Limited Relationship Between Echocardiographic Measures and Electrocardiographic Markers of Left Ventricular Size in Healthy Children.

Pediatric ECG standards have been defined without echocardiographic confirmation of normal anatomy. The Pediatric Heart Network Normal Echocardiogram Z-score Project provides a racially diverse group of healthy children with normal echocardiograms. We hypothesized that ECG and echocardiographic measures of left ventricular (LV) dimensions are sufficiently correlated in healthy children to imply a clinically meaningful relationship. This was a secondary analysis of a previously described cohort including 2170 digital ECGs. The relationship between 6 ECG measures associated with LV size were analyzed with LV Mass (LVMass-z) and left ventricular end-diastolic volume (LVEDV-z) along with 11 additional parameters. Pearson or Spearman correlations were calculated for the 78 ECG-echocardiographic pairs with regression analyses assessing the variance in ECG measures explained by variation in LV dimensions and demographic variables. ECG/echocardiographic measurement correlations were significant and concordant in 41/78 (53%), though many were significant and discordant (13/78). Of the 6 ECG parameters, 5 correlated in the clinically predicted direction for LV Mass-z and LVEDV-z. Even when statistically significant, correlations were weak (0.05-0.24). R2 was higher for demographic variables than for echocardiographic measures or body surface area in all pairs, but remained weak (R2 ≤ 0.17). In a large cohort of healthy children, there was a positive association between echocardiographic measures of LV size and ECG measures of LVH. These correlations were weak and dependent on factors other than echocardiographic or patient derived variables. Thus, our data support deemphasizing the use of solitary, traditional measurement-based ECG markers traditionally thought to be characteristic of LVH as standalone indications for further cardiac evaluation of LVH in children and adolescents.

Genetic and clinical variables act synergistically to impact neurodevelopmental outcomes in children with single ventricle heart disease.

BACKGROUND: Recent large-scale sequencing efforts have shed light on the genetic contribution to the etiology of congenital heart defects (CHD); however, the relative impact of genetics on clinical outcomes remains less understood. Outcomes analyses using genetics are complicated by the intrinsic severity of the CHD lesion and interactions with conditionally dependent clinical variables. METHODS: Bayesian Networks were applied to describe the intertwined relationships between clinical variables, demography, and genetics in a cohort of children with single ventricle CHD. RESULTS: As isolated variables, a damaging genetic variant in a gene related to abnormal heart morphology and prolonged ventilator support following stage I palliative surgery increase the probability of having a low Mental Developmental Index (MDI) score at 14 months of age by 1.9- and 5.8-fold, respectively. However, in combination, these variables act synergistically to further increase the probability of a low MDI score by 10-fold. The absence of a damaging variant in a known syndromic CHD gene and a shorter post-operative ventilator support increase the probability of a normal MDI score 1.7- and 2.4-fold, respectively, but in combination increase the probability of a good outcome by 59-fold. CONCLUSIONS: Our analyses suggest a modest genetic contribution to neurodevelopmental outcomes as isolated variables, similar to known clinical predictors. By contrast, genetic, demographic, and clinical variables interact synergistically to markedly impact clinical outcomes. These findings underscore the importance of capturing and quantifying the impact of damaging genomic variants in the context of multiple, conditionally dependent variables, such as pre- and post-operative factors, and demography.

Single ventricle congenital heart disease is a birth defect. In these children, the heart has only one effective blood-pumping chamber instead of two. Surgery can reroute the blood to use only one chamber, but multiple risk factors influence how well a child develops afterwards. Studying these risk factors can be challenging because they are interconnected, i.e. children with a genetic birth defect may be more likely to have a lower birthweight, and hence more likely to spend longer in hospital after surgery. Here, we used a statistical approach not commonly applied to study congenital heart disease and describe that whether a genetic variant (a small difference in a child's DNA) is important for how a child with single ventricle heart disease develops and grows after surgery depends on the presence of other risk factors.

Contribution of Previously Unrecognized RNA Splice-Altering Variants to Congenital Heart Disease.

