Post-transplant outcomes of children bridged to transplant with the Berlin Heart EXCOR Pediatric ventricular assist device.

BACKGROUND: Recent data suggest that Berlin Heart EXCOR Pediatric (EXCOR) ventricular assist device improves waiting list survival for pediatric heart transplant candidates. Little is known about their post-transplant outcomes. The aim of this analysis was to determine whether there was a difference in early survival for children bridged to transplant with EXCOR versus status 1A pediatric heart transplant patients not transplanted with ventricular assist device support. METHODS AND RESULTS: Pediatric heart transplant patients (n=106) bridged to transplantation with EXCOR were compared with a similarly aged cohort (n=1021) within the Organ Procurement and Transplant Network (OPTN) database (both cohorts from May 2007 to December 2010). In the EXCOR group, 12-month post-transplant survival (88.7%) was similar to OPTN patients listed status 1A who were not on ventricular assist device support at transplant (89.3%; P=0.85) and significantly better than 12-month survival in OPTN patients on extracorporeal membrane oxygenation at transplant (60.3%; P<0.001). Rejection (50%) was a significantly (P=0.005) higher cause of 12-month post-transplant mortality in the EXCOR compared with the OPTN group. Death after transplant was also higher in EXCOR patients with congenital heart disease compared with those with cardiomyopathy (26.1% versus 7.2%; P=0.02). Post-transplant survival was similar in EXCOR patients with ≥1 serious adverse event during ventricular assist device support as those without an event during support. CONCLUSIONS: The 12-month post-transplant survival with EXCOR is comparable with overall pediatric heart transplant survival and superior to survival after extracorporeal membrane oxygenation. Neither adverse events during support nor factors associated with mortality during support influence post-transplant survival. Rejection was a significantly greater cause of post-transplant mortality in EXCOR than in OPTN patients.

Waiting list mortality among children listed for heart transplantation in the United States.

BACKGROUND: Children listed for heart transplantation face the highest waiting list mortality in solid-organ transplantation medicine. We examined waiting list mortality since the pediatric heart allocation system was revised in 1999 to determine whether the revised allocation system is prioritizing patients optimally and to identify specific high-risk populations that may benefit from emerging pediatric cardiac assist devices. METHODS AND RESULTS: We conducted a multicenter cohort study using the US Scientific Registry of Transplant Recipients. All children <18 years of age who were listed for a heart transplant between 1999 and 2006 were included. Among 3098 children, the median age was 2 years (interquartile range 0.3 to 12 years), and median weight was 12.3 kg (interquartile range 5 to 38 kg); 1294 (42%) were nonwhite; and 1874 (60%) were listed as status 1A (of whom 30% were ventilated and 18% were on extracorporeal membrane oxygenation). Overall, 533 (17%) died, 1943 (63%) received transplants, and 252 (8%) recovered; 370 (12%) remained listed. Multivariate predictors of waiting list mortality include extracorporeal membrane oxygenation support (hazard ratio [HR] 3.1, 95% confidence interval [CI] 2.4 to 3.9), ventilator support (HR 1.9, 95% CI 1.6 to 2.4), listing status 1A (HR 2.2, 95% CI 1.7 to 2.7), congenital heart disease (HR 2.2, 95% CI 1.8 to 2.6), dialysis support (HR 1.9, 95% CI 1.2 to 3.0), and nonwhite race/ethnicity (HR 1.7, 95% CI 1.4 to 2.0). CONCLUSIONS: US waiting list mortality for pediatric heart transplantation remains unacceptably high in the current era. Specific high-risk subgroups can be identified that may benefit from emerging pediatric cardiac assist technologies. The current pediatric heart-allocation system captures medical urgency poorly. Further research is needed to define the optimal organ-allocation system for pediatric heart transplantation.

Hyponatremia among runners in the Boston Marathon.

