A risk-prediction model for in-hospital mortality after heart transplantation in US children.

We sought to develop and validate a quantitative risk-prediction model for predicting the risk of posttransplant in-hospital mortality in pediatric heart transplantation (HT). Children <18 years of age who underwent primary HT in the United States during 1999-2008 (n = 2707) were identified using Organ Procurement and Transplant Network data. A risk-prediction model was developed using two-thirds of the cohort (random sample), internally validated in the remaining one-third, and independently validated in a cohort of 338 children transplanted during 2009-2010. The best predictive model had four categorical variables: hemodynamic support (ECMO, ventilator support, VAD support vs. medical therapy), cardiac diagnosis (repaired congenital heart disease [CHD], unrepaired CHD vs. cardiomyopathy), renal dysfunction (severe, mild-moderate vs. normal) and total bilirubin (≥ 2.0, 0.6 to <2.0 vs. <0.6 mg/dL). The C-statistic (0.78) and the Hosmer-Lemeshow goodness-of-fit (p = 0.89) in the model-development cohort were replicated in the internal validation and independent validation cohorts (C-statistic 0.75, 0.81 and the Hosmer-Lemeshow goodness-of-fit p = 0.49, 0.53, respectively) suggesting acceptable prediction for posttransplant in-hospital mortality. We conclude that this risk-prediction model using four factors at the time of transplant has good prediction characteristics for posttransplant in-hospital mortality in children and may be useful to guide decision-making around patient listing for transplant and timing of mechanical support.

Trends in wait-list mortality in children listed for heart transplantation in the United States: era effect across racial/ethnic groups.

We sought to evaluate trends in overall and race-specific pediatric heart transplant (HT) wait-list mortality in the United States (US) during the last 20 years. We identified all children <18 years old listed for primary HT in the US during 1989-2009 (N = 8096, 62% White, 19% Black, 13% Hispanic and 6% Other) using the Organ Procurement and Transplant Network database. Wait-list mortality was assessed in four successive eras (1989-1994, 1995-1999, 2000-2004 and 2005-2009). Overall wait-list mortality declined in successive eras (26%, 23%, 18% and 13%, respectively). The decline across eras remained significant in adjusted analysis (hazard ratio [HR] 0.70 in successive eras, 95% confidence interval [CI], 0.67-0.74) and was 67% lower for children listed during 2005-2009 versus those listed during 1989-1994 (HR 0.33; CI, 0.28-0.39). In models stratified by race, wait-list mortality decreased in all racial groups in successive eras. In models stratified by era, minority children were not at higher risk of wait-list mortality in the most recent era. We conclude that the risk of wait-list mortality among US children listed for HT has decreased by two-thirds during the last 20 years. Racial gaps in wait-list mortality present variably in the past are not present in the current era.

Racial and ethnic differences in mortality in children awaiting heart transplant in the United States.

Racial differences in outcomes are well known in children after heart transplant (HT) but not in children awaiting HT. We assessed racial and ethnic differences in wait-list mortality in children <18 years old listed for primary HT in the United States during 1999-2006 using multivariable Cox models. Of 3299 listed children, 58% were listed as white, 20% as black, 16% as Hispanic, 3% as Asian and 3% were defined as 'Other'. Mortality on the wait-list was 14%, 19%, 21%, 17% and 27% for white, black, Hispanic, Asian and Other children, respectively. Black (hazard ratio [HR] 1.6, 95% confidence interval [CI] 1.3, 1.9), Hispanic (HR 1.5, CI 1.2, 1.9), Asian (HR, 2.0, CI 1.3, 3.3) and Other children (HR 2.3, CI 1.5, 3.4) were all at higher risk of wait-list death compared to white children after controlling for age, listing status, cardiac diagnosis, hemodyamic support, renal function and blood group. After adjusting additionally for medical insurance and area household income, the risk remained higher for all minorities. We conclude that minority children listed for HT have significantly higher wait-list mortality compared to white children. Socioeconomic variables appear to explain a small fraction of this increased risk.

Effect of an acid mine drainage effluent on phytoplankton biomass and primary production at Britannia Beach, Howe Sound, British Columbia.