BACKGROUND: Known genetic causes of congenital heart disease (CHD) explain <40% of CHD cases, and interpreting the clinical significance of variants with uncertain functional impact remains challenging. We aim to improve diagnostic classification of variants in patients with CHD by assessing the impact of noncanonical splice region variants on RNA splicing. METHODS: We tested de novo variants from trio studies of 2649 CHD probands and their parents, as well as rare (allele frequency, <2×10-6) variants from 4472 CHD probands in the Pediatric Cardiac Genetics Consortium through a combined computational and in vitro approach. RESULTS: We identified 53 de novo and 74 rare variants in CHD cases that alter splicing and thus are loss of function. Of these, 77 variants are in known dominant, recessive, and candidate CHD genes, including KMT2D and RBFOX2. In 1 case, we confirmed the variant's predicted impact on RNA splicing in RNA transcripts from the proband's cardiac tissue. Two probands were found to have 2 loss-of-function variants for recessive CHD genes HECTD1 and DYNC2H1. In addition, SpliceAI-a predictive algorithm for altered RNA splicing-has a positive predictive value of ≈93% in our cohort. CONCLUSIONS: Through assessment of RNA splicing, we identified a new loss-of-function variant within a CHD gene in 78 probands, of whom 69 (1.5%; n=4472) did not have a previously established genetic explanation for CHD. Identification of splice-altering variants improves diagnostic classification and genetic diagnoses for CHD. REGISTRATION: URL: https://clinicaltrials.gov; Unique identifier: NCT01196182.

Neither cardiac mitochondrial DNA variation nor copy number contribute to congenital heart disease risk.

The well-established manifestation of mitochondrial mutations in functional cardiac disease (e.g., mitochondrial cardiomyopathy) prompted the hypothesis that mitochondrial DNA (mtDNA) sequence and/or copy number (mtDNAcn) variation contribute to cardiac defects in congenital heart disease (CHD). MtDNAcns were calculated and rare, non-synonymous mtDNA mutations were identified in 1,837 CHD-affected proband-parent trios, 116 CHD-affected singletons, and 114 paired cardiovascular tissue/blood samples. The variant allele fraction (VAF) of heteroplasmic variants in mitochondrial RNA from 257 CHD cardiovascular tissue samples was also calculated. On average, mtDNA from blood had 0.14 rare variants and 52.9 mtDNA copies per nuclear genome per proband. No variation with parental age at proband birth or CHD-affected proband age was seen. mtDNAcns in valve/vessel tissue (320 ± 70) were lower than in atrial tissue (1,080 ± 320, p = 6.8E-21), which were lower than in ventricle tissue (1,340 ± 280, p = 1.4E-4). The frequency of rare variants in CHD-affected individual DNA was indistinguishable from the frequency in an unaffected cohort, and proband mtDNAcns did not vary from those of CHD cohort parents. In both the CHD and the comparison cohorts, mtDNAcns were significantly correlated between mother-child, father-child, and mother-father. mtDNAcns among people with European (mean = 52.0), African (53.0), and Asian haplogroups (53.5) were calculated and were significantly different for European and Asian haplogroups (p = 2.6E-3). Variant heteroplasmic fraction (HF) in blood correlated well with paired cardiovascular tissue HF (r = 0.975) and RNA VAF (r = 0.953), which suggests blood HF is a reasonable proxy for HF in heart tissue. We conclude that mtDNA mutations and mtDNAcns are unlikely to contribute significantly to CHD risk.

Streamlining statistical reproducibility: NHLBI ORCHID clinical trial results reproduction.

