Shear stress associated with cardiopulmonary bypass induces expression of inflammatory cytokines and necroptosis in monocytes.

Cardiopulmonary bypass (CPB) is required during most cardiac surgeries. CBP drives systemic inflammation and multiorgan dysfunction that is especially severe in neonatal patients. Limited understanding of molecular mechanisms underlying CPB-associated inflammation presents a significant barrier to improve clinical outcomes. To better understand these clinical issues, we performed mRNA sequencing on total circulating leukocytes from neonatal patients undergoing CPB. Our data identify myeloid cells, particularly monocytes, as the major cell type driving transcriptional responses to CPB. Furthermore, IL-8 and TNF-α were inflammatory cytokines robustly upregulated in leukocytes from both patients and piglets exposed to CPB. To delineate the molecular mechanism, we exposed THP-1 human monocytic cells to CPB-like conditions, including artificial surfaces, high shear stress, and cooling/rewarming. Shear stress was found to drive cytokine upregulation via calcium-dependent signaling pathways. We also observed that a subpopulation of THP-1 cells died via TNF-α-mediated necroptosis, which we hypothesize contributes to post-CPB inflammation. Our study identifies a shear stress-modulated molecular mechanism that drives systemic inflammation in pediatric CPB patients. These are also the first data to our knowledge to demonstrate that shear stress causes necroptosis. Finally, we observe that calcium and TNF-α signaling are potentially novel targets to ameliorate post-CPB inflammation.

Improving Wait Time for Patients in a Pediatric Echocardiography Laboratory - a Quality Improvement Project.

BACKGROUND: Prolonged wait times for echocardiograms in the outpatient pediatric cardiology clinic led to patient and provider dissatisfaction at our institution. The aims of this project were to measure our baseline performance with regard to echocardiogram wait time (EWT), to implement a formal quality improvement (QI) program to improve EWT, and to measure the impact of QI on EWT. METHODS: A QI team was formed comprising of cardiologists (A.P., T.S.), sonographer (A.W.), and QI mentor (J.M.). EWT was defined as time in minutes from initiation of the order in the electronic medical record to start of the echocardiogram. Goal EWT was set as ≤ 20 minutes for 90% patients. Flowcharts were created after process observation to identify sources of potential delay contributing to EWT. QI methodology such as driver diagrams were utilized to identify interventions, which were then implemented and studied as Plan-Do-Study-Act cycles. RESULTS: Sequential interventions included early start time, huddles involving clinic and echo laboratory staff, patient tracking system, and repurposing of a clinic room for echo. EWT was tracked for 840 patients. Mean EWT was 22.5 ± 17.5 minutes at baseline and decreased to 15.3 ± 7.8 minutes postintervention (P < 0.001). Postintervention, 81% of the patients waited < 20 minutes for their echo, and 98% patients waited < 30 minutes, compared with baseline numbers of 62% and 76%, respectively (P < 0.001). CONCLUSIONS: We were able to utilize QI methodology to derive interventions and track changes, resulting in quantifiable improvement in EWT in a busy pediatric echo laboratory.

Implementation of a Quality Improvement Bundle Improves Echocardiographic Imaging after Congenital Heart Surgery in Children.

