Prevalence of iron deficiency and anemia in pediatric heart transplant recipients.

INTRODUCTION: The prevalence of iron deficiency and anemia in the setting of modern-day maintenance immunosuppression in pediatric heart transplant (HTx) recipients is unclear. The primary aim was to determine the prevalence of iron deficiency (serum ferritin < 30 ng/mL ± transferrin saturation < 20%) and anemia per World Health Organization diagnostic criteria and associated risk factors. METHODS: Single-center, cross-sectional analysis of 200 consecutive pediatric HTx recipients (<21 years old) from 2005 to 2021. Data were collected at 1-year post-HTx at the time of annual protocol biopsy. RESULTS: Median age at transplant was 3 years (IQR .5-12.2). The median ferritin level was 32 ng/mL with 46% having ferritin < 30 ng/mL. Median transferrin saturation (TSAT) was 22% with 47% having TSAT < 20%. Median hemoglobin was 11 g/dL with 54% having anemia. Multivariable analysis revealed lower absolute lymphocyte count, TSAT < 20%, and estimated glomerular filtration rate <75 mL/min/1.73 m2 were independently associated with anemia. Ferritin < 30 ng/mL in isolation was not associated with anemia. Ferritin < 30 ng/mL may aid in detecting absolute iron deficiency while TSAT < 20% may be useful in identifying patients with functional iron deficiency ± anemia in pediatric HTx recipients. CONCLUSION: Iron deficiency and anemia are highly prevalent in pediatric HTx recipients. Future studies are needed to assess the impact of iron deficiency, whether with or without anemia, on clinical outcomes in pediatric HTx recipients.

Fontan-associated liver disease after heart transplant.

BACKGROUND: Fontan associated liver disease (FALD) potentially impacts Fontan patients undergoing heart transplant. This multi-center study sought to identify pre-transplant risk factors and characterize any post-transplant liver recovery in those patients undergoing heart-alone transplant. METHODS: Review of Fontan patients at 12 pediatric institutions who underwent heart transplant between 2001-2019. Radiologists reviewed pre and post-transplant liver imaging for fibrosis. Laboratory, pathology and endoscopy studies were reviewed. RESULTS: 156 patients underwent transplant due to decreased ventricular function (49%), protein losing enteropathy (31%) or plastic bronchitis (10%); median age at transplant was 13.6 years (interquartile range IQR 7.8, 17.2) with a median of 9.3 years (IQR 3.2, 13.4) between the Fontan operation and transplant. Few patients had pre-transplant endoscopy (18%), and liver biopsy (19%). There were 31 deaths (20%). The median time from transplant to death was 0.5 years (95% Confidence Interval CI 0.0, 3.6). The five-year survival was 73% (95% CI 64%, 83%). Deaths were related to cardiac causes in 68% (21/31) and infection in 6 (19%). A pre-transplant elevation in bilirubin was a predictor of death. Higher platelet levels were protective. Immediate post-transplant elevations in creatinine, AST, ALT, and INR were predictive of death. Advanced liver fibrosis identified on ultrasound, computed tomography, or magnetic resonance imaging was not predictive of death. Liver imaging suggested some improvement in liver congestion post-transplant. CONCLUSIONS: Elevated bilirubin, but not fibrosis on liver imaging, was associated with post-heart transplant mortality in Fontan patients in this multicenter retrospective study. Additionally, heart transplant may alter the progression of FALD.

An ethical analysis of obesity as a determinant of pediatric heart transplant candidacy.

BACKGROUND: Inclusion of BMI as criterion in the determination of heart transplant candidacy in children is a clinical and ethical challenge. Childhood obesity is increasing and children with heart disease are not spared. Currently, many adult heart transplant centers consider class II obesity and higher (BMI > 35 kg/m2 ) to be a relative contraindication for transplantation due to risk of poor outcome after transplant. No national guidelines exist regarding consideration of BMI in pediatric heart transplant and outcomes data are limited. This leaves decisions about transplant candidacy in obese pediatric patients to individual institutions or on a case-by-case basis, allowing for bias and inequity. METHODS: We review (a) the prevalence of childhood obesity, including among heart transplant candidates, (b) the lack of existing BMI guidelines, and (c) relevant literature on BMI and pediatric heart transplant outcomes. We discuss the ethical considerations of using obesity as a criterion using the principles of utility, justice, and respect for persons. RESULTS: Existing transplant outcomes data do not show that obese children have different or poor enough outcomes compared to non-obese children to warrant exclusion. Moreover, obesity in the United States is unequally distributed by race and socioeconomic status. Children already suffering from health disparities are therefore doubly penalized if obesity denies them access to life-saving transplant. CONCLUSION: Insufficient data exist to support using any BMI cutoff as an absolute contraindication for heart transplant in children. Attention should be paid to health equity issues when considering excluding a patient for transplant based on obesity.