Reproducibility in medical research has been a long-standing issue. More recently, the COVID-19 pandemic has publicly underlined this fact as the retraction of several studies reached out to general media audiences. A significant number of these retractions occurred after in-depth scrutiny of the methodology and results by the scientific community. Consequently, these retractions have undermined confidence in the peer-review process, which is not considered sufficiently reliable to generate trust in the published results. This partly stems from opacity in published results, the practical implementation of the statistical analysis often remaining undisclosed. We present a workflow that uses a combination of informatics tools to foster statistical reproducibility: an open-source programming language, Jupyter Notebook, cloud-based data repository, and an application programming interface can streamline an analysis and help to kick-start new analyses. We illustrate this principle by (1) reproducing the results of the ORCHID clinical trial, which evaluated the efficacy of hydroxychloroquine in COVID-19 patients, and (2) expanding on the analyses conducted in the original trial by investigating the association of premedication with biological laboratory results. Such workflows will be encouraged for future publications from National Heart, Lung, and Blood Institute-funded studies.

Effects of blood pressure percentile, body mass index, and race on left ventricular mass in children.

OBJECTIVE: To evaluate the association of systolic blood pressure percentile, race, and body mass index with left ventricular hypertrophy on electrocardiogram and echocardiogram to define populations at risk. STUDY DESIGN: This is a retrospective cross-sectional study design utilising a data analytics tool (Tableau) combining electrocardiogram and echocardiogram databases from 2003 to 2020. Customized queries identified patients aged 2-18 years who had an outpatient electrocardiogram and echocardiogram on the same date with available systolic blood pressure and body measurements. Cases with CHD, cardiomyopathy, or arrhythmia diagnoses were excluded. Echocardiograms with left ventricle mass (indexed to height2.7) were included. The main outcome was left ventricular hypertrophy on echocardiogram defined as Left ventricle mass index greater than the 95th percentile for age. RESULTS: In a cohort of 13,539 patients, 6.7% of studies had left ventricular hypertrophy on echocardiogram. Systolic blood pressure percentile >90% has a sensitivity of 35% and specificity of 82% for left ventricular hypertrophy on echocardiogram. Left ventricular hypertrophy on electrocardiogram was a poor predictor of left ventricular hypertrophy on echocardiogram (9% sensitivity and 92% specificity). African American race (OR 1.31, 95% CI = 1.10, 1.56, p = 0.002), systolic blood pressure percentile >95% (OR = 1.60, 95% CI = 1.34, 1.93, p < 0.001), and higher body mass index (OR = 7.22, 95% CI = 6.23, 8.36, p < 0.001) were independently associated with left ventricular hypertrophy on echocardiogram. CONCLUSIONS: African American race, obesity, and hypertension on outpatient blood pressure measurements are independent risk factors for left ventricular hypertrophy in children. Electrocardiogram has little utility in the screening for left ventricular hypertrophy.

Opportunities and challenges in heart rhythm research: Rationale and development of an electrophysiology collaboratory.

There are many challenges in the current landscape of electrophysiology (EP) clinical and translational research, including increasing costs and complexity, competing demands, regulatory requirements, and challenges with study implementation. This review seeks to broadly discuss the state of EP research, including challenges and opportunities. Included here are results from a Heart Rhythm Society (HRS) Research Committee member survey detailing HRS members' perspectives regarding both barriers to clinical and translational research and opportunities to address these challenges. We also provide stakeholder perspectives on barriers and opportunities for future EP research, including input from representatives of the U.S. Food and Drug Administration, industry, and research funding institutions that participated in a Research Collaboratory Summit convened by HRS. This review further summarizes the experiences of the heart failure and heart valve communities and how they have approached similar challenges in their own fields. We then explore potential solutions, including various models of research ecosystems designed to identify research challenges and to coordinate ways to address them in a collaborative fashion in order to optimize innovation, increase efficiency of evidence generation, and advance the development of new therapeutic products. The objectives of the proposed collaborative cardiac EP research community are to encourage and support scientific discourse, research efficiency, and evidence generation by exploring collaborative and equitable solutions in which stakeholders within the EP community can interact to address knowledge gaps, innovate, and advance new therapies.

Geographical variation in infant mortality due to congenital heart disease in the USA: a population-based cohort study.