BACKGROUND: Hyponatremia has emerged as an important cause of race-related death and life-threatening illness among marathon runners. We studied a cohort of marathon runners to estimate the incidence of hyponatremia and to identify the principal risk factors. METHODS: Participants in the 2002 Boston Marathon were recruited one or two days before the race. Subjects completed a survey describing demographic information and training history. After the race, runners provided a blood sample and completed a questionnaire detailing their fluid consumption and urine output during the race. Prerace and postrace weights were recorded. Multivariate regression analyses were performed to identify risk factors associated with hyponatremia. RESULTS: Of 766 runners enrolled, 488 runners (64 percent) provided a usable blood sample at the finish line. Thirteen percent had hyponatremia (a serum sodium concentration of 135 mmol per liter or less); 0.6 percent had critical hyponatremia (120 mmol per liter or less). On univariate analyses, hyponatremia was associated with substantial weight gain, consumption of more than 3 liters of fluids during the race, consumption of fluids every mile, a racing time of >4:00 hours, female sex, and low body-mass index. On multivariate analysis, hyponatremia was associated with weight gain (odds ratio, 4.2; 95 percent confidence interval, 2.2 to 8.2), a racing time of >4:00 hours (odds ratio for the comparison with a time of <3:30 hours, 7.4; 95 percent confidence interval, 2.9 to 23.1), and body-mass-index extremes. CONCLUSIONS: Hyponatremia occurs in a substantial fraction of nonelite marathon runners and can be severe. Considerable weight gain while running, a long racing time, and body-mass-index extremes were associated with hyponatremia, whereas female sex, composition of fluids ingested, and use of nonsteroidal antiinflammatory drugs were not.

Cardiac troponin increases among runners in the Boston Marathon.

STUDY OBJECTIVE: Studies indicate that running a marathon can be associated with increases in serum cardiac troponin levels. The clinical significance of such increases remains unclear. We seek to determine the prevalence of troponin increases and epidemiologic factors associated with these increases in a large and heterogeneous cohort of marathon finishers. METHODS: Entrants in the 2002 Boston Marathon were recruited 1 to 2 days before the race. Data collected included demographic and training history, symptoms experienced during the run, and postrace troponin T and I levels. Simple descriptive statistics were performed to describe the prevalence of troponin increases and runner characteristics. RESULTS: Of 766 runners enrolled, 482 had blood analyzed at the finish line. In all, 34% were women, 20% were younger than 30 years, and 92% had run at least 1 previous marathon. Most runners (68%) had some degree of postrace troponin increase (troponin T > or = 0.01 ng/mL or troponin I > or = 0.1 ng/mL), and 55 (11%) had significant increases (troponin T > or = 0.075 ng/mL or troponin I > or = 0.5 ng/mL). Running inexperience (< 5 previous marathons) and young age (< 30 years) were associated with elevated troponins. These correlates were robust throughout a wide range of troponin thresholds considered. Health factors, family history, training, race performance, and symptoms were not associated with increases. CONCLUSION: Troponin increases were relatively common among marathon finishers and can reach levels typically diagnostic for acute myocardial infarction. Less marathon experience and younger age appeared to be associated with troponin increases, whereas race duration and the presence of traditional cardiovascular risk factors were not. Further work is needed to determine the clinical significance of these findings.

Current management of severe congenital mitral stenosis: outcomes of transcatheter and surgical therapy in 108 infants and children.

