Determinants of Renal Function in Pediatric Heart Transplant Recipients: Long-term Follow-up Study

Acute Kidney Injury Requiring Dialysis After Pediatric Heart Transplant

BACKGROUND

Acute kidney injury (AKI) is a common complication of pediatric heart transplant, with a subset of patients developing severe AKI requiring dialysis (AKI-D). We aimed to identify the epidemiology, risk factors, and outcomes of postoperative AKI-D in pediatric heart transplant recipients.

METHODS

We retrospectively identified all pediatric first-time, single-organ heart transplants at our institution from 2014 to 2022. Postoperative AKI was defined as AKI within 2 weeks of transplant. Unadjusted and adjusted logistic regression were used to identify characteristics associated with AKI-D, and unadjusted time-to-event analyses were used to determine the association between AKI-D and survival free of kidney failure.

RESULTS

Among 177 patients included, 116 (66%) developed postoperative AKI of any stage, including 13 (7%) who developed AKI-D with median time from transplant to dialysis initiation of 6 days (IQR 3-13). In adjusted models, increased cardiopulmonary bypass time (OR 1.19, 95% CI 1.04-1.37, per 15 min increase in bypass time) and higher weight at transplant were associated with higher odds of AKI-D, whereas patient demographics and pretransplant kidney function were not associated with AKI-D. AKI-D was associated with greater mortality during initial hospitalization (46% vs. 1%, p < 0.001) and a lower rate of survival free of kidney failure.

CONCLUSIONS

The incidence of AKI-D after pediatric heart transplant was 7%, with extended cardiopulmonary bypass time associated with postoperative AKI-D even in adjusted models. Further research is needed to improve the prediction and management of AKI-D in this population.

mTor-inhibition within the first days after pediatric heart transplantation is a potentially safe option to prevent cardiac allograft vasculopathy

BACKGROUND

Immunosuppression after heart transplantation (HTX) with mammalian target of rapamycin (mTOR) inhibitors serves as a prophylaxis against rejection and to treat coronary vascular injury. However, there is little data on the early, preventive use of everolimus after pediatric HTX.

METHODS

Retrospective study of 61 pediatric HTX patients (48 cardiomyopathy and 13 congenital heart disease), 28 females, median age 10.1 (range 0.1-17.9) years transplanted between 2008 and 2020. We analyzed survival, rejection, renal function, occurrence of lymphoproliferative disorder, and allograft vasculopathy together with adverse effects of early everolimus therapy combined with low-dose calcineurin inhibitors.

RESULTS

Everolimus therapy was started at a median 3.9 (1-14) days after HTX. Median follow-up was 4.3 (range 0.5-11.8) years, cumulative 184 patient years. The estimated 1- and 5-year survival probability was 89% (CI 82%:98%) and 87% (CI 78%:97%). Four patients developed rejection (6.6%) (maximum 2R ISHLT criteria). No patient suffered from chronic renal failure. Three patients (4.9%) developed post-transplant lymphoproliferative disorder. Five patients suffered relevant wound-healing disorders after transplantation, four of them carrying relevant risk factors before HTX (mechanical circulatory support (n = 3), delayed chest closure after HTX (n = 3)). No recipient developed cardiac allograft vasculopathy.

CONCLUSION

Initiating everolimus within the first 14 days after HTX seems to be well tolerated, enabling a low incidence of rejection, post-transplant lymphoproliferative disorders, renal failure, and reveals no evidence of cardiac allograft vasculopathy as well as good overall survival in pediatric heart transplant recipients.

A quantitative assessment of renal function utilizing albuminuria in pediatric heart transplant recipients

INTRODUCTION

Kidney disease is common after pediatric heart transplantation. Serum creatinine-based glomerular filtration rate is the most frequently reported measure of kidney function. Albuminuria is an additional marker of kidney dysfunction and is not well described in this population. In this study, we evaluate the prevalence and degree of albuminuria and describe clinical factors associated with albuminuria in a cohort of pediatric heart transplant recipients.

METHODS

This was a cross-sectional study of pediatric heart transplant recipients. Albuminuria was assessed using spot urine albumin-to-creatinine ratio collected at the most recent annual screening cardiac catheterization through August 2019.