We investigated the effect of acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach (Howe Sound, BC, Canada) on primary productivity and chlorophyll a levels in the receiving waters of Howe Sound before, during, and after freshet from the Squamish River. Elevated concentrations of copper (integrated average through the water column >0.050 mgl(-1)) in nearshore waters indicated that under some conditions a small gyre near the mouth of Britannia Creek may have retained the AMD from Britannia Creek and from a 30-m deep water outfall close to shore. Regression and correlation analyses indicated that copper negatively affected primary productivity during April (pre-freshet) and November (post-freshet). Negative effects of copper on primary productivity were not supported statistically for July (freshet), possibly because of additional effects such as turbidity from the Squamish River. Depth-integrated average and surface chlorophyll a were correlated to copper concentrations in April. During this short study we demonstrated that copper concentrations from the AMD discharge can negatively affect both primary productivity and the standing stock of primary producers in Howe Sound.

Regional racial and ethnic differences in mortality for congenital heart surgery in children may reflect unequal access to care.

The objective of this study was to explore racial differences in mortality for congenital heart surgery. We performed a population-based retrospective cohort study using hospital discharge abstract data from four states in 1996. The outcome measure was risk-adjusted in-hospital mortality. Cases of pediatric congenital heart surgery were classified into six risk categories using the Risk Adjustment in Congenital Heart Surgery method. Differences in risk-adjusted in-hospital mortality among racial groups were explored. Analyses stratified by state were used to identify regional differences. Of 5791 cases, 4822 (83%) were assigned to a risk group for analysis. Surgical mortality differed for whites compared to non-whites (3.7 vs 5.1%, p = 0.02). Among non-white groups, unadjusted mortality rates varied: Asian, 5.3%; black, 4.1%; Hispanic 4.9%; other, 7.3%; and missing, 7.6% (p = 0.008). Adjusted mortality also differed by race but was inconsistent across regions, making explanatory factors based solely on biology implausible. For example, compared to whites, blacks had a higher risk of dying in Massachusetts [odds ratio (OR) = 6.39, p = 0.08] but lower in Pennsylvania (OR = 0.41, p = 0.009). Adding insurance type to models did not eliminate racial differences. In risk-adjusted analyses, non-white groups had a higher risk of dying after congenital heart surgery than whites. Inconsistent effects among regions suggest that differential mortality is due to unequal access to care rather than biology.

Risk of death for Medicaid recipients undergoing congenital heart surgery.

The objective of this study was to explore the effect of insurance type on mortality for congenital heart surgery. We performed a population-based retrospective cohort study using hospital discharge abstract data from five states in 1992 and 1996. The outcome measure was risk-adjusted in-hospital mortality. Cases of pediatric congenital heart surgery were identified and placed into six risk categories using the Risk Adjustment in Congenital Heart Surgery method. Multivariate analyses were used to determine the effect of insurance type on risk-adjusted mortality; regional effects were explored. Using standardized mortality ratios, institutions were grouped by outcome; within and between group differences were examined. Of 11,636 cases, 9656 (83%) were placed in a risk group for analysis. In 1996, children with Medicaid had a higher risk of death than those with commercial or managed care in both unadjusted (p = 0.002) and adjusted (p < 0.001) analyses. Overall mortality rates decreased between 1992 and 1996 (p = 0.001). However, improvement was not consistent among insurance groups. Differences were present within and between low, average, and high-mortality hospitals, suggesting that the adverse effect of Medicaid may be due to both differential referral and other differences in care among patients treated at similar institutions. Children with Medicaid insurance have a higher risk of dying after congenital heart surgery than those with commercial and some managed care insurance. Barriers to access go beyond differences in referral patterns.

Whole blood ionized magnesium: age-related differences in normal values and clinical implications of ionized hypomagnesemia in patients undergoing surgery for congenital cardiac disease.