BACKGROUND: Severe congenital mitral stenosis (MS) is a rare anomaly that is frequently associated with additional left heart obstructions. Anatomic treatments for congenital MS include balloon mitral valvuloplasty (BMVP), surgical mitral valvuloplasty (SMVP), and mitral valve replacement (MVR), although the optimal therapeutic strategy is unclear. METHODS AND RESULTS: Between 1985 and 2003, 108 patients with severe congenital MS underwent BMVP or surgical intervention at a median age of 18 months (range 1 month to 17.9 years). Anatomic subtypes of MS were "typical" congenital MS in 78 patients, supravalvar mitral ring in 46, parachute mitral valve in 28, and double-orifice mitral valve in 11, with multiple types in approximately 50% of patients. Additional left heart anomalies were present in 82 patients (76%). The first MS intervention was BMVP in 64 patients, SMVP in 33, and MVR in 11. BMVP decreased peak and mean MS gradients by a median of 33% and 38%, respectively (P<0.001), but was complicated by significant mitral regurgitation in 28%. Cross-sectional follow-up was obtained at 4.8+/-4.2 years. Overall, Kaplan-Meier survival was 92% at 1 month, 84% at 1 year, and 77% at 5 years, with 69% 5-year survival during the first decade of our experience and 87% since (P=0.09). Initial MVR and younger age were associated with worse survival. Survival free from failure of biventricular repair or mitral valve reintervention was 55% at 1 year among patients who underwent BMVP and 69% among patients who underwent supravalvar mitral ring resection initially. Among patients who underwent BMVP, survival free from failure of biventricular repair or MVR was 79% at 1 month and 55% at 5 years, with worse outcome in younger patients and those who developed significant postdilation mitral regurgitation. CONCLUSIONS: BMVP effectively relieves left ventricular inflow obstruction in most infants and children with severe congenital MS who require intervention. However, surgical resection is preferable in patients with MS due to a supravalvar mitral ring. Five-year survival is relatively poor in patients with severe congenital MS, with worse outcomes in infants and patients undergoing MVR, but has improved in our more recent experience. Many patients have undergone second procedures for either recurrent/residual MS or mitral regurgitation resulting from dilation-related disruption of the mitral valve apparatus.

Impact of ventricular assist device placement on longitudinal renal function in children with end-stage heart failure.

BACKGROUND: Although ventricular assist devices (VADs) restore hemodynamics in those with heart failure, reversibility of end-organ dysfunction with VAD support is not well characterized. Renal function often improves in adults after VAD placement, but this has not been comprehensively explored in children. METHODS: Sixty-three children on VAD support were studied. Acute kidney injury (AKI) was defined by Kidney Disease: Improving Global Outcomes criteria. Estimated glomerular filtration rate (eGFR) was determined by the Schwartz method. Generalized linear mixed-effects models compared the pre-VAD and post-VAD eGFR for the cohort and sub-groups with and without pre-VAD renal dysfunction (pre-VAD eGFR < 90 ml/min/1.73 m(2)). RESULTS: The pre-VAD eGFR across the cohort was 84.0 ml/min/1.73 m(2) (interquartile range [IQR] 62.3-122.7), and 55.6% (34 of 63) had pre-VAD renal dysfunction. AKI affected 60.3% (38 of 63), with similar rates in those with and without pre-existing renal dysfunction. Within the cohort, the nadir eGFR occurred 1 day post-operatively (62.9 ml/min/1.73 m(2); IQR, 51.2-88.9 ml/min/1.73 m(2); p < 0.001). By Day 5, however, the eGFR exceeded the baseline (99.0 ml/min/1.73 m(2); IQR, 59.3-146.7 ml/min/1.73 m(2); p = 0.03) and remained significantly higher through the first post-operative week. After adjusting for age, gender, and AKI, the eGFR continued to increase throughout the entire 180-day study period (ß = 0.0025; 95% confidence interval, 0.0015-0.0036; p < 0.001). Patients with pre-VAD renal dysfunction experienced the greatest improvement in the eGFR (ß = 0.0051 vs ß = 0.0013, p < 0.001). CONCLUSIONS: Renal dysfunction is prevalent in children with heart failure undergoing VAD placement. Although peri-operative AKI is common, renal function improves substantially in the first post-operative week and for months thereafter. This is particularly pronounced in those with pre-VAD renal impairment, suggesting that VADs may facilitate recovery and maintenance of kidney function in children with advanced heart failure.

Pediatric heart failure and worsening renal function: association with outcomes after heart transplantation.