RESULTS

In 115 patients at a median duration of 10.2 years post-transplant, 39% had albuminuria. Stage 3 or greater chronic kidney disease was present in 6%. The immunosuppressive regimen at the time of measurement contained a calcineurin inhibitor (CNI) in 88% and a proliferation signal inhibitor (PSI) in 62%. In multivariable modeling, lower eGFR, PSI use, and younger age at transplant were associated with higher levels of albuminuria, whereas CNI use was associated with lower levels of albuminuria.

CONCLUSION

Albuminuria is a prevalent finding in medium-term follow up of pediatric heart transplant recipients, reflecting kidney injury, and is associated with other markers of kidney dysfunction, such as low eGFR. Younger age at transplant, lower eGFR, and PSI use were among the associations with albuminuria.

Identifying the association between tacrolimus exposure and toxicity in heart and lung transplant recipients: A systematic review

AIMS

Tacrolimus is the cornerstone of immunosuppression management in heart and lung transplant recipients, improving overall survival. However, tacrolimus-associated toxicities, including nephrotoxicity, neurotoxicity, new-onset diabetes mellitus after transplant (NODAT), and gastrointestinal toxicity, are known contributors to increased post-transplant morbidity outcomes and reduced graft and recipient survival rates. The aim of this systematic review was to identify correlations between pharmacokinetic measures of tacrolimus exposure in heart and lung recipients and tacrolimus toxicities.

METHODS

MEDLINE, Embase, the Cochrane Library, CENTRAL and WHO Clinical Trial Registries were searched for published studies evaluating tacrolimus toxicities and their correlation to pharmacokinetic monitoring parameters in thoracic transplant recipients. Studies were reviewed by two authors, with data extracted for evaluation. Risk of bias was assessed using the PEDro scale for randomised control trials and the Newcastle Ottawa Scale for non-randomised cohort studies.

RESULTS

Eighteen studies were eligible; a randomised control trial, 11 observational cohort studies, and 6 case series or studies. Of these, 9 studies were in heart transplant recipients alone and 5 in lung transplant recipients alone, 2 studies were in heart and lung transplant recipients and 2 were heart, lung, liver or renal transplant recipients. Studies used variable criteria to define toxicities. Tacrolimus trough concentration (C₀) was the marker of tacrolimus exposure most commonly used. Ten studies reported on nephrotoxicity. Elevated tacrolimus C₀ was associated with acute kidney injury occurrence and severity in three observational studies. Increasing C₀ was a predictor of renal impairment in 6 studies. One study found that for each 5 ng/mL per year of tacrolimus exposure, defined by consecutive AUC, eGFR declined by 1.3 mL/min/1.73m² (p < 0.001). Comparatively, 2 studies failed to find a significant association between nephrotoxicity and tacrolimus exposure. Seven studies reported on neurotoxicity, including neuro-encephalopathies, polyneuropathies and symptomatic change in neurological status. Neurotoxicity occurred both with tacrolimus C₀ within therapeutic range and with supratherapeutic C₀. No significant association was found between NODAT and tacrolimus C₀ in two studies. One study reported on gastrointestinal toxicity, with supratherapeutic C₀ and elevated peak concentration in one lung transplant recipient three days prior to symptom development.

CONCLUSION

No clearly defined relationship between tacrolimus exposure and toxicities is described in the literature. Studies with clear toxicity criteria and pharmacokinetic markers of tacrolimus exposure are required to provide valuable information that may optimise tacrolimus therapy, helping to reduce toxicities in heart and lung transplant recipients.

Longitudinal renal function in pediatric heart transplant recipients: 20-years experience

This study was initiated to assess the temporal trends of renal function, and define risk factors associated with worsening renal function in pediatric heart transplant recipients in the immediate post-operative period. We performed a single-center retrospective study in children ≤18 yr receiving OHT (1993-2012). The AKIN's validated, three-tiered AKI staging system was used to categorize the degree of WRF. One hundred sixty-four patients qualified for inclusion. Forty-seven patients (28%) were classified as having WRF after OHT. Nineteen patients (11%) required dialysis after heart transplantation. There was a sustained and steady improvement in renal function in children following heart transplantation in all age groups, irrespective of underlying disease process. The significant factors associated with risk of WRF included body surface area (OR: 1.89 for 0.5 unit increase, 95% CI: 1.29-2.76, p = 0.001) and use of ECMO prior to and/or after heart transplantation (OR: 3.50, 95% CI: 1.51-8.13, p = 0.004). Use of VAD prior to heart transplantation was not associated with WRF (OR: 0.50, 95% CI: 0.17-1.51, p = 0.22). On the basis of these data, we demonstrate that worsening renal function improves early after orthotopic heart transplantation.

