Risk factors for aborted cardiac arrest and sudden cardiac death in children with the congenital long-QT syndrome

BACKGROUND

The congenital long-QT syndrome (LQTS) is an important cause of sudden cardiac death in children without structural heart disease. However, specific risk factors for life-threatening cardiac events in children with this genetic disorder have not been identified.

METHODS AND RESULTS

Cox proportional-hazards regression modeling was used to identify risk factors for aborted cardiac arrest or sudden cardiac death in 3015 LQTS children from the International LQTS Registry who were followed up from 1 through 12 years of age. The cumulative probability of the combined end point was significantly higher in boys (5%) than in girls (1%; P<0.001). Risk factors for cardiac arrest or sudden cardiac death during childhood included corrected QT interval [QTc] duration > 500 ms (hazard ratio [HR]; 2.72; 95% confidence interval [CI], 1.50 to 4.92; P=0.001) and prior syncope (recent syncope [< 2 years]: HR, 6.16; 95% CI 3.41 to 11.15; P<0.001; remote syncope [> or = 2 years]: HR, 2.67; 95% CI, 1.22 to 5.85; P=0.01) in boys, whereas prior syncope was the only significant risk factor among girls (recent syncope: HR, 27.82; 95% CI, 9.72 to 79.60; P<0.001; remote syncope: HR, 12.04; 95% CI, 3.79 to 38.26; P<0.001). Beta-blocker therapy was associated with a significant 53% reduction in the risk of cardiac arrest or sudden cardiac death (P=0.01).

CONCLUSIONS

LQTS boys experience a significantly higher rate of fatal or near-fatal cardiac events than girls during childhood. A QTc duration > 500 ms and a history of prior syncope identify risk in boys, whereas prior syncope is the only significant risk factor among girls. Beta-blocker therapy is associated with a significant reduction in the risk of life-threatening cardiac events during childhood.

SCN5A variants in Japanese patients with left ventricular noncompaction and arrhythmia

Left ventricular noncompaction (LVNC) is a genetically heterogenous disorder. Mutations in the human cardiac sodium channel alpha-subunit gene (SCN5A) are involved in the pathophysiology of cardiac arrhythmias and cardiomyopathies. This study was performed to compare the frequency of SCN5A variants in LVNC patients with or without arrhythmias, and to investigate the relationship between variants and disease severity. DNA was isolated from the peripheral blood of 62 Japanese probands with LVNC, comprising 17 familial cases and 45 sporadic cases. Blood samples were screened for variants in SCN5A using single-strand conformational polymorphism analysis (SSCP) and DNA sequencing. Seven variants, rs6599230:G > A, c.453C > T, c.1141-3C > A, rs1805124:A > G (p.H558R), rs1805125:C > T (p.P1090L), c.3996C > T, and rs1805126:T > C were identified in 7 familial and 12 sporadic cases. The frequency of SCN5A variants was significantly higher in the patients with arrhythmias than those without (50% vs 7%: P = 0.0003), suggesting these variants represent a risk factor for arrhythmia and supporting the hypothesis that genes encoding ion channels are involved in LVNC pathophysiology. The LVNC patients with heart failure also had high occurrence of SCN5A variants, suggesting the presence of SCN5A variants and/or arrhythmias increase the severity of LVNC.

The efficacy of mitral valve surgery in children with dilated cardiomyopathy and severe mitral regurgitation

Severe mitral regurgitation predicts poor outcomes in adults with left ventricular dysfunction. Frequently, adult patients now undergo initial mitral valve surgery instead of heart transplant. Pediatric data are limited. This study evaluates the efficacy of mitral valve surgery for severe mitral regurgitation in children with dilated cardiomyopathy. This is a single-institution experience in seven children (range, 0.5-10.9 years) with severe mitral regurgitation and dilated cardiomyopathy who underwent mitral valve surgery between January 1988 and February 2005, with follow-up to January 2006. Children with dilated cardiomyopathy had a depressed fractional shortening preoperatively (24.4% +/- 6.1%) that remained depressed (22.9% +/- 7.6%) 1.3 +/- 1.2 years after surgery (p = 0.50). Left ventricular end-diastolic (6.5 +/- 1.5 to 4.8 +/- 1.8 z-scores, p < 0.01) and end-systolic (6.8 +/- 1.5 to 5.5 +/- 2.1 z-scores, p < 0.05) dimensions improved. Hospitalization frequency had a median decrease of 6.0 hospitalizations per year (p < 0.02). Three patients were transplanted 0.2, 2.4, and 3.5 years after surgery. There was no perioperative mortality. Mitral valve surgery in children with dilated cardiomyopathy was performed safely and improved symptoms, stabilizing ventricular dysfunction in most patients. Mitral valve surgery should be considered prior to heart transplant in children with dilated cardiomyopathy and severe mitral regurgitation.

