The current state of, and future prospects for, cardiac transplantation in children

Variations in Criteria and Practices for Heart Transplantation Listing Among Pediatric Transplant Cardiologists

Ethical issues in pediatric heart transplantation (Htx) include resource allocation, benefit, and burden assessment in high-risk recipients, and informed consent. Practice patterns and decision-making was investigated using an internet survey with 47-multiple choice items and vignette-based questions. Of 43 pediatric Htx cardiologists contacted, 28 (65%) responded. Respondents reported that an overall median 1-month survival of 73% (range 50-100%), 1-year survival of 70% (range 50-85%), 5-year survival of 50% (range 40-85%), and 10-year survival of 50% (range 25-85%) was adequate to offer Htx. Based on vignettes presented, 100% of those surveyed would offer Htx to a straightforward 12-year old with end-stage dilated cardiomyopathy and a 7-year old with hypoplastic left heart syndrome with protein losing enteropathy. Thirty percent of physicians would offer Htx to a patient status post a Fontan procedure with mutliple co-morbidities. Seventy-five percent of physicians would offer Htx despite proven non-adherence. Considerable variability exists in the practice patterns of pediatric heart transplant cardiologists with regards to decision-making while evaluating patients for listing. Disagreements among pediatric Htx cardiologists exist when there are concerns for non-adherence and associated multiple co-morbidities. Further work is needed to understand these variations and develop consensus for pediatric Htx organ allocation.

Transient severe tricuspid regurgitation after transplantation of an extremely oversized donor heart in a child-Does size matter? A case report

In pediatric heart transplantation, the size of the donor organ is an important criterion for organ allocation. Oversized donor hearts are often accepted with good results, but some complications in relation to a high donor-recipient ratio have been described. Our patient was transplanted for progressive heart failure in dilated cardiomyopathy. The donor-to-recipient weight ratio was 3 (donor weight 65 kg, recipient weight 22 kg). The intra-operative echocardiography before chest closure showed excellent cardiac function, no tricuspid valve regurgitation, and a normal central venous pressure. After chest closure, central venous pressure increased substantially and echocardiography revealed a severe tricuspid insufficiency. As other reasons for right ventricular dysfunction, that is, myocardial ischemia, pulmonary hypertension, and rejection, were excluded, we assumed that the insufficiency was caused by an alteration of the right ventricular geometry. After 1 week, the valve insufficiency regressed to a minimal degree. In pediatric heart transplant patients with a high donor-to-recipient weight ratio, the outlined complication may occur. If other reasons for right ventricular heart failure can be ruled out, this entity is most likely caused by an acute and transient alteration of the right ventricular geometry that may disappear over time.

Organizational structure and processes in pediatric heart transplantation: a survey of practices

Despite emerging literature on pediatric heart transplantation, there continues to be variation in current practices. The degree of variability among heart transplant programs has not been previously characterized. The purpose of this study was to evaluate organizational structure and practices of pediatric heart transplant programs. The UNOS database was queried to identify institutions according to volume. Coordinators from 50 institutions were invited to participate with a 70% response rate. Centers were grouped by volume into four categories. Some institutional practices were dominated by clear volume trends. Ninety-five percent of larger centers routinely transplant patients with known antibody sensitization and report a broader range and acuity of recipients. Ninety-four percent report problems with non-adherence. Sixty-nine percent of centers routinely require prospective crossmatches. There was dramatic variation in the use of steroids across all centers. Sixty-five percent of centers transition adolescents to an adult program. Prophylaxis protocols were also highly inconsistent. This survey provided a comprehensive insight into current practices at pediatric heart transplant programs. The results delineated remarkably variable strategies for routine aspects of care. Analysis of divergence along with uniformity across protocols is a valuable exercise and may serve as a stepping-stone toward ongoing cooperation and clarity for evidence-based practice protocols.