Peri-operative kidney injury and long-term chronic kidney disease following orthotopic heart transplantation in children

Significant advances in cardiac intensive care including extracorporeal life support have enabled children with complex congenital heart disease and end-stage heart failure to be supported while awaiting transplantation. With an increasing number of survivors after heart transplantation in children, the complications from long-term immunosuppression, including renal insufficiency, are becoming more apparent. Severe renal dysfunction after heart transplant is defined by a serum creatinine level >2.5 mg/dL (221 μmol/L), and/or need for dialysis or renal transplant. The degree of renal dysfunction is variable and is progressive over time. About 3-10 % of heart transplant recipients will go on to develop severe renal dysfunction within the first 10 years post-transplantation. Multiple risk factors for chronic kidney disease post-transplant have been identified, which include pre-transplant worsening renal function, recipient demographics and morbidity, peri-transplant haemodynamics and long-term exposure to calcineurin inhibitors. Renal insufficiency increases the risk of post-transplant morbidity and mortality. Hence, screening for renal dysfunction pre-, peri- and post-transplantation is important. Early and timely detection of renal insufficiency may help minimize renal insults, and allow prompt implementation of renoprotective strategies. Close monitoring and pre-emptive management of renal dysfunction is an integral aspect of peri-transplant and subsequent post-transplant long-term care.

Empiric switch from calcineurin inhibitor to sirolimus-based immunosuppression in pediatric heart transplantation recipients

Sirolimus is used in heart transplant patients with CAV and CNI-induced nephropathy. However, little is known regarding the tolerability, rejection rate, and effect on renal function when used empirically in children. We describe our experience with the empiric use of a sirolimus-based immunosuppressive regimen in pediatric heart transplantation recipients. We reviewed records of patients in whom conversion was attempted to a CNI-free sirolimus-based regimen. Rejection episodes and measures of renal function were recorded. We attempted to convert 20 patients, of which 16 were successful. In total, six of 20 patients (30%) experienced adverse effects. Of the 16 converted, four patients converted to sirolimus due to CNI-induced disease (three nephropathy, one CAV), while 12 patients (mean age 5.5 yr, range 0.1-21 yr; 33% female; 33% with a history of congenital heart disease) were empirically switched to sirolimus at a mean of 2.3 yr after transplant. Follow-up was available for a mean of 2.5 yr after conversion (range 0.5-8.3 yr). The rate of rejection while taking CNIs was 0.18 rejection episodes per patient-year (total of five episodes), compared with 0.03 rejection episodes per patient-year (total of one episode) while on sirolimus. Renal function, in terms of GFR, significantly improved after sirolimus conversion at latest follow-up (from 86 ± 37 mL/min to 130 ± 49 mL/min, p = 0.02). Here, we demonstrate the potential benefit of empiric use of sirolimus in pediatric heart transplant patients in a CNI-free regimen. Larger and longer studies are needed to further clarify risks of rejection and adverse effect profiles.

Renal complications following lung and heart-lung transplantation

As survival improves after lung and heart-lung transplants, the long term detrimental impact of current management on renal function becomes more apparent as the number of non-renal solid organ transplant recipients on renal transplant waiting lists increases. Progressive chronic kidney disease (CKD) is a significant cause of morbidity and mortality in the transplant population. In this review we discuss the specific problems prior to lung or heart-lung transplant that predispose to CKD, as well as potential renal complications encountered during the peri- and post-transplant period. Significant acute and chronic nephrotoxicity is caused by calcineurin inhibitors (CNI). Mechanisms to decrease CNI exposure exist but have yet to be adopted in routine clinical care. Modifiable risk factors and the current screening and management approach taken at our institution are described. Pediatric nephrologists should be involved from an early stage. Future work will need to focus on identifying more accurate measures of renal function, given the limitations of current glomerular filtration rate estimation equations in a population where nutritional status may rapidly change post transplant. Multicentre studies of CNI minimisation strategies are required to guide future therapy that aims to minimise CKD development and progression in this vulnerable population.