Inherited arrhythmias: a National Heart, Lung, and Blood Institute and Office of Rare Diseases workshop consensus report about the diagnosis, phenotyping, molecular mechanisms, and therapeutic approaches for primary cardiomyopathies of gene mutations affecting ion channel function

The National Heart, Lung, and Blood Institute and Office of Rare Diseases at the National Institutes of Health organized a workshop (September 14 to 15, 2006, in Bethesda, Md) to advise on new research directions needed for improved identification and treatment of rare inherited arrhythmias. These included the following: (1) Na+ channelopathies; (2) arrhythmias due to K+ channel mutations; and (3) arrhythmias due to other inherited arrhythmogenic mechanisms. Another major goal was to provide recommendations to support, enable, or facilitate research to improve future diagnosis and management of inherited arrhythmias. Classifications of electric heart diseases have proved to be exceedingly complex and in many respects contradictory. A new contemporary and rigorous classification of arrhythmogenic cardiomyopathies is proposed. This consensus report provides an important framework and overview to this increasingly heterogeneous group of primary cardiac membrane channel diseases. Of particular note, the present classification scheme recognizes the rapid evolution of molecular biology and novel therapeutic approaches in cardiology, as well as the introduction of many recently described diseases, and is unique in that it incorporates ion channelopathies as a primary cardiomyopathy in consensus with a recent American Heart Association Scientific Statement.

Missense mutations in desmocollin-2 N-terminus, associated with arrhythmogenic right ventricular cardiomyopathy, affect intracellular localization of desmocollin-2 in vitro

Background

Mutations in genes encoding desmosomal proteins have been reported to cause arrhythmogenic right ventricular cardiomyopathy (ARVC), an autosomal dominant disease characterised by progressive myocardial atrophy with fibro-fatty replacement.

We screened 54 ARVC probands for mutations in desmocollin-2 (DSC2), the only desmocollin isoform expressed in cardiac tissue.

Methods

Mutation screening was performed by denaturing high-performance liquid chromatography and direct sequencing.

To evaluate the pathogenic potentials of the DSC2 mutations detected in patients affected with ARVC, full-length wild-type and mutated cDNAs were cloned in eukaryotic expression vectors to obtain a fusion protein with green fluorescence protein (GFP); constructs were transfected in neonatal rat cardiomyocytes and in HL-1 cells.

Results

We identified two heterozygous mutations (c.304G>A (p.E102K) and c.1034T>C (p.I345T)) in two probands and in four family members. The two mutations p.E102K and p.I345T map to the N-terminal region, relevant to adhesive interactions.

In vitro functional studies demonstrated that, unlike wild-type DSC2, the two N-terminal mutants are predominantly localised in the cytoplasm.

Conclusion

The two missense mutations in the N-terminal domain affect the normal localisation of DSC2, thus suggesting the potential pathogenic effect of the reported mutations. Identification of additional DSC2 mutations associated with ARVC may result in increased diagnostic accuracy with implications for genetic counseling.

Safety and efficacy of nesiritide in pediatric heart failure

BACKGROUND

We hypothesized that recombinant B-type natriuretic peptide (BNP) (nesiritide) could improve urine output and neurohormonal markers of heart failure without worsening renal function in pediatric patients.

METHODS AND RESULTS

We analyzed our experience involving 140 nesiritide infusions in 63 consecutive children. Serum levels of BNP and electrolytes were measured before and after therapy. Dosing was begun at 0.01 mcg.kg.min without a bolus and titrated to a maximum of 0.03 mcg.kg.min, in 0.005-mcg.kg.min increments. Blood pressure, heart rate, and heart rhythm were monitored. In a substudy, 20 patients with decompensated cardiomyopathy-related heart failure received 72 hours of nesiritide with prospective assessment of aldosterone, norepinephrine, plasma renin, and endothelin-1 levels before and after therapy. The heart rate decreased significantly (P = .001). Urine output increased significantly on Days 1 and 3 (P < or = .001 and .004, respectively). The mean serum creatinine level decreased from 1.135 to 1.007 mg/dL (P < or = .001). In the substudy, aldosterone levels decreased from 37.5 +/- 57.1 to 20.5 +/- 41.9 ng/dL (P = .005). Plasma renin, norepinephrine, and endothelin-1 levels decreased nonsignificantly. Two infusions were discontinued because of hypotension.

