Pediatric Coronary Allograft Vasculopathy-A Review of Pathogenesis and Risk Factors

Pediatric Combined Heart-liver Transplantation: A Single-center Long-term Experience

Background

Combined heart liver transplant (CHLT) continues to gain attention as a surgical treatment for patients with end-stage heart and liver disease but remains rare. We present our institutional longitudinal experience with up to 14 y of follow-up, focused on long-term outcomes in CHLT recipients.

Methods

We conducted a single-institutional, retrospective review from January 1, 2010, to December 31, 2023, including 7 patients ages 7-17 y who underwent CHLT.

Results

Most patients were surgically palliated via Fontan procedure pretransplant (n = 6), and all had evidence of advanced fibrosis or cirrhosis before transplant. The 30-d mortality was 14.3% (n = 1, multiorgan failure). During the follow-up period, 1 patient developed acute heart rejection which required treatment and 2 developed acute liver rejection. In all cases, rejection was successfully treated. Two patients developed acute heart rejection which did not require treatment (grade 1R). No patients developed chronic or refractory rejection. No patients developed allograft coronary artery vasculopathy.

Conclusions

CHLT remains a rarely performed treatment for pediatric patients with end-stage heart and liver disease, but our long-term data suggest that this treatment strategy should be considered more frequently.

Clinical approach to mechanical circulatory support in the transplant patient from the Pediatric Heart Transplant Society

The use of mechanical circulatory support (MCS) for pediatric patients who have undergone heart transplant has grown rapidly in the past decade. This includes support in the immediate post-transplant period and "rescue" therapy for patient later in their transplant course. Extracorporeal membrane oxygenation (ECMO) remains a standard modality of support for intraoperative concerns and for acute decompensation in the immediate post-transplant period. However, both pulsatile and continuous flow ventricular assist devices (VADs) have been used with increasing success in transplant patients for longer durations of support. Centers participating in the Pediatric Heart Transplant Society (PHTS) were queried to provide their internal protocols and rationale for mechanical circulatory support following heart transplant. These protocols coupled with evidence-based literature were used to provide the following description of clinical approaches to MCS in the transplant patient highlighting areas of both broad consensus and significant practice variation.

Patterns of Early Coronary Artery Changes in Pediatric Heart Transplant Recipients Detected Using Optical Coherence Tomography

BACKGROUND

Cardiac allograft vasculopathy, the leading cause of graft failure in pediatric heart transplant recipients, is characterized by diffuse and concentric coronary intimal thickening. Early treatment yields better outcomes. While coronary angiography is the standard for cardiac allograft vasculopathy screening and diagnosis, it only identifies luminal narrowing, which occurs in more severe disease. Coronary optical coherence tomography (OCT) is a high-definition intravascular imaging modality that may offer earlier diagnosis. We used OCT to investigate coronary intimal thickening in pediatric transplant recipients and examined its (1) location (ie, vessel type and location) and (2) nature (ie, characteristics of cross-sectional and longitudinal thickening).

METHODS

Sites collected coronary angiography and OCT data from participants (N=258 vessel segments from 73 individuals; median age: 11.5 years [8.4-15.3]; 55% male). Images were collected from the left anterior descending, left circumflex, and right coronary arteries, and location (ie, proximal, middle, and distal) were classified using coronary angiography.

RESULTS

OCT identified 32 vessel segments meeting criteria for significant thickening, 88% of which were angiographically silent. Longitudinal thickening was segmental rather than global in 88%, and cross-sectional thickening was 48% eccentric and 52% concentric. Intimal thickening prevalence and severity measures did not consistently differ between coronary artery type (P=1.000) or location (P=0.248) but increased with time since transplant and age at transplant and OCT procedure.

CONCLUSIONS

In pediatric transplant recipients, we observed a surprisingly high prevalence of segmental and eccentric intimal thickening. Insights from intravascular imaging suggest these patterns of coronary vascular changes may precede overt cardiac allograft vasculopathy. Identifying early changes may offer opportunity for enhanced surveillance and earlier intervention.

Pediatric heart transplantation: how to manage problems affecting long-term outcomes?

Since the initial International Society of Heart Lung Transplantation registry was published in 1982, the number of pediatric heart transplantations has increased markedly, reaching a steady state of 500-550 transplantation annually and occupying up to 10% of total heart transplantations. Heart transplantation is considered an established therapeutic option for patients with end-stage heart disease. The long-term outcomes of pediatric heart transplantations were comparable to those of adults. Issues affecting long-term outcomes include acute cellular rejection, antibody-mediated rejection, cardiac allograft vasculopathy, infection, prolonged renal dysfunction, and malignancies such as posttransplant lymphoproliferative disorder. This article focuses on medical issues before pediatric heart transplantation, according to the Korean Network of Organ Sharing registry and as well as major problems such as graft rejection and cardiac allograft vasculopathy. To reduce graft failure rate and improve long-term outcomes, meticulous monitoring for rejection and medication compliance are also important, especially in adolescents.