OBJECTIVES: We sought to (1) determine reference values for whole blood ionized magnesium concentrations in newborns, children, and young adults and (2) evaluate the frequency and clinical implications of ionized hypomagnesemia in patients undergoing surgery for congenital heart disease. METHOD: We prospectively measured ionized magnesium concentrations in 299 subjects (113 control subjects and 186 patients undergoing surgery for congenital heart disease). Subjects were categorized by age. In the surgical group blood samples were obtained before bypass, during bypass (cooling and rewarming), after bypass, and during admission to the intensive care unit. Ionized hypomagnesemia was defined as ionized magnesium level 2 standard deviations below the mean of control subjects in the same age group. Patients were analyzed, controlling for cardiopulmonary bypass time. RESULTS: In the control group ionized magnesium concentrations differed by age. Neonates and adults showed lower ionized magnesium concentrations compared with those of other age groups. Infants exhibited the highest ionized magnesium concentration. In the surgical group patients older than 1 month showed a higher proportion of ionized hypomagnesemia compared with that found in neonates at baseline (P <.001), after bypass (P =. 03), and at admission to the intensive care unit (P =.02). Controlling for cardiopulmonary bypass time, patients older than 1 month who were hypomagnesemic during bypass showed longer intubation time (P =.001) and longer intensive care stay (P =.01) and tended to have a higher pediatric severity of illness score on intensive care admission (P =.14) compared with patients without ionized hypomagnesemia. CONCLUSIONS: There are age-related differences in normal ionized magnesium concentrations. Ionized hypomagnesemia is a common and clinically relevant occurrence among patients older than 1 month of age undergoing surgery for congenital heart disease.

Changes in whole blood lactate levels during cardiopulmonary bypass for surgery for congenital cardiac disease: an early indicator of morbidity and mortality.

OBJECTIVE: Our objective was to evaluate the change in lactate level during cardiopulmonary bypass and the possible predictive value in identifying patients at high risk of morbidity and mortality after surgery for congenital cardiac disease. METHODS: We prospectively studied lactate levels in 174 nonconsecutive patients undergoing cardiopulmonary bypass during operations for congenital cardiac disease. Arterial blood samples were taken before cardiopulmonary bypass, during cardiopulmonary bypass (cooling and rewarming), after cardiopulmonary bypass, and during admission to the cardiac intensive care unit. Complicated outcomes were defined as open sternum as a response to cardiopulmonary instability, renal failure, cardiac arrest and resuscitation, extracorporeal membrane oxygenation, and death. RESULTS: The largest increment in lactate level occurred during cardiopulmonary bypass. Lactate levels decreased between the postbypass period and on admission to the intensive care unit. Patients who had circulatory arrest exhibited higher lactate levels at all time points. Nonsurvivors had higher lactate levels at all time points. A change in lactate level of more than 3 mmol/L during cardiopulmonary bypass had the optimal sensitivity (82%) and specificity (80%) for mortality, although the positive predictive value was low. CONCLUSIONS: Hyperlactatemia occurs during cardiopulmonary bypass in patients undergoing operations for congenital cardiac disease and may be an early indicator for postoperative morbidity and mortality.

Repeat balloon dilation of congenital valvar aortic stenosis: immediate results and midterm outcome.

While balloon dilation (BD) has become the initial treatment for congenital valvar aortic stenosis (CVAS) at many institutions, repeat BD for recurrent obstruction has been reported only in a few. Between January 1985 and December 1996, 298 patients (70 neonates) underwent BD, 34 of whom underwent a repeat BD without mortality. A greater proportion of neonates had a repeat BD (26% vs. 8%, P < 0.001). At repeat BD (1 day-7.5 years post initial BD), the mean peak-to-peak gradient was reduced from 67+/-24 to 36+/-16 mm Hg (P < 0.0001). Aortic regurgitation (AR) increased immediately in 26%, being moderate or more in 24%. During a mean follow-up of 5.2 years, there was one surgically related death. Of the 33 survivors, 6 had surgery for residual stenosis and/or AR. Among the remaining 27 patients, 96% were asymptomatic, the peak instantaneous aortic valve Doppler gradient was 50+/-15 mm Hg with AR absent in 8%, mild in 62%, and moderate or more in 31%. In conclusion, repeat BD is effective and without mortality. AR was at least moderate in 24% of patients immediately after a second BD. Repeat BD was more common in patients who underwent the initial BD as neonates.