CONCLUSIONS

Nesiritide safely treated decompensated heart failure in children. Increased urine output reflected improving renal function. Improved neurohormonal markers were seen after 72 hours of therapy, and complications were uncommon.

Concentrations of brain natriuretic peptide in the plasma predicts outcomes of treatment of children with decompensated heart failure admitted to the Intensive Care unit

OBJECTIVES

It is known that levels of brain natriuretic peptide predict outcomes of treatment for adults with decompensated heart failure. We hypothesized that it could predict outcomes in children with this condition.

METHODS

We divided retrospectively 82 patients with serial measurements of brain natriuretic peptide into 3 groups: those who survived and did not need readmission within less than 60 days; those who survived but needed readmission within less than 60 days; and those who died in hospital or within less than 60 days. Initial and final levels of the peptide correlated with adverse outcomes.

RESULTS

The percent change in level of the peptide was minus 78 percent, minus 38 percent, and 138 percent in the readmission-free group, the readmitted, and nonsurviving groups, respectively. Final levels were significantly lower in the readmission-free group than in the readmitted and nonsurviving groups (p equals 0.013 and p is less than 0.00001, respectively) and in the readmitted group than in the nonsurvivors (p equals 0.013). On univariate analysis, the final level, the change in level, and the percentage change in level significantly predicted outcomes (p equals 0.0002, 0.0072 and 0.0005, respectively). On multivariate analysis, only the final level of the peptide significantly predicted outcomes (p equals 0.01).

CONCLUSIONS

A final level of brain natriuretic peptide of greater than or equal to 760 picograms per millilitre strongly predicted an adverse outcome. Patients with higher final levels may be at higher risk of death and readmission, suggesting that this variable effectively predicts the response to treatment and prognosis in children with heart failure.

Effect of Body Mass Index on Outcome in Pediatric Heart Transplant Patients

BACKGROUND

Obesity and cachexia are risk factors for adverse outcomes in adult transplant patients. However, little is known about the effects of body mass index (BMI) on outcomes in pediatric heart transplant patients.

METHODS

Patients > 2 years of age undergoing heart transplantation from 1985 to 2004 at our institution were included in this study. BMI was assessed at the time of transplant and at 1 year post-transplant. Long-term outcomes were assessed by weight group.

RESULTS

The cohort included 105 patients with a mean age at transplant of 9.6 +/- 5.3 years. The mean BMI percentile at the time of transplant was 39 +/- 34, with 22 (21%) patients underweight (< 5th percentile) and 8 (8%) patients overweight (> or = 95th percentile). Among patients surviving to 1 year (n = 92), the mean BMI percentile increased to 57 +/- 33 (p < 0.05). Overall graft survival was decreased in patients underweight at transplant, mean 6.7 years (95% confidence interval [CI] 3.6 to 9.9), vs normal weight patients, mean 10.6 years (95% CI 8.8 to 12.4) (p < 0.05). Patients overweight at transplant did not have decreased graft survival. Neither low nor high BMI at 1 year post-transplant was associated with adverse outcomes. On multivariate analysis, being underweight at transplant was an independent predictor of decreased graft survival (p = 0.03).

CONCLUSIONS

Weight gain was nearly universal post-transplant with only 4% of patients underweight at 1 year. In the small number of patients overweight at transplant, graft survival was similar to normal-weight patients. Conversely, being underweight at transplant was an independent predictor of decreased graft survival.

Clinical aspects of type-1 long-QT syndrome by location, coding type, and biophysical function of mutations involving the KCNQ1 gene

BACKGROUND

Type-1 long-QT syndrome (LQTS) is caused by loss-of-function mutations in the KCNQ1-encoded I(Ks) cardiac potassium channel. We evaluated the effect of location, coding type, and biophysical function of KCNQ1 mutations on the clinical phenotype of this disorder.