Calcineurin inhibitor minimization using sirolimus leads to improved renal function in pediatric heart transplant recipients

The introduction of cyclosporine revolutionized the practice of immunosuppression for solid organ transplant recipients, and has resulted in a significant increase in survival. While CNI use has been the mainstay of immunosuppressive therapy in pediatric heart transplantation, CNIs have been associated with an increased risk of nephropathy leading to significant morbidity and mortality. We evaluated the effect on renal function of a CNI minimization protocol using SRL in pediatric heart transplant patients with CNI induced renal insufficiency. An IRB approved retrospective chart review and case control study was performed. There were 20 patients identified with renal insufficiency who had been converted to SRL (target 5-8 ng/mL) and cyclosporine (target 50-75 vs. 125-150 ng/mL). Renal insufficiency was defined as isotopic (Indium 111 DTPA) GFR <60 mL/min per 1.73 m(2) or sCr >1 mg/dL. Outcome variables evaluated were GFR and sCr at time of conversion and at two yr post conversion. Comparison was made with case control subjects matched for age at Tx, time from Tx to conversion, and initial GFR. The median age at Tx = 81 days (S.D. ±26), median time of conversion after Tx = 10 yrs (s.d. ±0.65). Self-limited/treatable side effects included hypercholesterolemia (10), neutropenia (6), aphthous ulcer (3), edema (2), anemia (2), and tremor (1). One patient rejected in the two yr prior to conversion, and one patient had two rejection episodes following conversion. GFR at conversion for study group was 51 ± 14 vs. 60 ± 2 at two yr, p = 0.018. GFR at inclusion for control group was 56 ± 20 vs. 53 ± 21, p = 0.253. This report demonstrates that minimizing CNI exposure by addition of SRL to the immunosuppressant regimen in pediatric heart transplant recipients result in improved renal function in comparison to historically managed patients. Furthermore, immunotherapy with SRL and lower-dose CNI can effectively prevent rejection with an acceptable side-effect profile.

Risk factors for late renal dysfunction after pediatric heart transplantation: a multi-institutional study

Renal dysfunction is a major determinant of outcome after HTx. Using a large, multi-institutional database, we sought to identify factors associated with late renal dysfunction after pediatric HTx. All patients in the PHTS database with eGFR ≥60 mL/min/1.73 m(2) at one yr post-HTx (n = 812) were analyzed by Cox regression for association with risk factors for eGFR <60 mL/min/1.73 m(2) at >1 yr after HTx. Freedom from late renal dysfunction was 71% and 57% at five and 10 yr. Multivariate risk factors for late renal dysfunction were earlier era of HTx (HR 1.84; p < 0.001), black race (HR 1.42; p = 0.048), rejection with hemodynamic compromise in the first year after HTx (HR 1.74; p = 0.038), and lowest quartile eGFR at one yr post-HTx (HR 1.83; p < 0.001). Renal function at HTx was not associated with onset of late renal dysfunction. Eleven patients (1.4%) required chronic dialysis and/or renal transplant during median follow-up of 4.1 yr (1.5-12.6). Late renal dysfunction is common after pediatric HTx, with blacks at increased risk. Decreased eGFR at one yr post-HTx, but not at HTx, predicts onset of late renal dysfunction. Future research on strategies to minimize late renal dysfunction after pediatric HTx may be of greatest benefit if focused on these subgroups.

Cystatin C and neutrophil gelatinase-associated lipocalin as markers of renal function in pediatric heart transplant recipients

We hypothesized that use of Schwartz formula underestimates the prevalence of CKD in PHT recipients. This study determined the prevalence and risk factors for CKD in PHT using novel methods-serum cystatin C, CKiD formula, Revised Schwartz formula, s- and u-NGAL. Serum BUN, creatinine, cystatin C and s- and u-NGAL were measured after prospective enrollment. Schwartz formula GFR was compared with novel methods. CKD was defined as CKiD GFR < 90 mL/min/1.73 m(2) . The s- and u-NGAL were compared between those with and without CKD. Potential risk factors for CKD were analyzed. Seventy-nine patients (46 male children or boys), mean age 9.9 ± 5.8 yr formed the study cohort. The prevalence of mild and moderate CKD was 2- to 3-fold higher using novel methods compared to Schwartz formula. u-NGAL and u-NGAL/Cr were significantly higher in patients with CKD. u- and s-NGAL had negative correlation with estimates of GFR. Women were at a higher risk for CKD (odds ratio 8.7) as was longer duration since transplant (p = 0.009). In conclusion, use of novel methods of GFR estimation unmasked 2- to 3-fold increased prevalence of CKD in PHT. Women and those with longer duration since transplant are at higher risk for CKD.