BACKGROUND: Postoperative echocardiography after congenital heart disease surgery is of prognostic importance, but variable image quality is problematic. We implemented a quality improvement bundle comprising of focused imaging protocols, procedural sedation, and sonographer education to improve the rate of optimal imaging (OI). METHODS: Predischarge echocardiograms were evaluated in 116 children (median age, 0.51 years; range, 0.01-5.6 years) from two centers after tetralogy of Fallot repair, arterial switch operation, and bidirectional Glenn and Fontan procedures. OI rates were compared between the centers before and after the implementation of a quality improvement bundle at center 1, with center 2 serving as the comparator. Echocardiographic images were independently scored by a single reader from each center, blinded to center and time period. For each echocardiographic variable, quality score was assigned as 0 (not imaged or suboptimally imaged) or 1 (optimally imaged); structures were classified as intra- or extracardiac. The rate of OI was calculated for each variable as the percentage of patients assigned a score of 1. RESULTS: Intracardiac structures had higher OI than extracardiac structures (81% vs 57%; adjusted odds ratio [OR], 3.47; P < .01). Center 1 improved overall OI from 48% to 73% (OR, 4.44; P < .01), intracardiac OI from 69% to 85% (OR, 3.53; P = .01), and extracardiac OI from 35% to 67% (OR, 5.16; P < .01). There was no temporal difference for center 2. CONCLUSIONS: After congenital heart disease surgery in children, intracardiac structures are imaged more optimally than extracardiac structures. Focused imaging protocols, patient sedation, and sonographer education can improve OI rates.

Impact of Variability in Echocardiographic Interpretation on Assessment of Adequacy of Repair Following Congenital Heart Surgery: A Pilot Study.

Technical Performance Score (TPS) is based largely on the presence and magnitude of residual lesions on postoperative echocardiograms; this score correlates with outcomes following repair of congenital heart defects. We evaluated reader variability for echocardiographic components of TPS for complete repair of tetralogy of Fallot (TOF) and arterial switch operation (ASO) in two centers and measured its effect on TPS. Postoperative echocardiograms were evaluated in 67 children (39 TOF and 28 ASO). Two readers (one per center) interpreted each echocardiogram. Reader variability in image quality assessments and measurements was compared using weighted kappa (κ), percent agreement, and intra-class correlation. TPS class (1 optimal-no residua, 2 adequate-minor residua, 3 inadequate-major residua) was assigned for each echocardiographic review by an independent investigator. The effect of reader interpretation variability on TPS classification was measured. There was strong agreement for TPS between the two readers (κ = 0.88). The readers were concordant for TPS classes for 57 children (85%) and discordant for classes 2 (minor residua) versus 3 (major residua) in six (9%). Coronary arteries and branch pulmonary arteries were frequently suboptimally visualized. Although inter-reader agreement for TPS was strong, inter-reader variation in echocardiographic interpretations had a small, but important effect on TPS for TOF and ASO, particularly for the distinction between minor and major residua. Further studies of generalizability and reproducibility of TPS and refinement of scoring modules may be needed before it can be used as a tool to assess pediatric cardiac surgical performance and outcomes.

MicroRNA-421 Dysregulation is Associated with Tetralogy of Fallot.

The importance of microRNAs for maintaining stability in the developing vertebrate heart has recently become apparent. In addition, there is a growing appreciation for the significance of microRNAs in developmental pathology, including the formation of congenital heart defects. We examined the expression of microRNAs in right ventricular (RV) myocardium from infants with idiopathic tetralogy of Fallot (TOF, without a 22q11.2 deletion), and found 61 microRNAs to be significantly changed in expression in myocardium from children with TOF compared to normally developing comparison subjects (O'Brien et al. 2012). Predicted targets of microRNAs with altered expression were enriched for gene networks that regulate cardiac development. We previously derived a list of 229 genes known to be critical to heart development, and found 44 had significantly changed expression in TOF myocardium relative to normally developing myocardium. These 44 genes had significant negative correlations with 33 microRNAs, each of which also had significantly changed expression. Here, we focus on miR-421, as it is significantly upregulated in RV tissue from infants with TOF; is predicted to interact with multiple members of cardiovascular regulatory pathways; and has been shown to regulate cell proliferation. We knocked down, and over expressed miR-421 in primary cells derived from the RV of infants with TOF, and infants with normally developing hearts, respectively. We found a significant inverse correlation between the expression of miR-421 and SOX4, a key regulator of the Notch pathway, which has been shown to be important for the cardiac outflow track. These findings suggest that the dysregulation of miR-421 warrants further investigation as a potential contributor to tetralogy of Fallot.

Noncoding RNA expression in myocardium from infants with tetralogy of Fallot.

