Many patients who survive into adulthood with congenital heart disease (CHD) will develop progressive cardiopulmonary dysfunction. Some will develop ventricular failure, some will have pulmonary hypertension, and many will experience progressive cyanosis. Among these patients, some will require cardiac replacement, others will need heart-lung transplantation, and a few may be suitable for lung transplantation with repair of the congenital defect. In many, the risks of transplantation may be prohibitive, and continued medical management will be the best option. Risk stratification for this challenging group of patients requires comprehensive evaluation by a multidisciplinary team that includes transplant surgeons as well as cardiologists with special interest and expertise in adult congenital heart disease (ACHD). Other specialists may be required to assess important comorbidities such as renal and hepatic dysfunction.
Indications
Little is known about the long-term needs for thoracic transplantation in ACHD. The 2015 report of the Registry of the International Society for Heart and Lung Transplantation (ISHLT) shows that only 3.3% of adult heart transplants were performed for a diagnosis of CHD in the current era (2009–2014) 1 ; a significant increase compared with 2% of adult heart transplants performed for this diagnosis in the era 1992–2003. Similarly, only a small proportion of adult lung transplantations (0.9%) are performed for this diagnosis. By contrast, CHD accounted for more than one-third of adult heart-lung transplants reported to the registry between 1982 and 2014. Indeed, CHD remains the most common diagnosis leading to heart-lung transplantation in children and adults. However, the total number of heart-lung transplants performed annually has fallen dramatically since its peak in the early 1990s ( Fig. 14.1 ), reflecting a better understanding of which patients can be managed with single and bilateral lung transplants and a desire to optimize use of scarce thoracic organs. This trend may disenfranchise patients with complex CHD that can only be managed by heart-lung transplantation. Listing criteria for adult patients with CHD warrants careful refinement.
The number of thoracic transplants performed for the indication of CHD almost certainly underestimates the true need. Many patients are not referred for consideration for transplantation because it is assumed that their disease may be too complex or the risk is too high. Others die while on the waiting list. With almost all forms of CHD now deemed suitable for palliation or repair in infancy and childhood, an ever-increasing population of patients with severe forms of CHD is now reaching adult life. Thus increasing demand for transplantation in adults with CHD is inevitable.
Types of Heart Disease Requiring Transplantation
A few patients who have never undergone palliation for their congenital defects survive into adult life. These include patients with simple anatomic defects such as atrial or ventricular septal defect or patent arterial duct who have developed pulmonary vascular disease. Few such patients without prior surgery will be suitable for isolated heart transplantation. Another population is composed of patients who were palliated for complex cyanotic heart disease (with reduced pulmonary blood flow) before the modern era of congenital heart surgery. Many of these underwent systemic-to-pulmonary shunts such as Waterston or Potts procedures or a classic Blalock-Taussig shunt. These (relatively) unrestricted shunts provided excellent long-term palliation for many patients but caused chronic ventricular volume overload as well as excessive pulmonary blood flow, resulting in ventricular dysfunction and pulmonary hypertension that is generally irreversible. Some of these patients are potential heart-lung transplant candidates.
An increasing population of patients referred for transplant consideration are those palliated with partial (Glenn) or complete (Fontan) atriopulmonary or cavopulmonary anastomoses. It is now recognized that the Fontan procedure is palliative, although complete, or near complete, separation of the circulations is achieved. Most patients with Fontan circulation will likely need consideration for heart transplantation at some point in their adult life. Of note, those receiving Fontan palliation for a diagnosis of hypoplastic left heart syndrome are much more likely to develop “Fontan failure” with potential need for transplantation.