METHODS AND RESULTS

We investigated the clinical course in 600 patients with 77 different KCNQ1 mutations in 101 proband-identified families derived from the US portion of the International LQTS Registry (n=425), the Netherlands' LQTS Registry (n=93), and the Japanese LQTS Registry (n=82). The Cox proportional hazards survivorship model was used to evaluate the independent contribution of clinical and genetic factors to the first occurrence of time-dependent cardiac events from birth through age 40 years. The clinical characteristics, distribution of mutations, and overall outcome event rates were similar in patients enrolled from the 3 geographic regions. Biophysical function of the mutations was categorized according to dominant-negative (> 50%) or haploinsufficiency (< or = 50%) reduction in cardiac repolarizing I(Ks) potassium channel current. Patients with transmembrane versus C-terminus mutations (hazard ratio, 2.06; P<0.001) and those with mutations having dominant-negative versus haploinsufficiency ion channel effects (hazard ratio, 2.26; P<0.001) were at increased risk for cardiac events, and these genetic risks were independent of traditional clinical risk factors.

CONCLUSIONS

This genotype-phenotype study indicates that in type-1 LQTS, mutations located in the transmembrane portion of the ion channel protein and the degree of ion channel dysfunction caused by the mutations are important independent risk factors influencing the clinical course of this disorder.

Mutations in PDLIM3 and MYOZ1 encoding myocyte Z line proteins are infrequently found in idiopathic dilated cardiomyopathy

Dilated cardiomyopathy (DCM), characterized by ventricular dilation and decreased systolic function, is estimated to be of genetic origin in up to 50% of cases. In the present study, we investigated the role of two genes, encoding the Z line proteins PDZ and LIM domain protein 3 (PDLIM3) and myozenin-1 (MYOZ1), in the etiology of DCM. The coding regions of PDLIM3 and MYOZ1 were first amplified from the genomic DNA of 185 unrelated DCM patients by polymerase chain reaction (PCR), followed by denaturing high-performance liquid chromatography (DHPLC) analysis. The samples that exhibited abnormal peaks on DHPLC were re-amplified, purified and sequenced using a Big-Dye Terminator cycle sequencing system. Interestingly, a 2-bp insertion (178insCA) in exon 2 of PDLIM3 was identified in one patient who presented with DCM during pregnancy and died a year later awaiting heart transplant. No other significant mutations were found in either PDLIM3 or MYOZ1. The mutation probably resulted in an unstable protein, since no exogenous protein could be detected in transfected murine myoblastoid cells by immunohistochemical or Western blot analyses. We conclude that mutations in PDLIM3 and MYOZ1, encoding myocyte Z line proteins, do not play any significant role in the genetic etiology of idiopathic DCM. The exact mechanism by which the mutation identified in the present study is linked to DCM phenotype remains unknown. The hemodynamic burden of pregnancy and/or other genetic or environmental factors could have precipitated heart failure symptoms in an individual with defective myocardial cytoarchitecture.

Over two decades of pediatric heart transplantation: How has survival changed?

OBJECTIVE

In 1984, the first successful infant heart transplant was performed at Texas Children's Hospital. This study analyzes the 21-year experience with pediatric heart transplantation at Texas Children's Hospital to assess whether and how survival has changed over time.

METHODS

Between November 1, 1984, and October 3, 2005, 164 consecutive orthotopic heart transplants were performed on 154 patients. Characteristics: mean age 7.1 +/- 6.0 years, mean body surface area 0.8 +/- 0.5 m(2). Diagnosis at transplant: cardiomyopathy 53.0% (n = 87), congenital heart defect 39.0% (n = 64), retransplant 7.9% (n = 13). Multivariate risk factor analysis of 32 variables was completed by Cox proportional hazards regression models.

RESULTS

Mean follow-up was 5.9 +/- 4.8 years. Overall Kaplan-Meier survival was 82% at 1 year, 65% at 5 years, and 54% at 10 years. After 1995, Kaplan-Meier survival (91% at 1 year and 71% at 5 years) was significantly improved over pre-1995 survival (71% at 1 year, 57% at 5 years, and 48% at 10 years; P =.026). Hospital survival improved in the post-1995 era (96%) compared with the pre-1995 era (77%; P < .001). Life-table analysis by yearly increments demonstrates only an improved survival (pre-1995, 71% -->post-1995, 91%) in the first posttransplant year (P = .001); every subsequent year the mortality rates are the same (P = .92). Risk factors for overall mortality are prolonged postoperative intubation (>5 days) and longer cardiopulmonary bypass time.