Working Together as a Team: Adolescent Transplant Recipients and Nurse Practitioners

Nurse practitioners are a critical part of the transplant team, enhancing the quality of patient care with their knowledge and skill with respect to disease-specific populations of patients. Adolescent transplant recipients are a vulnerable population and require specific considerations. Nurse practitioners can successfully tailor care to the adolescent developmental stages in order to promote quality of life, adherence to the medical regimen, and successful transition to adult transplant centers and to minimize risk-taking behaviors. Teamwork between the patient's family and the entire transplant team is important to optimize not only the patient's health but also to ensure quality of life after transplant. Adolescents can be especially challenging after transplant, given their complex and evolving psychosocial and cognitive development. Nurse practitioners are in a unique position to be central in adolescents' successful adaptation to their medical condition. Facilitating identification and management of medication-related side effects, awareness of emotional health and quality of life, adherence to the medical regimen, and eventual transition to adult caregivers all remain critically important steps in care that are ideally suited for advance practice leadership.

Immunosuppression therapy for pediatric heart transplantation

OPINION STATEMENT

Outcomes following cardiac transplantation in childhood continue to improve. Advances in immunosuppressive therapy over the past two decades likely have contributed to this trend. The evolution in the management of immunosuppression in children has been based on clinical experience rather than on evidence-based medicine; indeed, there have been no pivotal randomized controlled trials of any form of immunosuppression in pediatric thoracic transplantation. Important trends in immunosuppressive therapy and transplant outcomes have been obtained from large transplant registries. Several trends have been identified since the last review of this topic in this journal. First, there is increased knowledge of the pharmacodynamics and pharmacokinetics of immunosuppressive drugs in children, with notable advances in the field of pharmacogenomics. These studies help explain individual variations in drug exposure, efficacy, and adverse events. They also help explain racial and ethnic variations in drug metabolism and efficacy. Second, there have been clear trends in the use of specific immunosuppressive medications. Use of induction therapy, especially polyclonal T cell-depleting antibody preparations, has increased significantly in recent years. The calcineurin inhibitor (CNI) tacrolimus is being used as the cornerstone of maintenance therapy in lieu of cyclosporine in more and more centers. Mounting evidence suggests that use of adjunctive agents (notably mycophenolate mofetil [MMF]) may improve outcomes, including survival, suggesting that monotherapy with CNIs is not the ideal maintenance therapy. Despite its increased cost, MMF has largely replaced azathioprine as the adjunctive agent of choice. Inhibitors of the mammalian target of rapamycin (i.e., sirolimus and everolimus) have not yet assumed a major place as adjunctive agents, as their safety and efficacy have not been well established in children. With the improvements in immunosuppressive therapy, the justification for routine corticosteroid use is far from clear, and many centers have shown excellent outcomes with complete steroid avoidance. Third, there is increasing interest in the importance of anti-HLA antibodies as important risk factors for adverse graft and patient outcomes. This is generating intense interest in treatments that target B cells and plasma cells. Finally, there is increasing realization that the "one size fits all" approach to immunosuppressive therapy is an obsolete concept and that the ultimate goal is to tailor immunosuppressive therapy to the needs of the individual patient. The development of reliable biomarkers of the patient's immune response to the allograft will be essential for optimal individualized immunosuppressive management.

Strategies to prevent cellular rejection in pediatric heart transplant recipients