BACKGROUND: Renal function deteriorates in some children awaiting heart transplantation. This study was initiated to assess the effects of worsening renal function (WRF) on post-heart transplantation outcomes and to determine the effect of waiting-list associated WRF on survival after heart transplantation. METHODS: All children aged <18 years who underwent their first heart transplantation between 1999 and 2009, had reported plasma creatinine concentrations at listing and at transplantation, and were free of renal replacement therapy at listing were identified using the Organ Procurement and Transplant Network database. The independent effects of WRF on in-hospital mortality and post-discharge survival were assessed using logistic regression and log-rank analyses, respectively. RESULTS: Of the 2,216 children included in the analysis, WRF occurred in 334 (15%) awaiting heart transplantation: WRF was mild (stage 1) in 210 (63%), moderate (stage 2) in 40 (12%), and severe (stage 3) in 84 (25%). All WRF stages were independently associated with in-hospital, post-transplant mortality: mild WRF with adjusted odds ratio (AOR) of 2.1 (95% confidence interval [CI], 1.2-3.5); moderate WRF, 2.7 (95% CI, 1.1-6.7); and severe WRF, 3.6 (95% CI, 2.0-6.5). WRF was not associated with death after discharge (hazard ratio, 1.2; 95% CI, 0.9-1.7) at a median follow-up of 2.7 years. CONCLUSIONS: WRF occurs in 15% of children awaiting heart transplantation and is associated with early but not late post-transplant mortality.

Bridging children of all sizes to cardiac transplantation: the initial multicenter North American experience with the Berlin Heart EXCOR ventricular assist device.

BACKGROUND: Beginning in 2000 and accelerating in 2004, the Berlin Heart EXCOR (Berlin Heart Inc Woodlands, TX) became the first pediatric-specific ventricular assist device (VAD) applied throughout North America for children of all sizes. This retrospective study analyzed the initial Berlin Heart EXCOR pediatric experience as a bridge to transplantation. METHODS: Between June 2000 and May 2007, 97 EXCOR VADs were implanted in North America at 29 different institutions. The analysis is limited to 73 patients (75%) from 17 institutions, for which retrospective data were available. RESULTS: Median age and weight at VAD implant were 2.1 years (range, 12 days-17.8 years) and 11 kg (range, 3-87.6 kg), respectively. The primary diagnoses were dilated cardiomyopathy in 42 (58%), congenital heart disease in 19 (26%), myocarditis in 7 (10%), and other cardiomyopathies in 5 (7%). Pre-implant clinical condition was critical cardiogenic shock in 38 (52%), progressive decline in 33 (45%), or other in 2 (3%). Extracorporeal membrane oxygenation was used as a bridge to EXCOR in 22 patients (30%). Device selection was left VAD (LVAD) in 42 (57%) and biventricular assist devices (BiVAD) in 31 (43%). The EXCOR bridged 51 patients (70%) to transplant and 5 (7%) to recovery. Mortality on the EXCOR was 23% (n = 17) overall, including 35% (11 of 31) in BiVAD vs 14% (6 of 42) in LVAD patients (p = 0.003). Multivariate analysis showed younger age and BiVAD support were significant risk factors for death while on the EXCOR. CONCLUSIONS: This limited but large preliminary North American experience with the Berlin Heart EXCOR VAD as a bridge to cardiac transplantation for children of all ages and sizes points to the feasibility of this approach. The prospective investigational device evaluation trial presently underway will further characterize the safety and efficacy of the EXCOR as a bridge to pediatric cardiac transplantation.

Incidence and risk factors for mortality in infants awaiting heart transplantation in the USA.

BACKGROUND: Infants awaiting heart transplantation (HT) face the highest wait-list mortality among all children and adults listed for HT in the USA. We sought to determine the risk of death for infants <12 months old while awaiting HT in the current era, and to identify the principle risk factors associated with wait-list mortality. METHODS: We analyzed outcomes for all infants listed for HT in the USA from January 1999 to July 2006, using data reported to the U.S. Scientific Registry of Transplant Recipients. RESULTS: Of the 1,133 listed infants, 61% were <3 months of age, 80% were listed as Status 1A, 64% had a congenital heart disease (CHD) and 31% had cardiomyopathy. Of 724 infants with CHD, 25% were on prostaglandin (PG) and 27% had a history of prior surgery. By 6 months after listing, 23% died on the wait-list and 54% were transplanted. Multivariate factors associated with wait-list mortality were weight <3 kg (hazard ratio [HR] 1.4, 95% confidence interval [CI] 1.0 to 1.9), extracorporeal membrane oxygenation (ECMO) support (HR 5.6, CI 4.0 to 7.9), ventilator support (HR 2.1, 95% CI 1.6 to 2.8), CHD with PG support (HR 2.8, 95% CI 1.8 to 4.3), CHD without prior surgery (HR 2.8, 95% CI 1.9 to 3.9) and non-white race/ethnicity (HR 1.8, 95% CI 1.4 to 2.3). CONCLUSIONS: One in four infants listed for HT in the USA die before a donor heart can be identified. Wait-list mortality is associated with weight <3 kg, level of invasive support and CHD, but not listing status, which captures medical urgency poorly. Measures to expand infant organ donation, especially among neonates, are urgently needed.