Early experience with pediatric cardiac transplantation in a limited resource setting

BACKGROUND

Pediatric heart transplantation is a now a well-established and standard treatment option for end stage heart failure for various conditions in children. Due to logistic issues, it is not an option for in most pediatric cardiac centres in the third world.

AIM

We sought to describe our early experience in the current era in India.

METHODS

This is a short term retrospective chart review of pediatric patients who underwent heart transplantation at our centre. Mean/Median with standard deviation /range was used to present data.

RESULTS

Twenty patients underwent orthotopic heart transplant between January 2016 and June 2019. The median age at transplant was 12.4years (range 3.3 to 17.3 years). The median weight was 23.2kg (range 10-80kg). The mean donor/recipient weight ratio was 1.62± 0.84. The mean ICU stay was 12.1days. The mean follow up post transplant was 2.03± 0.97years (range 10 days-3.57years). The 1 month and the 1 year survival was 100%. Biopsies were positive for significant rejection in 7 patients (35%). At the time of last follow-up, 3 patients (15%) had expired. The major post transplant morbidities were mechanical circulatory support (n=3), hypertension with seizure complex (n=3), post transplant lympho-proliferative disorder (n=1), pseudocyst of pancreas (n=1), coronary allograft vasculopathy (n=3) and systemic hypertension (n=7). All surviving patients (n=17) were asymptomatic at last follow up.

CONCLUSION

The results suggest acceptable short term outcomes in Indian pediatric patients can be achieved after heart transplantation in the current era. Significant rejection episodes and coronary allograft vasculopathy need careful follow up.

Percutaneous coronary intervention for coronary allograft vasculopathy with drug-eluting stent in Indian subcontinent: Issues in diagnosis and management

Coronary allograft vasculopathy fails to give a warning anginal pain due to denervation and often presents with acute coronary syndrome, ventricular dysfunction, or sudden cardiac death. Early diagnosis in a pediatric patient is difficult as it involves invasive coronary angiography or advanced imaging such as intravascular ultrasound or optical coherence tomography. A 12-year-old boy developed acute coronary syndrome, elevated troponins, and right bundle branch block, 5 years after cardiac transplantation and was treated with culprit-vessel angioplasty with a drug-eluting stent. Advanced imaging showed the involvement of nonculprit vessels too. In a detailed literature search, we failed to identify a similar clinical presentation and management in the subcontinent, hence our interest in publishing this report for educational value. Issues in diagnosis, management, prognosis, and prevention are discussed.

Multi-modal imaging of the pediatric heart transplant recipient

The assessment of pediatric patients after orthotropic heart transplantation (OHT) relies heavily on non-invasive imaging. Because of the potential risks associated with cardiac catheterization, expanding the role of non-invasive imaging is appealing. Echocardiography is fast, widely available, and can provide an accurate assessment of chamber sizes and function. Advanced echocardiographic methods, such as myocardial deformation, have potential to assess for acute rejection or cardiac allograft vasculopathy (CAV). While not currently part of routine care, cardiac magnetic resonance imaging (CMR) and computed tomography may potentially aid in the detection of graft complications following OHT. In particular, CMR tissue characterization holds promise for diagnosing rejection, while quantitative perfusion and myocardial late gadolinium enhancement may have a role in the detection of CAV. This review will evaluate standard and novel methods for non-invasive assessment of pediatric patients after OHT.

Using the Theory of Planned Behavior to Explore Pediatric Heart Transplant Recipients’ Dietary Behavior

Abstract. Heart transplantation is the treatment of choice for children with end-stage heart disease. Coronary artery vasculopathy is, however, a significant morbidity and leading cause of late graft loss, and hyperlipidemia a risk factor for its development. Improving diet in this population could have important benefits for patients. We wanted to understand what influences decisions about food intake in this patient group. Dietary intentions and behavior were examined using a questionnaire based on the Theory of Planned Behavior (TPB) with 67 children who had undergone heart transplantation at least 12 months previously. The TPB model was significant for both healthy and unhealthy dietary behaviors, explaining 55% and 38% of the variance, respectively. Ten percent of children reported not eating any fruit and/or vegetables in the previous week and only 29% reported eating fruit and/or vegetables every day. The Theory of Planned Behavior provides a framework for explaining some specific dietary behaviors related to individual food groups in children who have undergone heart transplantation. These preliminary data support using this approach to inform the development of interventions to improve fruit and vegetable consumption but the approach may be less useful for explaining and developing interventions to reduce the consumption of unhealthy foods.