Nonimmune complications after transplantation

As posttransplant longevity has increased, nonimmune complications related to the transplant and posttransplant course have emerged as important factors in defining long-term outcomes. The incidence of, and risk factors for these complications may vary by transplanted organ based on immunosuppressive protocols and preexisting risk factors. This article discusses the relevant nonimmune complications associated with posttransplant care, with a focus on risk factors and management strategies.

Heart transplantation in children

In the last 40 years, orthotopic heart transplantation has been established as a realistic treatment strategy for infants and children with severe forms of congenital heart disease and cardiomyopathy. The evaluation, management, and outcomes of these patients have continued to improve. These achievements have advanced pediatric cardiac transplantation and allowed more attention to be focused on improving quality of life after transplantation and reducing the long-term complications.

Late outcomes of pediatric heart transplantation are independent of pre-transplant diagnosis and prior cardiac surgical intervention

BACKGROUND

An increasing number of children are being referred for cardiac transplantation after (1) failing conventional corrective or palliative surgical reconstruction, (2) after stabilization with mechanical circulatory support devices, and (3) when primary graft failure or advanced cardiac allograft vasculopathy are established.

METHODS

The records of 417 infants and children (age range, 0-18 years) who underwent cardiac transplantation from November 1985 through December 2005 at Loma Linda University Children's Hospital were retrospectively reviewed. The pre-transplantation diagnosis was used to divide patients into 3 groups: primary cardiomyopathy (CM), 103; hypoplastic left heart syndrome (HLHS), 154; and other complex congenital heart disease (CCHD), 160. These groups were compared and analyzed for differences in early and late morbidity and mortality.

RESULTS

Operative mortality was significantly lower in the CM group compared with the HLHS (p < 0.02;) and CCHD groups (p < 0.01). Long-term actuarial recipient survival, however, was similar for all groups. The 15-year actuarial survival was 59% for the CM Group, 57% for the HLHS Group, and 50% for the CCHD Group. Actuarial survival after retransplantation is not statistically different from that with primary cardiac transplantation.

CONCLUSION

Although peri-operative survival was lower in infants and children with HLHS and CCHD compared with those with CM, long-term survival has been the same for all groups. Late survival after retransplantation was not statistically different than among those with primary cardiac transplantation.

Chronic kidney disease in children following lung and heart-lung transplantation

CKD is a major co-morbidity in pediatric lung transplant recipients. We report the prevalence of renal impairment post-lung transplant at a single center, using a modified, age-adjusted eGFR for the best approximation of true GFR, and investigated associations and possible predictors of decline in renal function post-transplant. Renal function was assessed by eGFR pre-transplant, three and 12 months post-transplant, and at last follow-up. Decline in renal function was analyzed as percentage fall in eGFR in two phases (0-3 and 3-12). Furthermore, we investigated impact of gender, age, pre-transplant diagnosis and renal function, transplant type, early post-transplant dialysis, and tacrolimus trough levels on decline in eGFR using multivariate analysis. Over a five-yr period, 30 transplants were performed. Mean eGFR pretransplant was 117 mL/min/1.73 m(2) (s.d. 35) with mean decline in eGFR during the first three months post-transplant of 33% (s.d. 31, p < 0.001). Thereafter, mean decline in eGFR was 8% (s.d. 18, p = 0.02). None of the factors assessed were significantly associated with decline in eGFR post-transplant. In conclusion, many children have decline in renal function following lung transplantation, particularly early post-transplant. Unlike in adults, we were unable to detect any predictors of renal impairment in pediatric lung transplant recipients.