Two final groups of patients form a significant proportion of adults with CHD who are referred for consideration for thoracic transplantation. These are patients with tetralogy of Fallot with complex pulmonary atresia and patients with simple transposition of the great vessels who underwent childhood repair with atrial baffling (Mustard or Senning procedure). The former group poses enormous challenges. Most are referred for consideration of heart-lung transplantation with progressive cyanosis. Some have never been palliated, but many have received one or multiple systemic-to-pulmonary shunts, often with multiple unifocalization procedures. Patients with right ventricular failure after a Senning or Mustard procedure are also being seen with greater frequency as it becomes apparent that the systemic right ventricle is unlikely to perform well into late adult life. Several years ago it was believed that many of these adults with right ventricular failure could be helped by left ventricular training and subsequent atrial baffle takedown and arterial switch procedure. It is now recognized that the mortality of this approach is very high in the older patient, and most of these patients are probably best considered for heart transplantation.
Timing of Transplantation
For patients with ischemic or dilated cardiomyopathy, a number of risk factors for survival have been recognized. Peak oxygen consumption has proved a useful guide for timing of transplantation. In the setting of CHD, no such guidelines exist and each patient’s pathophysiology is unique. Life expectancy of less than 2 years can be considered a good indication for listing, given the long waiting times for donor organs in this population. This is not always easy to predict and emphasizes the need for involvement of physicians highly experienced in the management of adults with CHD in the transplant evaluation. Evaluation of quality of life is as important as estimation of survival in determining the timing of transplantation. It must also be remembered that many adults with end-stage CHD may not be suitable for ventricular assist device support as a bridge to transplantation and, overall, mechanical circulatory support may not improve waitlist mortality in this population. Therefore late referral should be avoided.
Pretransplantation Evaluation
The principles of evaluation of the thoracic organ candidate are covered in detail in standard texts. Specific considerations in the evaluation of the patient with ACHD are summarized in Box 14.1 .
Anatomic
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Anomalies of cardiac situs
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Anomalies of systemic and pulmonary venous return
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Presence of pulmonary arterial hypoplasia, stenoses, and distortions
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Presence of discontinuous pulmonary arteries
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Presence of pulmonary arteriovenous malformations
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Presence of aortopulmonary collateral circulation
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Diaphragmatic function
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Number of prior sternotomies and thoracotomies
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History of pleurodesis or pleural/mediastinal sepsis
Physiologic
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Estimation of pulmonary vascular resistance
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Estimation of cardiac function and reserve (lung transplantation with cardiac repair)
End Organ Function
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Renal function
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Liver function and presence of cirrhosis and hepatocellular carcinoma
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Presence of coagulopathy
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History of hepatitis B and C
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Nutritional status and protein-losing enteropathy
Immunologic
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Presence of antihuman leukocyte antigen antibodies
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Acquired immunodeficiency secondary to malnutrition and protein-losing enteropathy
Anatomic/Physiologic Considerations
Risk assessment and planning of the appropriate operative procedure require comprehensive evaluation of the patient’s anatomy and cardiopulmonary physiology. Complete documentation of systemic and pulmonary venous return is required. This must also include knowledge of hepatic venous return. Abnormalities of great vessel relationship should be noted but generally pose few problems for cardiac transplantation. Specific attention must be paid to branch pulmonary arterial anatomy. Stenoses, hypoplasia, distortions, and discontinuity of the pulmonary arteries are commonly present and may determine whether isolated heart transplantation can be achieved. Angiography and magnetic resonance imaging may be required for full evaluation. Assessment of systemic-to-pulmonary arterial shunts and collateral circulation is also critical. Persistence of major collateral vessels will cause an unnecessary left ventricular volume overload that may be poorly tolerated by the freshly ischemic cardiac allograft. Extensive systemic-to-pulmonary collateral circulation also represents an important risk factor for severe perioperative hemorrhage. Chronic secondary erythrocytosis and history of multiple prior thoracic surgical procedures add to the risk of perioperative bleeding. Reports of all prior operative procedures must be directly reviewed. It is not unusual to find important clinical information that directly affects surgical planning, such as a history of postoperative mediastinal or pleural infection or even unilateral pleurodesis that would likely preclude ipsilateral lung transplantation. History of phrenic nerve damage should also be sought. When doubt exists, diaphragmatic motion should be studied with ultrasonography or fluoroscopy. The relationship of conduits or cardiac structures to the posterior aspect of the sternum must also be noted, because inadvertent entry into a cavity must be avoided. Finally, evaluation for the presence of pulmonary arteriovenous malformations must be made in cyanotic patients, especially those with cavopulmonary anastomoses. Those at greatest risk are patients with a prior classic Glenn shunt and those with an underlying diagnosis of left isomerism. When the patient has complex heart disease with incomplete separation of circulations, it may be difficult to determine how much cyanosis is a result of this incomplete separation and how much is a result of the pulmonary arteriovenous malformations. If the latter is extensive, there will be obligatory cyanosis after isolated heart transplantation. This cyanosis may be poorly tolerated by the freshly hypoxic-ischemic donor myocardium. Microscopic arteriovenous malformations may resolve in the months following successful heart transplantation, but this is less likely when there are multiple and large such malformations.