BACKGROUND: The importance of noncoding RNAs (ncRNA), especially microRNAs (miRNAs), for maintaining stability in the developing vertebrate heart has recently become apparent; however, there is little known about the expression pattern of ncRNA in the human heart with developmental anomalies. METHODS AND RESULTS: We examined the expression of miRNAs and small nucleolar RNAs (snoRNAs) in right ventricular myocardium from 16 infants with nonsyndromic tetralogy of Fallot (TOF) without a 22q11.2 deletion, 3 fetal heart samples, and 8 normally developing infants. We found 61 miRNAs and 135 snoRNAs to be significantly changed in expression in myocardium from children with TOF compared with normally developing comparison subjects. The pattern of ncRNA expression in TOF myocardium had a surprising resemblance to expression patterns in fetal myocardium, especially for the snoRNAs. Potential targets of miRNAs with altered expression were enriched for gene networks of importance to cardiac development. We derived a list of 229 genes known to be critical to heart development and found 44 had significantly changed expression in TOF myocardium relative to normally developing myocardium. These 44 genes had significant negative correlation with 33 miRNAs, each of which also had significantly changed expression. The primary function of snoRNAs is targeting specific nucleotides of ribosomal RNAs and spliceosomal RNAs for biochemical modification. The targeted nucleotides of the differentially expressed snoRNAs were concentrated in the 28S and 18S ribosomal RNAs and 2 spliceosomal RNAs, U2 and U6. In addition, in myocardium from children with TOF, we observed splicing variants in 51% of genes that are critical for cardiac development. Taken together, these observations suggest a link between levels of snoRNA that target spliceosomal RNAs, spliceosomal function, and heart development. CONCLUSIONS: This is the first report characterizing ncRNA expression in a congenital heart defect. The striking shift in expression of ncRNAs reflects a fundamental change in cell biology, likely impacting expression, transcript splicing, and translation of developmentally important genes and possibly contributing to the cardiac defect.

Initial pediatric cardiac experience with decellularized allograft patches.

PURPOSE: This study examines use patterns, early outcomes, and technical surgical adaptability of a newly approved decellularized allograft pulmonary artery patch for right ventricular outflow tract reconstructions in neonates and infants, including primary operations and reoperations. DESCRIPTION: The study includes the 44 consecutive initial patients in which 46 patches were used for cardiovascular reconstruction between September 2009 and September 2010. Recorded variables include sex, age at operation, adverse outcome end points (eg, death, stenosis, aneurysm), congenital diagnoses, postoperative complications, and number, type, and location of patches. EVALUATION: Patients were a mean age of 290±343 days at operation, and 54.5% were boys. Three types of patch were used: 58.7% thin, 21.7% thick, and 19.6% hemipulmonary. No device-related deaths or adverse events occurred. A biopsy specimen of one patch at elective reoperation demonstrated active recellularization, with no inflammation. CONCLUSIONS: These patches have a wide range of applicability. Handling and technical flexibility is excellent and superior to standard options. There appears to be potential for autologous revitalization of the tissue.

Gene expression in cardiac tissues from infants with idiopathic conotruncal defects.

BACKGROUND: Tetralogy of Fallot (TOF) is the most commonly observed conotruncal congenital heart defect. Treatment of these patients has evolved dramatically in the last few decades, yet a genetic explanation is lacking for the failure of cardiac development for the majority of children with TOF. Our goal was to perform genome wide analyses and characterize expression patterns in cardiovascular tissue (right ventricle, pulmonary valve and pulmonary artery) obtained at the time of reconstructive surgery from 19 children with tetralogy of Fallot. METHODS: We employed genome wide gene expression microarrays to characterize cardiovascular tissue (right ventricle, pulmonary valve and pulmonary artery) obtained at the time of reconstructive surgery from 19 children with TOF (16 idiopathic and three with 22q11.2 deletions) and compared gene expression patterns to normally developing subjects. RESULTS: We detected a signal from approximately 26,000 probes reflecting expression from about half of all genes, ranging from 35% to 49% of array probes in the three tissues. More than 1,000 genes had a 2-fold change in expression in the right ventricle (RV) of children with TOF as compared to the RV from matched control infants. Most of these genes were involved in compensatory functions (e.g., hypertrophy, cardiac fibrosis and cardiac dilation). However, two canonical pathways involved in spatial and temporal cell differentiation (WNT, p = 0.017 and Notch, p = 0.003) appeared to be generally suppressed. CONCLUSIONS: The suppression of developmental networks may represent a remnant of a broad malfunction of regulatory pathways leading to inaccurate boundary formation and improper structural development in the embryonic heart. We suggest that small tissue specific genomic and/or epigenetic fluctuations could be cumulative, leading to regulatory network disruption and failure of proper cardiac development.