BACKGROUND: Little is known about geographical variation in infant mortality due to congenital heart disease (CHD) and the social determinants of health that might mediate such variation. We aimed to examine US county-level estimates of infant mortality due to CHD to understand geographical patterns and factors that might influence variation in mortality. METHODS: This US population-based cohort study used linked livebirth-infant death cohort files from the US National Center for Health Statistics from Jan 1, 2006, to Dec 31, 2015. All deaths attributable to congenital heart disease in infants in a given year were included. We used hierarchical Bayesian models to estimate rates of infant mortality due to congenital heart disease for all US counties. We mapped model-based estimates to explore geographical patterns. Covariates included infant sex, gestational age, maternal race and ethnicity, percentage of the county population below the poverty level, and proximity of the county to a US News & World Report 2015 top-50 ranked paediatric cardiac centre. FINDINGS: From 2006 to 2015, 40 847 089 livebirths occurred, of which there were 13 988 infant deaths attributed to congenital heart disease, with an unadjusted infant mortality rate due to CHD of 0·34 per 1000 livebirths (95% CI 0·34-0·35). Kentucky and Mississippi had the greatest proportions of counties with a predicted rate of infant mortality due to CHD above the 95th percentile. All counties in Connecticut, Massachusetts, and Rhode Island had a predicted rate below the fifth percentile. In the model, lower mortality risk correlated with closer proximity to a top-50 ranked paediatric cardiac centre (odds ratio [OR] 0·890, 95% credible interval [CrI] 0·840-0·942), whereas higher mortality risk correlated with higher levels of poverty (OR 1·181, 95% CrI 1·125-1·239). INTERPRETATION: Substantial geographical variation exists in infant mortality due to CHD in the USA, highlighting the potential importance of bolstering care delivery for infants from economically deprived communities and areas remote from top-performing paediatric cardiac centres. FUNDING: None.

Impact of Major Residual Lesions on Outcomes After Surgery for Congenital Heart Disease.

BACKGROUND: Many factors affect outcomes after congenital cardiac surgery. OBJECTIVES: The RLS (Residual Lesion Score) study explored the impact of severity of residual lesions on post-operative outcomes across operations of varying complexity. METHODS: In a prospective, multicenter, observational study, 17 sites enrolled 1,149 infants undergoing 5 common operations: tetralogy of Fallot repair (n = 250), complete atrioventricular septal defect repair (n = 249), arterial switch operation (n = 251), coarctation or interrupted arch with ventricular septal defect (VSD) repair (n = 150), and Norwood operation (n = 249). The RLS was assigned based on post-operative echocardiography and clinical events: RLS 1 (trivial or no residual lesions), RLS 2 (minor residual lesions), or RLS 3 (reintervention for or major residual lesions before discharge). The primary outcome was days alive and out of hospital within 30 post-operative days (60 for Norwood). Secondary outcomes assessed post-operative course, including major medical events and days in hospital. RESULTS: RLS 3 (vs. RLS 1) was an independent risk factor for fewer days alive and out of hospital (p ≤ 0.008) and longer post-operative hospital stay (p ≤ 0.02) for all 5 operations, and for all secondary outcomes after coarctation or interrupted arch with VSD repair and Norwood (p ≤ 0.03). Outcomes for RLS 1 versus 2 did not differ consistently. RLS alone explained 5% (tetralogy of Fallot repair) to 20% (Norwood) of variation in the primary outcome. CONCLUSIONS: Adjusting for pre-operative factors, residual lesions after congenital cardiac surgery impacted in-hospital outcomes across operative complexity with greatest impact following complex operations. Minor residual lesions had minimal impact. These findings may provide guidance for surgeons when considering short-term risks and benefits of returning to bypass to repair residual lesions.

Exercise Capacity and Predictors of Performance After Fontan: Results from the Pediatric Heart Network Fontan 3 Study.