Assessment of rejection risk following subtherapeutic calcineurin inhibitor levels after pediatric heart transplantation.

CNIs are the mainstay of immunosuppressive therapy after pediatric HTx. While regular laboratory surveillance is performed to ensure blood levels are within targeted range, the risk of acute rejection associated with subtherapeutic CNI levels has never been quantified. This is a retrospective single-center review of 8413 CNI trough levels in 138 pediatric HTx recipients who survived >1 year after HTx. Subtherapeutic CNI levels were defined as <50% of the lower limit of target range. The risk of acute, late (>12 months post-transplant) rejection following recipients' subtherapeutic CNI levels was assessed using time-varying multivariable Cox proportional hazards analysis. We found that 79 of 138 recipients (57%) had at least one subtherapeutic CNI level on routine surveillance laboratories during a mean follow-up of 5.5 ± 3.6 years. Following an episode of subtherapeutic levels, 17 recipients (22%) had biopsy-proven rejection within the next 3 months; the majority (9/17) within the first 2 weeks. After presenting with subtherapeutic CNI levels, recipients incurred a 6.1 times increased risk of acute rejection in the following 3 months (HR = 6.11 [2.41, 15.51], P = <.001). Age at HTx, HLA sensitization, or positive crossmatch were not associated with acute late rejection, but rejection in the first post-transplant year was (HR 2.61 [1.27, 5.35], P = .009). Thus, maintaining therapeutic CNI levels is the most important factor in preventing acute rejection in recipients who are >12 months after pediatric HTx. Recipients who present with subtherapeutic CNI levels on surveillance monitoring are 6.1 times more likely to develop rejection in the following 3 months.

A fatal case of bortezomib-induced lung toxicity in a young adult heart transplant recipient.

Bortezomib is approved for the treatment of multiple myeloma but increasingly used in heart transplant (HTx) recipients with antibody-mediated rejection (AMR). Severe pulmonary toxicity is a rare complication in multiple myeloma patients treated with bortezomib, but has not been described in a solid organ transplant recipient. A 20-year-old man 7 years post-HTx presented with acute rejection with hemodynamic compromise. Endomyocardial biopsy showed mixed rejection (ISHLT grade 2R-3R acute cellular rejection (ACR) and pAMR 1 (I+) with diffuse C4d staining). Two new high MFI circulating MHC class-II donor-specific antibodies (DSA) were detected. Treatment included corticosteroids, antithymocyte globulin, plasmapheresis, IVIG, rituximab, and bortezomib (1.3 mg/m2 ). Due to rebound in DSA, a second course of bortezomib was started. Thrombocytopenia and peripheral neuropathy prompted a 50% dose reduction during the 2nd course. Shortly after the 3rd reduced dose, the patient developed hypoxemic respiratory failure. Bronchoscopy revealed pulmonary hemorrhage with negative infectious studies. Chest CT showed bilateral parenchymal disease with bronchiectasis and alveolar bleeding. Despite treatment with high-dose steroids, severe ARDS ensued with multisystem organ failure. The patient expired 23 days after the final dose of bortezomib. Post-mortem lung histology revealed diffuse alveolar damage, pulmonary fibrosis, and hemorrhage. Cardiac histology showed resolving/residual ACR 1R and pAMR 1 (I+). While rare, bortezomib-induced lung toxicity (BILT) can occur in HTx recipients and can carry a high risk of mortality. Drug reaction and immediate drug withdrawal should be considered in patients who develop respiratory symptoms, though optimal management of BILT is unclear.

Dopamine as a potential rescue therapy for refractory protein-losing enteropathy in Fontan-palliated patients.

PLE is an important cause of morbidity and mortality in patients who have undergone Fontan palliation. While multiple PLE therapies have been reported, none has proved consistently effective. Patients who do not respond to "standard" PLE therapies face poor long-term outcomes. We report here a significant response to dopamine infusion in three patients with chronic, refractory PLE. We hypothesize that this response may be at least partially due to a dopamine effect on lymphatic receptors rather than to an augmentation of cardiac output.

Functional Status and Quality of Life in Survivors of Extracorporeal Membrane Oxygenation After the Norwood Operation.

