymph nodes are harvested at this point, if this was not done previously. The pericardium is packaged with the donor heart. If needed, this can be used for patches or pledgets during the recipient operation. In congenital cases, this pericardium is also useful for augmentation of native, recipient pulmonary arteries or other great vessels.



  • A rapid assessment is performed to assess surgical damage, valve competency, and the presence of a patent foramen ovale, which should be closed. I inspect the ostia of the coronary arteries to rule out undetected disease or abnormal takeoffs, which may predispose to sudden cardiac death. Finally, the junction of the IVC and right atrium are inspected to ensure that an adequate rim of atrial tissue is present next to the coronary sinus.



  • The remaining back table dissection may be performed before packaging. This dissection includes preparing the left atrial cuff for anastomosis by dividing the pulmonary veins from superior to inferior on either side and incising the posterior left atrium (in case of solitary heart retrieval). The mitral valve is inspected carefully. The pulmonary artery is splayed open and dissected away from the left atrium and SVC on the right. This will already have been done in situ when lung retrieval has been carried out.



  • The heart is placed in 500 mL of preservation solution inside a plastic jar. This jar is then placed into two separate sterile bags. The outer bag is subsequently contaminated during transport, allowing for subsequent retrieval of the inner sterile bag and jar. The jar and overlying bags are then placed in a cooler surrounded by ice.




Pearls and Pitfalls





  • Frequent communication is necessary with the recipient team to convey adjustments in time to optimize donor ischemic time. I instruct the donor team to notify us just prior to anticipated cross-clamping, on departure from the donor operating room, on flight departure and arrival (or estimated ground travel time) and, finally, when they are approximately 10 minutes away from the recipient operating room.



  • Donor blood pressure will rise with stimulation. Inhaled anesthetic agents should be used to keep systolic blood pressure at a maximum of 120 mm Hg. Transfusion of the donor with packed red blood cells should be encouraged to avoid anemia (hemoglobin < 8 g/dL).



  • Often, the initial donor incision is performed by the abdominal retrieval teams because they generally require 1.5 to 3 hours to prepare their organs for retrieval. Careful inspection for hemostasis—particularly thymic and phrenic vessels—can avoid anemia. In general, discourage the abdominal team from contaminating the thorax with intraabdominal contents (e.g., omentum, small bowel). Particularly in cases of trauma, these structures may no longer be sterile and could potentially lead to life-threatening infection in the cardiac allograft.



  • Focused communication with the lung harvest team is needed to avoid cardiac distention, which can be extremely deleterious to the posttransplantation function of the donor heart. It is important to wait until the left atrial appendage is vented and the heart is arrested before starting lung perfusion. This also prevents the lung perfusate from displacing the cardioplegia solution from the aortic root. If the cardioplegia has finished infusing before the pneumoplegia, the aorta must be transected and suction carefully advanced toward the aortic valve to prevent the pneumoplegia from washing out the cardioplegia. Pneumoplegia may be toxic to the heart and coronary arteries.



  • In severe chest or abdominal trauma, the surgeon must always be alert to the possibility of hematomas around the aorta or innominate vein, which may be a source of important blood loss on opening the chest.



  • Excessive manipulation of the donor heart during flush cooling may cause transient aortic valve incompetence, with ensuing right and LV distention, and therefore should be avoided.



  • On excision, it is crucial to avoid damage to the coronary sinus during division of the IVC and left atrium. Suboptimal length of the SVC can lead to sinoatrial node damage.


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Jan 26, 2019 | Posted by in CARDIAC SURGERY | Comments Off on Heart Transplantation
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