Impaired exercise following Fontan is a surrogate of morbidity. Single-center longitudinal data exist, but there is a lack of contemporary multi-center data. Ramp cycle ergometry was re-performed in consented participants who had originally participated in the Pediatric Heart Network's Fontan cross-sectional study. Annualized change was evaluated at maximal and submaximal exercise. Associations between these outcomes and patient characteristics were analyzed. There were 336 participants in Fontan 3, mean age 23.2 years. Paired measurements of peak oxygen consumption (peak VO2) were available for 95; peak exercise data at Fontan 3 were available for 275. Percent-predicted peak VO2 declined by 0.8 ± 1.7% per year (p < 0.001). At Fontan 3, the lowest performing peak VO2 tertile had the highest rate of overweight and obesity (p < 0.001). Female gender was more prevalent in the highest performing tertile (p = 0.004). Paired data at the ventilatory anaerobic threshold (VO2 at VAT) were available for 196; VAT data at Fontan 3 were available for 311. Percent-predicted VO2 at VAT decreased by 0.8 ± 2.6% per year (p < 0.001). At Fontan 3, VO2 at VAT was better preserved than peak VO2 across all tertiles, with higher rates of overweight and obesity in the lower performing group (p = 0.001). Female gender (p < 0.001) and left ventricular morphology (p = 0.03) were associated with better performance. Submaximal exercise is better preserved than maximal in the Fontan population, but declined at the same rate over the study period. The overall longitudinal rate of decline in exercise performance is slower than what has been described previously.

Epidemiology of Sudden Death in a Population-Based Study of Infants and Children.

OBJECTIVE: To describe epidemiologic data from the Sudden Death in the Young (SDY) Case Registry. Understanding the scope of SDY may optimize prevention efforts. STUDY DESIGN: We analyzed sudden, unexpected deaths of infants (<365 days) and children (1-17 years) from a population-based registry of 8 states/jurisdictions in 2015 and 9 in 2016. Natural deaths and injury deaths from drowning, motor vehicle accident drivers, and infant suffocation were included; other injury deaths, homicide, suicide, intentional overdose, and terminal illness were excluded. Cases were categorized using a standardized algorithm. Descriptive statistics were used to characterize deaths, and mortality rates were calculated. RESULTS: Of 1319 cases identified, 92% had an autopsy. We removed incomplete cases, leaving 1132 analyzable deaths (889 infants, 243 children). The SDY rate for infants was 120/100 000 live births and for children was 1.9/100 000 children. Explained Cardiac rates were greater for infants (2.7/100 000 live births) than children (0.3/100 000 children). The pediatric Sudden Unexpected Death in Epilepsy (SUDEP) mortality rate was 0.2/100 000 live births and children. Blacks comprised 42% of infant and 43% of child deaths but only 23% of the population. In all ages, myocarditis/endocarditis was the most common Explained Cardiac cause; respiratory illness was the most common Explained Other cause. SDY occurred during activity in 13% of childhood cases. CONCLUSIONS: Prevention strategies include optimizing identification and treatment of respiratory and cardiac diseases.

De Novo Damaging Variants, Clinical Phenotypes, and Post-Operative Outcomes in Congenital Heart Disease.

BACKGROUND: De novo genic and copy number variants are enriched in patients with congenital heart disease, particularly those with extra-cardiac anomalies. The impact of de novo damaging variants on outcomes following cardiac repair is unknown. METHODS: We studied 2517 patients with congenital heart disease who had undergone whole-exome sequencing as part of the CHD GENES study (Congenital Heart Disease Genetic Network). RESULTS: Two hundred ninety-four patients (11.7%) had clinically significant de novo variants. Patients with de novo damaging variants were 2.4 times more likely to have extra-cardiac anomalies (P=5.63×10-12). In 1268 patients (50.4%) who had surgical data available and underwent open-heart surgery exclusive of heart transplantation as their first operation, we analyzed transplant-free survival following the first operation. Median follow-up was 2.65 years. De novo variants were associated with worse transplant-free survival (hazard ratio, 3.51; P=5.33×10-04) and longer times to final extubation (hazard ratio, 0.74; P=0.005). As de novo variants had a significant interaction with extra-cardiac anomalies for transplant-free survival (P=0.003), de novo variants conveyed no additional risk for transplant-free survival for patients with these anomalies (adjusted hazard ratio, 1.96; P=0.06). By contrast, de novo variants in patients without extra-cardiac anomalies were associated with worse transplant-free survival during follow-up (hazard ratio, 11.21; P=1.61×10-05) than that of patients with no de novo variants. Using agnostic machine-learning algorithms, we identified de novo copy number variants at 15q25.2 and 15q11.2 as being associated with worse transplant-free survival and 15q25.2, 22q11.21, and 3p25.2 as being associated with prolonged time to final extubation. CONCLUSIONS: In patients with congenital heart disease undergoing open-heart surgery, de novo variants were associated with worse transplant-free survival and longer times on the ventilator. De novo variants were most strongly associated with adverse outcomes among patients without extra-cardiac anomalies, suggesting a benefit for preoperative genetic testing even when genetic abnormalities are not suspected during routine clinical practice. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01196182.