The profile of renal function over time in a cohort of pediatric heart transplant recipients

To assess the burden over time of renal dysfunction in pediatric heart transplant patients using an objective measure on an annual basis for serial comparison. GFR was measured at regular interval by nuclear medicine scintigraphy. Results were analyzed in relation to age, time post-transplantation, gender, and average calcineurin-inhibitor dose for the first two months post-transplantation. Results were compared with cGFR using the Schwartz equation. A total of 91 patients (56 males) transplanted between 1990 and 2004 underwent 373 GFR measurements. Median age at transplantation was 3.3 yr (birth - 17.8). Median first GFR at 0.7 yr (0.1-4.1) post-transplant was normal (94 mL/kg/1.73 m(2)). Freedom from at least mild renal insufficiency was 84% and 33% at one and five years post-transplant. Females had better renal function early post-transplant (GFR 105 mL/min/1.73 m(2)) but an increased probability of an abnormal GFR over time. Higher calcineurin inhibitor dose in the first two months post-transplantation was associated with an increasing probability of an abnormal GFR over time. The cGFR overestimated the measured GFR by 33 +/- 26 mL/kg/1.73 m(2). Renal insufficiency is an important morbidity after pediatric transplantation with the majority of patients experiencing at least mild renal dysfunction. Calculated GFR significantly underestimates the burden of renal insufficiency in this patient population.

Donor-recipient race mismatch and graft survival after pediatric heart transplantation

BACKGROUND

Black recipient race has been shown to predict poorer graft survival after pediatric heart transplantation. We analyzed our single-center experience comparing graft survival by race and the impact of donor-recipient race mismatch.

METHODS

One hundred sixty-nine consecutive primary pediatric heart transplant patients were analyzed by donor and recipient race (white recipient, 99; black recipient, 60; other, 10). The groups were similar in preoperative characteristics. There were fewer donor-recipient race matches in blacks compared with whites (10 versus 71; p < 0.0001).

RESULTS

Although 30-day and 6-month graft survival was similar for black and white recipients (93.9% and 85.8% versus 93.3% and 83.3%, respectively), overall actuarial graft survival was significantly lower in blacks (p < 0.019). Blacks tended to have a higher incidence of positive retrospective crossmatch (n = 26, 43%) than whites (n = 29, 29%), but this was not statistically significant (p = 0.053). The median graft survival for black recipients was 5.5 years compared with 11.6 years for whites. Donor-recipient race mismatch predicted poorer graft survival (5-year graft survival 48.9% versus 72.3%; p = 0.0032). The median graft survival for donor-recipient race-matched patients was more than twice that for mismatched patients (11.6 years versus 4.4 years). Cox proportional hazard analysis showed that donor-recipient race mismatch neutralized the effect of race on graft survival.

CONCLUSIONS

Graft survival after pediatric heart transplantation is inferior for black recipients compared with white recipients. These differences may be explained by a high incidence of donor-recipient race mismatch, which also predicts poorer outcome for all racial groups with pediatric heart transplantation. These data may have implications for future donor allocation schemes.

Renal function impacts outcomes after intestinal transplantation

BACKGROUND

Although renal dysfunction (RD) has been commonly associated with poor outcome after other solid organ transplants, it has not been studied in detail after intestinal transplantation (ITx). Here we provide a detailed analysis of renal function after ITx, and identify predictors of post-ITx RD.

METHODS

A retrospective analysis of patients undergoing ITx from 1991 to 2006 was performed. For each patient, the estimated glomerular filtration rate (eGFR) was compared with the normal GFR for age and gender to obtain the percent of normal eGFR. Chi-square analysis and log-rank tests were used to identify categorical variables associated with RD (eGFR <75% of normal) and to determine if RD was predictive of post-ITx survival.

RESULTS

Sixty-eight transplantations were performed in 62 patients. Overall patient survival at 1 and 5 years was 78% and 56%, respectively. Renal dysfunction was observed in 16% of patients post-ITx. The most frequent predictors of post-ITx RD were preoperative eGFR less than 75% of normal, pre-ITx location in the intensive care unit, and high-dose tacrolimus immunotherapy. An eGFR less than 75% of normal at days 7, 28, and 365 was predictive of poor patient survival (P<0.05).

CONCLUSIONS

This study provides the first detailed analysis of renal function after ITx. We identified specific risk factors for the development of RD in the first year post-ITx and found a significant association of RD with decreased long-term survival. Given the strong correlation of RD with poor outcome, preserving renal function may be key to improving long-term outcomes in ITx recipients.