The nonfenestrated extracardiac Fontan procedure: a cohort of 145 patients.

BACKGROUND: There are limited data available on the outcomes of single-ventricle patients who have undergone a nonfenestrated extracardiac Fontan procedure. This study examined the clinical experience of a large cohort of patients from a single institution who received this procedure. METHODS: A retrospective data set of 145 patients who underwent a nonfenestrated extracardiac Fontan procedure from July 1997 to September 2008 was reviewed. RESULTS: The hospital survival was 94.5%. Takedown of the Fontan conduit was necessary in 4 patients (2.8%), and 3 of these 4 patients were also operative deaths. Although female sex (p = 0.048), cardiopulmonary bypass time (p = 0.002), and aortic cross-clamp time (p = 0.007) were found to be significant in the univariate analysis, only sex (p = 0.035; odds ratio, 3.869; 95% confidence limits, 1.097 to 13.644) and cardiopulmonary bypass time in minutes (p = 0.001; odds ratio, 1.023; 95% confidence limits, 1.009 to 1.037) were found to be significant in the multivariate analysis for hospital survival. The late survival was 95.6% (131 of 137 patients) with a mean follow-up of 3.3 years (range, 0.0 to 10.8 years). The freedom from Fontan failure was 92% at 1 year, 89% at 5 years, and 82% at 10 years. Stepwise logistic regression found cardiopulmonary bypass time (p = 0.003; odds ratio, 1.023; 95% confidence limits, 1.008 to 1.039) to be a significant risk factor for late survival. CONCLUSIONS: The nonfenestrated extracardiac Fontan procedure can be successfully used in the palliation of single-ventricle patients.

Intraoperative hyperglycemia and postoperative bacteremia in the pediatric cardiac surgery patient.

BACKGROUND: Intraoperative hyperglycemia has been found to be associated with a higher incidence of postoperative infections in the adult cardiac surgery population. The goal of this study was to determine the association of intraoperative hyperglycemia and postoperative bacteremia in the pediatric population. METHODS: A retrospective chart review of all cardiac surgical cases for patients 18 years of age or younger requiring cardiopulmonary bypass support between June 2002 and July 2007 yielded 1,132 total cases representing 992 unique patients. Patient demographic and clinical data of interest were collected. Descriptive statistics and regression analyses were performed to investigate the hypothesized relationship between glucose levels and infection rates. RESULTS: From the 992 patient records examined, 15 patients exhibited a bacteremia within 14 days of surgery (1.5%). The association between the highest glucose during cardiopulmonary bypass and bacteremia reached statistical significance when the glucose level reached 175 mg/dL (chi(2) = 4.59, 1 degree of freedom; p = 0.032). A patient was more than three times as likely to have a postoperative bacteremia when the glucose level reached this amount or exceeded it (odds ratio, 3.3, 95% confidence interval, 1.04 to 10.39). Ten of the 15 (66.7%) postoperative infections occurred in patients with peak bypass glucose levels of at least 175 mg/dL. CONCLUSIONS: Intraoperative hyperglycemia was found to be associated with a higher risk of postoperative bacteremia in the pediatric cardiac surgery population.