Registry-based trials: a potential model for cost savings?

BACKGROUND/AIMS: Registry-based trials have emerged as a potentially cost-saving study methodology. Early estimates of cost savings, however, conflated the benefits associated with registry utilisation and those associated with other aspects of pragmatic trial designs, which might not all be as broadly applicable. In this study, we sought to build a practical tool that investigators could use across disciplines to estimate the ranges of potential cost differences associated with implementing registry-based trials versus standard clinical trials. METHODS: We built simulation Markov models to compare unique costs associated with data acquisition, cleaning, and linkage under a registry-based trial design versus a standard clinical trial. We conducted one-way, two-way, and probabilistic sensitivity analyses, varying study characteristics over broad ranges, to determine thresholds at which investigators might optimally select each trial design. RESULTS: Registry-based trials were more cost effective than standard clinical trials 98.6% of the time. Data-related cost savings ranged from $4300 to $600,000 with variation in study characteristics. Cost differences were most reactive to the number of patients in a study, the number of data elements per patient available in a registry, and the speed with which research coordinators could manually abstract data. Registry incorporation resulted in cost savings when as few as 3768 independent data elements were available and when manual data abstraction took as little as 3.4 seconds per data field. CONCLUSIONS: Registries offer important resources for investigators. When available, their broad incorporation may help the scientific community reduce the costs of clinical investigation. We offer here a practical tool for investigators to assess potential costs savings.

Genomic analyses implicate noncoding de novo variants in congenital heart disease.

A genetic etiology is identified for one-third of patients with congenital heart disease (CHD), with 8% of cases attributable to coding de novo variants (DNVs). To assess the contribution of noncoding DNVs to CHD, we compared genome sequences from 749 CHD probands and their parents with those from 1,611 unaffected trios. Neural network prediction of noncoding DNV transcriptional impact identified a burden of DNVs in individuals with CHD (n = 2,238 DNVs) compared to controls (n = 4,177; P = 8.7 × 10-4). Independent analyses of enhancers showed an excess of DNVs in associated genes (27 genes versus 3.7 expected, P = 1 × 10-5). We observed significant overlap between these transcription-based approaches (odds ratio (OR) = 2.5, 95% confidence interval (CI) 1.1-5.0, P = 5.4 × 10-3). CHD DNVs altered transcription levels in 5 of 31 enhancers assayed. Finally, we observed a DNV burden in RNA-binding-protein regulatory sites (OR = 1.13, 95% CI 1.1-1.2, P = 8.8 × 10-5). Our findings demonstrate an enrichment of potentially disruptive regulatory noncoding DNVs in a fraction of CHD at least as high as that observed for damaging coding DNVs.

Enhancing efficiency and scientific impact of a clinical trials network: the Pediatric Heart Network Integrated CARdiac Data and Outcomes (iCARD) Collaborative.

Recent years have seen an exponential increase in the variety of healthcare data captured across numerous sources. However, mechanisms to leverage these data sources to support scientific investigation have remained limited. In 2013 the Pediatric Heart Network (PHN), funded by the National Heart, Lung, and Blood Institute, developed the Integrated CARdiac Data and Outcomes (iCARD) Collaborative with the goals of leveraging available data sources to aid in efficiently planning and conducting PHN studies; supporting integration of PHN data with other sources to foster novel research otherwise not possible; and mentoring young investigators in these areas. This review describes lessons learned through the development of iCARD, initial efforts and scientific output, challenges, and future directions. This information can aid in the use and optimisation of data integration methodologies across other research networks and organisations.