Despite more than 40 years' experience in pediatric heart transplantation, cellular rejection remains a significant cause of morbidity and mortality. In this review, strategies and agents to prevent acute cellular rejection are discussed. Strategies to prevent rejection are divided into two phases - induction and maintenance therapies. Currently, the most commonly used induction agents are polyclonal antibodies (rabbit or equine antithymocyte globulin) and interleukin-2 receptor antibodies (daclizumab or basiliximab). Induction therapies have reduced early rejection, are renal sparing, and can reduce corticosteroid exposure, but have not yet been shown to have a longer term survival benefit. Multiple maintenance immunosuppressants are available. Nearly all regimens include a calcineurin inhibitor (either ciclosporin [cyclosporine] or tacrolimus). Most combinations in pediatric heart transplantation include an antiproliferative agent (azathioprine, mycophenolate mofetil or, less commonly, sirolimus). Everolimus has seen increasing use in adult heart transplant patients in Europe but, to date, its use is rare in pediatric heart transplantation. The use of corticosteroids as a third agent is still common, but strategies to avoid or minimize their use are increasing. The 'best' combination of therapies varies between studies. By gaining a better understanding of individuals' genetic and environmental risk factors, we may in the future be able to better predict the course of cardiac allografts and enhance our ability to tailor immunosuppression to individual patient variables with the ultimate goal of inducing a state of immune tolerance.

Humoral Rejection after Pediatric Heart Transplantation: A Case Report

Humoral rejection was observed 2 years after heart transplantation in a 10-year-old African American girl with sickle cell disease. Hemodynamic compromise developed, and the patient started treatment with extracorporeal membrane oxygenation within 24 hours of admission. With cellular rejection initially believed to be the cause, administration of thymoglobulin and high-dose steroids was initiated. Human leukocyte antigen antibody analysis revealed high titers of donor-specific class I and II antibodies. Aggressive treatment for antibody-mediated rejection was started with plasmapheresis and administration of intravenous immune globulin and ritux-imab. The patient displayed clinical signs of infection and was treated with antimicrobial, antiviral, and antifungal agents. Computed tomography of the chest suggested asperigillous infection. The patient underwent a left upper lobectomy. The patient recovered and has done well, now 4 years after having received the heart transplant. Antibody-mediated rejection should be considered early in heart transplant patients presenting with hemodynamic compromise and may respond to aggressive antibody and B cell–directed therapy. Vigilance for secondary infections, especially during treatment for rejection, is crucial.

Acute right ventricular failure after pediatric cardiac transplant: predictors and long-term outcome in current era of transplantation medicine

OBJECTIVES

To identify pretransplant factors associated with postprocedural right ventricular failure and the relationship between right ventricular failure and long-term survival in children.

METHODS

Records were reviewed for children having heart transplantation from 2000 to 2006.

RESULTS

Right ventricular failure was identified by clinical and echocardiographic parameters in 33/129 (25%) recipients: dilated cardiomyopathy in 14/90 (15%), congenital heart disease in 11/27 (41%), and restrictive cardiomyopathy in 8/12 (66%). In 9 of 12 (75%), known elevated (reactive) pulmonary vascular resistance progressed to right ventricular failure. In a further 23/117 (20%) recipients, pulmonary vascular resistance within predefined acceptable range progressed to right ventricular failure. Multiple logistic regression analyses indicated elevated pulmonary vascular resistance (odds ratio 12.30; 95% confidence interval 2.73, 55.32; P = .001) and primary diagnosis, restrictive cardiomyopathy (odds ratio 9.21; 95% confidence interval 2.07, 41.12; P = .004), and congenital heart disease (odds ratio 4.07; 95% confidence interval 1.36, 12.19; P = .012) were strongly associated with right ventricular failure, but duration of heart failure, pretransplant mechanical support, donor status, and ischemic times were not. Treatment included inhaled nitric oxide in 28 (84%), mechanical support in 10 (31%), hemofiltration in 13 (40%), and retransplantation in 2. A Cox multiple regression model including: primary diagnosis, right ventricular failure, and elevated pulmonary vascular resistance indicated that only the latter was independently linked with eventual mortality (hazards ratio 5.45; 95% confidence interval 1.36, 21.96; P = .017).

CONCLUSIONS

Primary diagnosis and pretransplant elevated reactive pulmonary vascular resistance are both linked to the evolution of right ventricular failure. Pulmonary vascular resistance assessment in end-stage heart failure is challenging; therefore, avoidance of right ventricular failure may not always be possible. Aggressive early treatment may mitigate the effects of right ventricular failure: pretransplant elevated pulmonary vascular resistance was independently associated with long-term survival, but right ventricular failure was not.