CONCLUSIONS

Primarily attributable to an increase in early survival, overall pediatric heart transplant survival is improved. However, after the first posttransplant year, the rate of mortality has not changed in 21 years. This highlights the need for new therapies to treat children both with or in need of a heart transplant.

Long QT syndrome and pregnancy

OBJECTIVES

This study was designed to investigate the clinical course of women with long QT syndrome (LQTS) throughout their potential childbearing years.

BACKGROUND

Only limited data exist regarding the risks associated with pregnancy in women with LQTS.

METHODS

The risk of experiencing an adverse cardiac event, including syncope, aborted cardiac arrest, and sudden death, during and after pregnancy was analyzed for women who had their first birth from 1980 to 2003 (n = 391). Time-dependent Kaplan-Meier and Cox proportional hazard methods were used to evaluate the risk of cardiac events during different peripartum periods.

RESULTS

Compared with a time period before a woman's first conception, the pregnancy time was associated with a reduced risk of cardiac events (hazard ratio [HR] 0.28, 95% confidence interval [CI] 0.10 to 0.76, p = 0.01), whereas the 9-month postpartum time had an increased risk (HR 2.7, 95% CI 1.8 to 4.3, p < 0.001). After the 9-month postpartum period, the risk was similar to the period before the first conception (HR 0.91, 95% CI 0.55 to 1.5, p = 0.70). Genotype analysis (n = 153) showed that women with the LQT2 genotype were more likely to experience a cardiac event than women with the LQT1 or LQT3 genotype. The cardiac event risk during the high-risk postpartum period was reduced among women using beta-blocker therapy (HR 0.34, 95% CI 0.14 to 0.84, p = 0.02).

CONCLUSIONS

Women with LQTS have a reduced risk for cardiac events during pregnancy, but an increased risk during the 9-month postpartum period, especially among women with the LQT2 genotype. Beta-blockers were associated with a reduction in cardiac events during the high-risk postpartum time period.

Epidemiology and cause-specific outcome of hypertrophic cardiomyopathy in children: findings from the Pediatric Cardiomyopathy Registry

BACKGROUND

Current information on the epidemiology and outcomes of hypertrophic cardiomyopathy (HCM) in children is limited by disease diversity and small case series.

METHODS AND RESULTS

The Pediatric Cardiomyopathy Registry has collected prospective and retrospective data on children diagnosed with HCM since 1990. We identified the various causes of HCM in childhood and determined the relationship between outcomes, cause, and age at presentation. Of 855 patients <18 years of age with HCM, 8.7% (n=74) had inborn errors of metabolism, 9.0% (n=77) had malformation syndromes, 7.5% (n=64) had neuromuscular disorders, and 74.2% (n=634) had idiopathic HCM. Children with HCM associated with inborn errors of metabolism and malformation syndromes have significantly worse survival than the other 2 groups. Patients with idiopathic HCM diagnosed before 1 year of age (n=227) had worse survival from the time of diagnosis than those diagnosed after 1 year of age (n=407). Patients with idiopathic HCM who survived to at least 1 year of age, however, had an annual mortality rate of 1% that was similar regardless of whether they were diagnosed before or after 1 year of age.

CONCLUSIONS

In children, HCM is a diverse disorder with outcomes that depend largely on cause and age. Patients presenting before 1 year of age have the broadest spectrum of causes and the poorest outcome. In those children with idiopathic HCM who survive beyond age 1, however, survival is independent of age at diagnosis, with an annual mortality rate (1%) that is much lower than previously reported in children and is not different from has been found in population-based studies in adults.

A common SCN5A variant alters the responsiveness of human sodium channels to class I antiarrhythmic agents

BACKGROUND

The potential pathophysiological role of common SCN5A polymorphisms in cardiac arrhythmias has been increasingly recognized. However, little is known about the impact of those polymorphisms on the pharmocological response of hNav1.5 to various antiarrhythmic agents.