Performance and predictors of recruitment success in National Heart, Lung, and Blood Institute's cardiovascular clinical trials.

Background/Aims Identifying predictors of recruitment success in clinical trials, particularly prior to study launch, could contribute to higher study completion rates and improved scientific return on investment. This article evaluates the performance of clinical trials funded by the National Heart, Lung, and Blood Institute that began recruitment before and after implementation of National Heart, Lung, and Blood Institute's 2009 Accrual Policy and identifies study-related factors that predict recruitment success. Methods A retrospective analysis of National Heart, Lung, and Blood Institute's cardiovascular clinical trials with initial funding from 1996 to 2012 was performed to assess recruitment success. Success was defined as ≥100% enrollment of the proposed sample size within the duration initially proposed by investigators. Trials were assigned to categories (pre-policy vs post-policy) based on whether the first patient was enrolled before or after the 2009 Accrual Policy implementation. Potential determinants of successful recruitment were evaluated using multivariable logistic regression. Results Of 167 trials analyzed, 26.3% met the definition of success. Twenty-four trials (14.4%) were terminated early and 15 (62.5%) for insufficient recruitment. Trials failed due to <100% enrollment (22.8%), longer duration (19.8%), or both (31.1%). Trials testing behavioral interventions, those conducted within a National Heart, Lung, and Blood Institute-funded network, and those with normal controls were predictive of success. The proportion of successful clinical trials increased from 23% in the pre-policy era to 30% post-policy, although the difference was not statistically significant ( p = 0.29). Conclusion Enrollment success rates for National Heart, Lung, and Blood Institute's clinical trials are concerning. The 2009 National Heart, Lung, and Blood Institute Accrual Policy did not significantly improve trial success. Clinical trials testing behavioral interventions, those conducted within networks, and those with normal controls were predictive of recruitment success. Components of networks may provide model practices to help other trials attain success, including close attention to oversight activities such as recruitment plans, real-time enrollment monitoring, corrective action plans to address shortfalls, and close sponsor-investigator collaborations.

Electrocardiograms in Healthy North American Children in the Digital Age.

BACKGROUND: Interpretation of pediatric ECGs is limited by lack of accurate sex- and race-specific normal reference values obtained with modern technology for all ages. We sought to obtain contemporary digital ECG measurements in healthy children from North America, to evaluate the effects of sex and race, and to compare our results to commonly used published datasets. METHODS: Digital ECGs (12-lead) were retrospectively collected for children ≤18 years old with normal echocardiograms at 19 centers in the Pediatric Heart Network. Patients were classified into 36 groups: 6 age, 2 sex, and 3 race (white, black, and other/mixed) categories. Standard intervals and amplitudes were measured; mean±SD and 2nd/98th percentiles were determined by age group, sex, and race. For each parameter, multivariable analysis, stratified by age, was conducted using sex and race as predictors. Parameters were compared with 2 large pediatric ECG data sets. RESULTS: Among ECGs from 2400 children, significant differences were found by sex and race categories. The corrected QT interval in lead II was greater for girls compared with boys for age groups ≥3 years (P≤0.03) and for whites compared with blacks for age groups ≥12 years (P<0.05). The R wave amplitude in V6 was greater for boys compared with girls for age groups ≥12 years (P<0.001), for blacks compared with white or other race categories for age groups ≥3 years (P≤0.006), and greater compared with a commonly used public data set for age groups ≥12 years (P<0.0001). CONCLUSIONS: In this large, diverse cohort of healthy children, most ECG intervals and amplitudes varied by sex and race. These differences have important implications for interpreting pediatric ECGs in the modern era when used for diagnosis or screening, including thresholds for left ventricular hypertrophy.