Meta-analysis of medical regimen adherence outcomes in pediatric solid organ transplantation

BACKGROUND

Adherence to the medical regimen after pediatric organ transplantation is important for maximizing good clinical outcomes. However, the literature provides inconsistent evidence regarding prevalence and risk factors for nonadherence posttransplant.

METHODS

A total of 61 studies (30 kidney, 18 liver, 8 heart, 2 lung/heart-lung, and 3 with mixed recipient samples) were included in a meta-analysis. Average rates of nonadherence to six areas of the regimen, and correlations of potential risk factors with nonadherence, were calculated.

RESULTS

Across all types of transplantation, nonadherence to clinic appointments and tests was most prevalent, at 12.9 cases per 100 patients per year (PPY). The immunosuppression nonadherence rate was six cases per 100 PPY. Nonadherence to substance use restrictions, diet, exercise, and other healthcare requirements ranged from 0.6 to 8 cases per 100 PPY. Only the rate of nonadherence to clinic appointments and tests varied by transplant type: heart recipients had the lowest rate (4.6 cases per 100 PPY vs. 12.7-18.8 cases per 100 PPY in other recipients). Older age of the child, family functioning (greater parental distress and lower family cohesion), and the child's psychological status (poorer behavioral functioning and greater distress) were among the psychosocial characteristics significantly correlated with poorer adherence. These correlations were small to modest in size (r=0.12-0.18).

CONCLUSIONS

These nonadherence rates provide benchmarks for clinicians to use to estimate patient risk. The identified psychosocial correlates of nonadherence are potential targets for intervention. Future studies should focus on improving the prediction of nonadherence risk and on testing interventions to reduce risk.

Outcome after pediatric heart transplantation: two decades of a single center experience

BACKGROUND

Twenty years after the first successful pediatric heart transplantation (HTx), the long-term outcome of this population is still unknown. Current study analyzes our results in pediatric HTx population.

METHODS AND RESULTS

Between 1985 and 2005, we performed 604 HTx. Forty-three patients (7%) were less than 18-years old and six patients were less than 1-year old. Mean age at HTx was 9.7+/-6.3 years (38 days-18 years). Indications were: cardiomyopathy in 33 patients (76%), congenital in 9 (21%), tumor in 1 (3%). Chronic immunosuppression was Cyclosporine A and Azathioprine-based. Overall survival at Kaplan-Meier analysis (CI 95%) was 82.5% at 1-year post-HTx, 73.5% at 5 years, 72.2% at 10 years, 62.1% at 15 years, and 49.3% at 20 years, respectively. We had 14 deaths (32%): 7 within the first year after HTx (early mortality, EM), 7 occurred later (late mortality, LM). Causes of EM were: graft failure (43%), acute rejection (43%) and post transplant lymphoproliferative disease (14%). Causes of LM were: neoplasms (57%), infection (28%), graft vasculopathy (15%). At late follow-up, cardiac function, somatic and psycoaffective development were normal. Fifteen patients (34%) developed neoplasms, nine patients (21%) hypertension, and three patients (8%) developed kidney dysfunction. Neoplasms were found to be an independent predictor of outcome (p=0.039) (OR=7).

CONCLUSIONS

Overall survival in the pediatric population is better than adults' population (62.1 vs 48% at 15 years after HTx). Neoplasms were the main comorbidities and causes of LM: at multivariate analysis, their incidence was related with hematic Cyclosporine A levels after 10 years from HTx (p=0.01).