Heart Transplant in Children: What a Primary Care Provider Needs to Know

Heart transplantation is offered to children with heart failure that is not amenable to medical or surgical therapy. Indications for heart transplant include unrepairable congenital heart disease, failed palliation of congenital heart disease, and cardiomyopathies. There has been tremendous progress in this field since the first heart transplant was performed in 1967. Each year, approximately 500 pediatric heart transplants take place worldwide. Pediatric heart transplant survivors are living longer with their initial transplant. Many pediatric practitioners are faced with caring for these patients before as well as after the heart transplant and, therefore, they should be knowledgeable about basic principles related to heart transplant. There are certain complications that are unique to this population, and medication side-effects, evaluation and management of a febrile illness, opportunistic infections, vaccination, pregnancy, and exercise recommendations are areas that require special consideration. [Pediatr Ann. 2018;47(4):e172-e178.].

Late graft dysfunction after pediatric heart transplantation is associated with fibrosis and microvasculopathy by automated, digital whole-slide analysis

BACKGROUND

Histopathologic features of late graft dysfunction (LGD) in endomyocardial biopsies (EMBs) after pediatric heart transplantation (HT) have been incompletely described and rarely quantified. We employed automated, morphometric analysis of whole-slide EMB images to objectively quantify fibrosis and microvasculopathy after pediatric HT.

METHODS

Nine recipients with clinical LGD were matched with controls on age, listing diagnosis, crossmatch and time since HT. Fibrosis was quantified as percent tissue area with fibrosis and capillary density as capillaries per unit area, number of capillary "neighbors" within 30 μm of each myocyte and myocyte-to-nearest-capillary diffusion distance. Clinical data, including all EMB reports, were also reviewed.

RESULTS

The groups were well matched for age at HT (median 4.0 vs 3.1 years), listing diagnosis (50% congenital heart disease for each), positive crossmatch (11% each) and days post-HT (2,628 vs 2,894, p = 0.69). Despite a similar number of previous EMBs (median 23 each, p = 0.43), areas occupied by fibrosis were greater in LGD cases (44.5% vs 23.2%, p = 0.012). Capillary number/area data were not statistically different between LGD cases and controls (378/mm² vs 559/mm², p = 0.57), but LGD cases more commonly had zero capillary neighbors (35% vs 20%, p = 0.02) and greater myocyte-to-nearest-capillary distances (27.1 μm vs 18.7 μm, p = 0.005). Cumulative rejection history correlated with fibrosis (r = 0.49, p = 0.039) and myocyte-to-nearest-capillary distance (r = 0.5, p = 0.036).

CONCLUSIONS

LGD after pediatric HT is associated with previous rejection and characterized histologically by fibrosis and microvasculopathy, which are not readily appreciated by traditional semi-quantitative EMB analysis. Software-assisted EMB analysis may enable greater pathophysiologic understanding of LGD and identification of targets for future study and intervention.

Interaction of older donor age and survival after weight-matched pediatric heart transplantation

BACKGROUND

Donors are matched for weight in pediatric heart transplantation (PHT), yet age differences are not considered in this decision. In this study we attempt to identify the effect of age differences in weight-matched patients and the effect these differences have on post-transplant survival.

METHODS

The United Network of Organ Sharing (UNOS) database was queried for the period from October 1987 to March 2014 for all pediatric heart transplant patients. Transplants with donor-to-recipient (D-R) weight ratios of 0.8 to 1.5 were identified (weight-matched). D-R age differences were categorized as: donors 5 years younger than recipients (D<R-5); donors within 5 years of recipients (D=R±5); and donors 5 years older than recipients (D>R+5).

RESULTS

A total of 4,408 patients were identified as weight-matched transplants. Of these transplants, 681 were D>R+5, 3,596 were D=R±5 and 131 were D<R-5. D>R+5 transplants were found to be associated with decreased post-transplant survival compared with D=R±5 (p = 0.002). Rates of acute rejection were similar among all groups but post-transplant coronary allograft vasculopathy (CAV) was more prevalent in D>R+5 than D=R±5 patients (28% and 18%, respectively; p < 0.001). Increasing age difference by each year was associated with decreasing median post-transplant survival time (p < 0.001; hazard ratio 1.018, range 1.011 to 1.025). The overall negative association with mortality was due to the adolescent cohort (11 to 17 years), specifically D>R+5 transplants, utilizing organs from donors >25 of age.