BACKGROUND: Infants who require extracorporeal membrane oxygenation (ECMO) support after a Norwood operation are at increased risk for early and late death compared with patients who do not require ECMO post-Norwood. Little is known about the effect that ECMO post-Norwood has on functional status and quality of life among long-term survivors. METHODS: We prospectively evaluated functional status and health-related quality of life in 12 surviving patients (cases) and 19 corresponding patients (controls) from a previous retrospective case-control assessment of long-term survival in patients requiring ECMO post-Norwood. Functional status was assessed with the Vineland Adaptive Behavior Scale-II, and health-related quality of life was assessed with the Pediatric Quality of Life Inventory (PedsQL) core and cardiac modules. RESULTS: There were no differences in demographics, extracardiac or genetic anomalies, or age at follow-up assessment between ECMO cases and non-ECMO controls. The Vineland Adaptive Behavior Scale-II scores were comparable between groups, with both groups demonstrating function in the normal range in all four domains tested. The only difference in PedsQL scores between cases and controls was perceived physical appearance, which was lower among ECMO survivors by both patient and proxy report. PedsQL scores of both groups were comparable to published scores for patients with single-ventricle congenital heart disease but generally lower than scores for the healthy population. CONCLUSIONS: The requirement for ECMO support after a Norwood operation does not appear to significantly affect functional status or quality of life among the subset of patients who achieve long-term survival.

Outcomes of third heart transplants in pediatric and young adult patients: analysis of the United Network for Organ Sharing database.

BACKGROUND: Repeat heart transplantation (re-HTx) is standard practice in many pediatric centers. There are limited data available on outcomes of third HTx after failure of a second graft. We sought to compare outcomes of third HTx in pediatric and young adult patients with outcomes of second HTx in comparable recipients. METHODS: All recipients of a third HTx in whom the primary HTx occurred before 21 years of age were identified in the United Network for Organ Sharing database (1985 to 2011) and matched 1:3 with a control group of second HTx patients by age, era and re-HTx indication. Outcomes including survival, rejection and cardiac allograft vasculopathy (CAV) were compared between groups. RESULTS: There was no difference between third HTx patients (n = 27) and control second HTx patients (n = 79) with respect to survival (76% vs 80% at 1 year, 62% vs 58% at 5 years and 53% vs 34% at 10 years, p = 0.75), early (<1 year from HTx) rejection (33.3% vs 44.3%, p = 0.32) or CAV (14.8% vs 30.4%, p = 0.11). Factors associated with non-survival in third HTx patients included mechanical ventilation at listing or HTx, extracorporeal membrane oxygenation support at listing or HTx, and elevated serum bilirubin at HTx. CONCLUSIONS: Outcomes among recipients of a third HTx are similar to those with a second HTx in matched patients, with no difference in short- or long-term survival and comparable rates of early rejection and CAV. Although the occurrence of a third HTx remains relatively rare in the USA, consideration of a third HTx appears reasonable in appropriately selected patients.

Risk factors for requiring extracorporeal membrane oxygenation support after a Norwood operation.

BACKGROUND: Patients requiring extracorporeal membrane oxygenation (ECMO) support after a Norwood operation constitute an extremely high-risk group. Data regarding risk factors for the requirement for ECMO post-Norwood are limited, however. We retrospectively assessed risk factors for requiring ECMO support after a Norwood operation during a 10-year period in a high-volume center. METHODS: Retrospective case-control study of 64 consecutive patients requiring ECMO support after a Norwood operation at a single institution during a 10-year period (January 2001-December 2010), with a 3:1 era-matched control group of patients who underwent a Norwood but did not require ECMO. RESULTS: In univariate analysis, ascending aorta less than 2.0 mm, longer cardiopulmonary bypass (CPB) time, intraoperative shunt revision, and right ventricle to pulmonary artery conduit were associated with the need for postoperative ECMO. A single left ventricle was protective compared with single right ventricle anatomy. By multivariate logistic regression, birth weight less than 2.5 kg and longer CPB time were independently associated with the need for postoperative ECMO. Receiver-operating characteristic curve analysis identified a peak lactate of 9 mmol/L and a peak vasoactive inotrope score (VIS) of 27 within 48 hours of surgery as most prognostic of the need for ECMO. CONCLUSIONS: Birth weight less than 2.5 kg and longer CPB time are independently associated with the need for ECMO after a Norwood operation. Peak serum lactate and peak VIS may be useful in stratifying risk for ECMO. Risk factors for ECMO post-Norwood appear to be similar to the risk factors for early mortality post-Norwood.

Survival through staged palliation: fate of infants supported by extracorporeal membrane oxygenation after the Norwood operation.