METHODS AND RESULTS

The known SCN5A polymorphism, S524Y, was studied in comparison with the wild type (WT) in [corrected] the SCN5A-Q1077del variant. The ion channel gating kinetics and pharmacology were evaluated using whole-cell patch-clamp methods in HEK-293 cells. Consistent with a previous report, the basal ion channel gating kinetics of S524Y were indistinguishable from the WT. Quinidine (20 microM) caused similar extent of tonic block reduction of sodium currents at -120 mV in WT and S524Y. Surprisingly, quinidine (20 microM) exerted a more use-dependent block by a 10 Hz pulse train in S524Y than in WT at 22 degrees C (Ki: WT, 51.3 microM; S524Y, 20.3 microM). S524Y significantly delayed recovery from the use-dependent block, compared with the WT (tau= 88.6 +/- 7.9 s vs 41.9 +/- 6.6 s, P < 0.005). Under more physiological conditions using a 2 Hz pulse train at 37 degrees C, S524Y similarly enhanced the use-dependent block by quinidine. In addition, S524Y enhanced the use-dependent block by flecainide (12.5 microM), but not by mexiletine (100 microM).

CONCLUSION

A common SCN5A polymorphism, S524Y, can enhance a use-dependent block by class Ia and Ic antiarrhythmic agents. Our findings may have clinical implications in pharmacological management of cardiac arrhythmias since this common SCN5A polymorphism might be a contributing factor to the variable antiarrhythmic response.

Long QT syndrome in adults

OBJECTIVES

The aims of this study were: 1) to evaluate risk factors influencing the clinical course of mutation-confirmed adult patients with long QT syndrome (LQTS), 2) to study life-threatening cardiac events as a specific end point in adults, and 3) to examine the protective effect of beta-blocker therapy on cardiac events in adult LQTS patients with known cardiac channel mutations.

BACKGROUND

The clinical course and risk factors for cardiac events in genotype-confirmed adult patients with LQTS have not been previously investigated.

METHODS

The clinical characteristics of 812 mutation-confirmed LQTS patients age 18 years or older were studied with both univariate and multivariate analyses to determine the genotype-phenotype factors that influence the clinical course of adult patients with this disorder.

RESULTS

Female gender, corrected QT (QTc) interval, LQT2 genotype, and frequency of cardiac events before age 18 years were associated with increased risk of having any cardiac events between the ages of 18 and 40 years. Female gender, QTc interval > or =500 ms, and interim syncopal events during follow-up after age 18 years were associated with significantly increased risk of life-threatening cardiac events in adulthood. Beta-blockers provided a 60% reduction in risk of any cardiac event and life-threatening events, with somewhat greater effect in higher-risk subjects.

CONCLUSIONS

The severity of LQTS in adulthood can be risk stratified with information regarding genotype, gender, QTc duration, and history of cardiac events. Beta-blockers effectively reduce but do not eliminate the risk of both syncopal and life-threatening cardiac events in adult patients with mutation-confirmed LQTS.

Danon disease presenting with dilated cardiomyopathy and a complex phenotype

X-linked dilated cardiomyopathy (XLCM) was first described in 1987 and associated with dystrophin gene (DMD) mutations a decade later in one of the original two families. Here we report long-term follow-up of the second family (XLCM-2), for which a DMD mutation was never found. Analysis of the lysosome-associated membrane protein-2 (LAMP-2) gene detected a novel mutation, confirming a diagnosis of Danon disease. The broad phenotype in this family included dilated and hypertrophic cardiomyopathy, cardiac pre-excitation, skeletal myopathy with high serum creatinine kinase, cognitive impairement (in males), and and a pigmentary retinopathy in affected females. Cardiac biopsy in a 13-month-old mutation-carrying male showed no vacuolization by standard histology. We conclude that XLCM may be the presenting sign of Danon disease and, in the presence of familial history of HCM, pre-excitation, skeletal muscle involvement and retinal pigmentary dystrophy should prompt LAMP-2 clinical testing. Furthermore, the absence of vacuolar myopathy in biopsies from young patients may not exclude Danon disease.

Mechanical Circulatory Support as a Bridge to Combined Dual Organ Transplantation in Children

The use of mechanical circulatory support as a bridge to cardiac transplantation is now an accepted therapeutic option. Also, as the criteria for organ transplantation have broadened, multi-organ transplantation has become more feasible. We report the cases of 2 children with end-stage heart failure and renal failure who were successfully bridged to combined, single-donor heart and kidney transplantation with mechanical circulatory support.