Outcome after Fontan failure and takedown to an intermediate palliative circulation.

BACKGROUND: Fontan takedown to an intermediate palliative circulation is an important treatment option for patients with acute or subacute failure of a Fontan circulation from a variety of causes. Little is known about the subsequent outcome of these patients or their potential candidacy for a second attempt at Fontan completion. METHODS: Patients followed up at Children's Hospital Boston who underwent takedown of a Fontan circulation to an intermediate palliative circulation within 1 year of Fontan completion were reviewed. RESULTS: Between 1979 and 2006, 53 patients underwent Fontan takedown at a median age of 2.3 years (range, 0.3 to 36.5 years). Takedown was performed during the Fontan procedure itself in 12 patients (22%), within the first postoperative month in 31(58%), and between 1 month and 1 year in 10 (18%). Overall, 29 patients (55%) survived the early period after takedown, and 19 ultimately underwent successful Fontan completion a median of 4.6 years after takedown; all but one was alive a median of 6.4 years later. Thirteen (68%) of the 19 had treatable abnormalities contributing to Fontan failure. CONCLUSIONS: Fontan takedown can provide effective stabilization of the acutely or subacutely failing Fontan circulation, although a substantial number of patients die early despite Fontan takedown. Subjects surviving the perioperative period can often undergo uneventful redo Fontan. A thorough evaluation for treatable abnormalities should be performed in all patients with a failing Fontan circulation and in patients who undergo Fontan takedown.

High-risk medical devices, children and the FDA: regulatory challenges facing pediatric mechanical circulatory support devices.

Pediatric mechanical circulatory support is a critical unmet need in the United States. Infant- and child-sized ventricular assist devices are currently being developed largely through federal contracts and grants through the National Heart, Lung, and Blood Institute (NHLBI). Human testing and marketing of high-risk devices for children raises epidemiologic and regulatory issues that will need to be addressed. Leaders from the US Food and Drug Administration (FDA), NHLBI, academic pediatric community, and industry convened in January 2006 for the first FDA Workshop on the Regulatory Process for Pediatric Mechanical Circulatory Support Devices. The purpose was to provide the pediatric community with an overview of the federal regulatory process for high-risk medical devices and to review the challenges specific to the development and regulation of pediatric mechanical circulatory support devices. Pediatric mechanical circulatory support present significant epidemiologic, logistic, and financial challenges to industry, federal regulators, and the pediatric community. Early interactions with the FDA, shared appreciation of challenges, and careful planning will be critical to avoid unnecessary delays in making potentially life-saving devices available for children. Collaborative efforts to address these challenges are warranted.

Successful use of bivalirudin for cardiac transplantation in a child with heparin-induced thrombocytopenia.

Bivalirudin, a direct thrombin inhibitor, has recently emerged as a promising option for anti-coagulation during cardiopulmonary bypass in patients who cannot receive heparin. There is limited experience with the use of bivalirudin in children. We present the case of a child with heparin-induced thrombocytopenia with thrombosis (HIT Type II) who underwent successful orthotopic cardiac transplantation using bivalirudin as the primary anti-coagulant for cardiopulmonary bypass.

The Boston Marathon Study: a novel approach to research during residency.

Resident physicians from a pediatric academic training program developed a hospital-wide research project in an effort to enhance their residency research experience. In this model, residents themselves assumed primary responsibility for each stage of a large prospective clinical research study. The project, which was integrated successfully into the residency program, enabled a large group of residents, with mentorship from a dedicated faculty member, to benefit from a structured clinical research experience while providing the flexibility necessary to meet the demands of a busy residency curriculum. Careful topic selection with a well-defined end point, faculty involvement, resident collegiality, and institutional support were factors identified by study leaders as central to the success of this model.