BACKGROUND: Infants supported by extracorporeal membrane oxygenation (ECMO) after a Norwood operation face in-hospital mortality rates of 60% to 70%. There are limited data on completion of staged palliation for the subset of patients who survive to hospital discharge. METHODS: We performed a retrospective case-control study of 64 sequential patients at a single institution supported by ECMO after a Norwood operation. Primary endpoints were survival to hospital discharge, stage II palliation, and stage III palliation. Predictors of non-survival to each endpoint were identified with logistic regression. Survival was compared with a 3:1 era-matched group of control patients who underwent a Norwood operation but did not require ECMO. RESULTS: Survival to hospital discharge, stage II palliation, and stage III palliation was 43.8%, 35.9%, and 25.4%, respectively for ECMO cases. Factors independently associated with non-survival to hospital discharge included female gender, ECMO 7 days or greater, and need for renal replacement therapy on ECMO. Non-Caucasian race and ECMO 7 days or greater were independently associated with non-survival to stage II, while non-Caucasian race, lower birth weight, and ECMO 7 days or greater were independently associated with non-survival to stage III. Extracorporeal membrane oxygenation was associated with decreased survival at each endpoint. Patients who survived ECMO had increased interstage mortality between hospital discharge and stage II palliation. CONCLUSIONS: Extracorporeal membrane oxygenation after a Norwood operation can be life-saving but ultimate survival through staged palliation remains suboptimal. The elevated mortality risk for patients supported by ECMO persists after hospital discharge. Both socioeconomic factors and ECMO-related morbidity may contribute to midterm mortality.

Tbx5-hedgehog molecular networks are essential in the second heart field for atrial septation.

The developmental mechanisms underlying human congenital heart disease (CHD) are poorly understood. Atrial septal defects (ASDs) can result from haploinsufficiency of cardiogenic transcription factors including TBX5. We demonstrated that Tbx5 is required in the second heart field (SHF) for atrial septation in mice. Conditional Tbx5 haploinsufficiency in the SHF but not the myocardium or endocardium caused ASDs. Tbx5 SHF knockout embryos lacked atrial septum progenitors. We found that Tbx5 mutant SHF progenitors demonstrated cell-cycle progression defects and that Tbx5 regulated cell-cycle progression genes including Cdk6. Activated hedgehog (Hh) signaling rescued ASDs in Tbx5 mutant embryos, placing Tbx5 upstream or parallel to Hh in cardiac progenitors. Tbx5 regulated SHF Gas1 and Osr1 expression, supporting both pathways. These results describe a SHF Tbx5-Hh network required for atrial septation. A paradigm defining molecular requirements in SHF cardiac progenitors for cardiac septum morphogenesis has implications for the ontogeny of CHD.

A novel murine allele of Intraflagellar Transport Protein 172 causes a syndrome including VACTERL-like features with hydrocephalus.

The primary cilium is emerging as a crucial regulator of signaling pathways central to vertebrate development and human disease. We identified atrioventricular canal 1 (avc1), a mouse mutation that caused VACTERL association with hydrocephalus, or VACTERL-H. We showed that avc1 is a hypomorphic mutation of intraflagellar transport protein 172 (Ift172), required for ciliogenesis and Hedgehog (Hh) signaling. Phenotypically, avc1 caused VACTERL-H but not abnormalities in left-right (L-R) axis formation. Avc1 resulted in structural cilia defects, including truncated cilia in vivo and in vitro. We observed a dose-dependent requirement for Ift172 in ciliogenesis using an allelic series generated with Ift172(avc1) and Ift172(wim), an Ift172 null allele: cilia were present on 42% of avc1 mouse embryonic fibroblast (MEF) and 28% of avc1/wim MEFs, in contrast to >90% of wild-type MEFs. Furthermore, quantitative cilium length analysis identified two specific cilium populations in mutant MEFS: a normal population with normal IFT and a truncated population, 50% of normal length, with disrupted IFT. Cells from wild-type embryos had predominantly full-length cilia, avc1 embryos, with Hh signaling abnormalities but not L-R abnormalities, had cilia equally divided between full-length and truncated, and avc1/wim embryos, with both Hh signaling and L-R abnormalities, were primarily truncated. Truncated Ift172 mutant cilia showed defects of the distal ciliary axoneme, including disrupted IFT88 localization and Hh-dependent Gli2 localization. We propose a model in which mutation of Ift172 results in a specific class of abnormal cilia, causing disrupted Hh signaling while maintaining L-R axis determination, and resulting in the VACTERL-H phenotype.