Evaluation of pulmonary vascular resistance (PVR) is as important as the assessment of cardiac anatomy. The adult right ventricular myocardium, when rendered ischemic, may be less tolerant of elevated PVR than the pediatric myocardium. Cardiac transplantation in pediatric candidates has been successfully performed when indexed PVR is as high as 10 IU. This may not be feasible in adults, although few hard data are available in this area. The evaluation of PVR may be very difficult (if not impossible) in the setting of complex heart disease with shunts at the pulmonary arterial level and with discontinuous pulmonary arteries. In these complex settings, additional clinical information must be incorporated along with hemodynamic data (eg, intensity of continuous murmurs from systemic-to-pulmonary shunts and systemic oxygen saturations).
Medical Evaluation
Many adults with end-stage CHD have suffered years of ventricular failure and/or progressive cyanosis. Chronic erythrocytosis may be associated with bleeding diathesis. This may be exacerbated by liver dysfunction in the patient with chronic right-sided heart failure, especially long-term Fontan survivors. The latter group may progress to overt cirrhosis ; and, on rare occasions, hepatic adenomas and hepatocellular carcinoma may develop. Liver imaging should form part of the pretransplant evaluation of the late Fontan operation survivor, and in selected cases liver biopsy may be indicated. Platelet consumption in the lungs may occur in the patient with advanced pulmonary vascular disease, leading to severe thrombocytopenia in some cases. Long-standing low cardiac output may also lead to severe renal dysfunction. It may be hard to predict to what extent this will reverse after successful thoracic transplantation. Many patients operated on in earlier eras were exposed to hepatitis B and C viruses from contaminated blood products. When there is evidence of prior infection with these viruses, infectious disease and hepatology consults should be obtained to determine the risk of reactivation of these viruses when immunosuppression is introduced, and to evaluate for antiviral therapy. When there is a history of prior neurologic events (eg, stroke, cerebral abscess, or seizure disorder), pretransplant evaluation should include brain imaging. Nutritional status should also be carefully evaluated, because cardiac cachexia may be an important determinant of perioperative morbidity and survival. Low body mass index is common in the ACHD transplant candidate population. Cachexia may be particularly problematic in the patient with protein-losing enteropathy after Fontan operation and weight gain (because of fluid retention) may mask reduced lean body mass. There will be associated hypoalbuminemia, hypogammaglobulinemia, and lymphopenia. This can result in acquired immunodeficiency before transplantation and may contribute to the high posttransplant mortality in the Fontan patient.
Finally, it should be noted that the high number of pretransplant blood transfusions and the frequent prior usage of homograft material results in significant risk for the development of pretransplant antihuman leukocyte antigen (HLA) antibodies in this population. This increases the risk of hyperacute and accelerated early rejection, as well as the late risk of posttransplant coronary arterial disease and chronic graft dysfunction. For this reason, many centers require a negative prospective or “virtual” donor-specific cross-match before accepting organs for transplantation in adults with CHD who are sensitized against nonself HLA antigens. This may markedly decrease the chances of finding a suitable donor for patients who are highly sensitized.
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