CONCLUSION

In PHT, increasing D-R age difference decreases survival; however, this effect is driven by recipients 11 to 17 years old and donors >25 years old. Allocation of younger donor organs to adolescent recipients should be a priority.

Use of sirolimus in pediatric heart transplant patients: A multi-institutional study from the Pediatric Heart Transplant Study Group

BACKGROUND

Proliferation signal inhibitors, such as sirolimus, are increasingly used in solid-organ transplantation. However, limited data exist on sirolimus-treated pediatric patients. We aimed to describe sirolimus use in pediatric heart transplant patients and test the hypothesis that sirolimus use is associated with improved outcomes.

METHODS

A retrospective review and propensity-matched analysis of the Pediatric Heart Transplant Study database was performed on patients undergoing primary heart transplantation from 2004 to 2013 with at least 1 year of follow-up comparing patients treated vs not treated with sirolimus at 1 year after transplant. The primary outcome of interest was patient survival, with secondary outcomes including cardiac allograft vasculopathy, rejection, malignancy, and renal insufficiency.

RESULTS

Between 2004 and 2013, 2,531 patients underwent transplantation. At least 1 year of follow-up was available for 2,080 patients, of whom 144 (7%) were on sirolimus at 1 year post-transplant. Sirolimus-treated and non-treated patients had similar survival in the overall cohorts and in the propensity-matched analysis. The secondary outcomes measures were also similar, including a composite end point of all outcome measures. There was a trend toward increased time to cardiac allograft vasculopathy (p = 0.09) and decreased time to infection (p = 0.05) among sirolimus-treated patients in the overall cohort (p = 0.19) but not in the propensity-matched cohort (p = 0.17).

CONCLUSIONS

Sirolimus was used in less than 10% of patients at 1 year post-transplant. Overall outcomes of sirolimus treated and non-treated patients were similar with respect to survival and major transplant adverse events. Further study of sirolimus in pediatric heart transplant patients is needed.

Heart Transplantation-The Pediatric Cardiac Critical Care Perspective

OBJECTIVES

Although there have been tremendous advancements in the care of severe pediatric cardiovascular disease, heart transplantation remains the standard therapy for end-stage heart disease in children. As such, these patients comprise an important and often complex subset of patients in the ICU. The purpose of this article is to review the causes and management of allograft dysfunction and the medications used in the transplant population.

DATA SOURCES

MEDLINE, PubMed, and Cochrane Database of systemic reviews.

CONCLUSIONS

Pediatric heart transplant recipients represent a complex group of patients that frequently require critical care. Their immunosuppressive medications, while being vital to maintenance of allograft function, are associated with significant short- and long-term complications. Graft dysfunction can occur from a variety of etiologies at different times following transplantation and remains a major limitation to long-term posttransplant survival.

Clinical Issues and Controversies in Heart Failure and Transplantation

Heart failure is a common problem among children admitted in the intensive care unit and is associated with significant morbidity and mortality. As such, the 2014 meeting of the Pediatric Cardiac Intensive Care Society included a session on Clinical Controversies in Heart Failure and Transplantation. This review contains the summaries of the podium presentations of this session and will cover some of the challenging aspects of caring for these patients including medical and mechanical support, fluid overload states, high-risk populations including those after heart transplantation, and end-of-life considerations.

Predictors of cardiac allograft vasculopathy in pediatric heart transplant recipients

CAV remains a leading cause of late graft loss and mortality among survivors of pediatric heart transplantation. We sought to define the incidence of CAV and identify its predictors in pediatric heart transplant recipients. The OPTN/UNOS database was analyzed for pediatric recipients who underwent heart transplant between 1987 and 2011. The primary end-point is time from heart transplantation to development of CAV (CAV-free survival). To identify predictors of CAV-free survival, demographic and transplant data were analyzed by the Kaplan-Meier survival method and Cox proportional hazards regression. Of 5211 pediatric heart transplant recipients with at least one-yr follow-up, the incidence of CAV at five, 10, and 15 yr was 13%, 25%, and 54%, respectively. Multivariate analysis found that risk of CAV was associated with the following variables: Recipient age 1-4 yr (HR 1.25), 5-9 yr (1.45), 10-18 yr (1.83), donor age >18 yr (1.34), re-transplantation (2.14), recipient black race (1.55), and donor cigarette use (1.54). Older recipient and donor age, recipient black race, donor cigarette use, and re-transplantation were highly associated with shorter CAV-free survival.