Heart and lung transplantation in children

During the past two decades, several advances have resulted in marked improvement in medium-term survival for infants and children undergoing heart transplantation. Unfortunately, progress has been less dramatic in the field of lung and heart-lung transplantation, where there is little evidence of improved outcomes. The procedures remain palliative and all transplant recipients are at risk for the adverse effects of non-specific immunosuppression, including infections, lymphoproliferative disorders, and non-lymphoid malignancies. In addition, current immunosuppressive agents have narrow therapeutic windows and exhibit a wide array of organ toxicities, posing special challenges for the young patient who must endure life-long immunosuppression. New immunosuppressive regimens have lowered the rates of acute rejection but appear to have had relatively little impact on the incidence of chronic rejection, the principal cause of late graft loss. The ultimate goal is to induce a state of donor-specific tolerance, wherein the recipient will accept the allograft indefinitely without the need for long-term immunosuppression. This quest is currently being realised in animal models of solid organ transplantation, and offers great hope for children undergoing heart and lung transplantation in the future.

Cardiac allograft vasculopathy in pediatric heart transplant recipients

Metabolic parameters for coronary allograft vasculopathy (CAV) have not been well defined in children. CAV (by angiography or autopsy) was studied in 337 heart recipients on a cyclosporine-based steroid-sparing regimen. Freedom from CAV for all was 79% at 10 years. Fifty-nine patients (18%) developed CAV at a mean of 6.5 +/- 3 years post-transplant. First year rejections were significantly higher in CAV, mean 2.3 vs. 1.4, P = 0.003, odds ratio (OR) 1.8. Rejection with hemodynamic compromise beyond 1 year post-transplant was associated with CAV, P < 0.001, OR 8.4. There was no significant correlation among human leukocyte antigen DR (HLA DR) mismatch, pacemaker use or homocysteine levels and the development of CAV. Maximum cholesterol and low density lipoprotein (LDL) levels were not significantly different. Neither diabetes nor hypertension was significant predictors of CAV on multivariate logistic regression analysis. In conclusion, frequent and severe rejection episodes may predict pediatric CAV. Neither glucose intolerance nor lipid abnormalities appeared to alter risk for CAV in this population.

Successful cardiac resynchronization therapy in a 9-year-old boy with dilated cardiomyopathy

Despite increasing clinical impact of cardiac resynchronization therapy (CRT) with av-synchronous biventricular pacing in adults with dilated cardiomyopathy (DCMP), an ejection fraction (EF) of less than 35% and left bundle branch block (LBBB), there is still only little experience in children. We report on a 9-year-old boy with histologically proven DCMP and LBBB who had fulfilled the criteria for heart transplantation (HTX) after cardiac decompensation including catecholamine therapy. A transvenous CRT pacing system was implanted without technical difficulties. The healing process was uneventful. With optimized AV-interval invasive evaluation during implantation indicated a 16% pulse pressure increase and a 63% augmentation of LV dp/dt by pacing the LV 20 ms prior to the RV. Tissue Doppler imaging demonstrated complete LV resynchronization. Physical capacity increased and HTX could be delayed.

Pediatric heart transplantation: immunosuppression and its complications

PURPOSE OF REVIEW

Advances in immunosuppression have contributed to the significant improvements in outcome for pediatric heart transplant recipients in the past two decades. The large increase in the number of available immunosuppressive agents in the past few years mandates that those caring for this complex group of patients remain up to date in this rapidly advancing field.

RECENT FINDINGS

In this review, we evaluate recent studies of immunosuppressive efficacy, end-organ toxicities, and side effects of nonspecific immunosuppression with currently used regimens. In addition, we examine new findings that attempt to define the genetic contribution to rejection profiles, immunosuppressive efficacy, and drug disposition after heart transplantation in children.

SUMMARY

The continuous evaluation of new immunosuppressive regimens will help to elucidate the optimal treatment regimens for pediatric heart transplant recipients. Unfortunately, the small number of transplantations means that it is unlikely that pivotal randomized, controlled trials will ever be performed in this population. Extrapolation from adult controlled trials and experience from other pediatric solid organ transplant recipient populations will continue to provide important contributions to our knowledge base. Understanding the genetic contribution to graft and patient outcomes may help us tailor immunosuppressive therapy for the individual patient.