Arginine-NO metabolites are associated with morbidity in single ventricle infants undergoing stage 2 palliation.

BACKGROUND: Infants with single ventricle heart disease (SVHD) suffer morbidity from insufficient pulmonary blood flow, which may be related to impaired arginine metabolism. No prior study has reported quantitative mapping of arginine metabolites to evaluate the relationship between circulating metabolite levels and outcomes. METHODS: Prospective cohort study of 75 SVHD cases peri-Stage 2 and 50 healthy controls. We targeted pre- and post-op absolute serum quantification of 9 key members of the arginine metabolism pathway by tandem mass spectrometry. Primary outcomes were length of stay (LOS) and post-Stage 2 hypoxemia. RESULTS: Pre-op cases showed alteration in 6 metabolites including decreased arginine and increased asymmetric dimethyl arginine (ADMA) levels compared to controls. Post-op cases demonstrated decreased arginine and citrulline levels persisting through 48 h. Adjusting for clinical variables, lower pre-op and 2 h post-op concentrations of multiple metabolites, including arginine and citrulline, were associated with longer post-op LOS (p < 0.01). Increased ADMA at 24 h was associated with greater post-op hypoxemia burden (p < 0.05). CONCLUSION: Arginine metabolism is impaired in interstage SVHD infants and is further deranged following Stage 2 palliation. Patients with greater metabolite alterations experience greater post-op morbidity. Decreased arginine metabolism may be an important driver of pathology in SVHD. IMPACT: Interstage infants with SVHD have significantly altered arginine-nitric oxide metabolism compared to healthy children with deficiency of multiple pathway intermediates persisting through 48 h post-Stage 2 palliation. After controlling for clinical covariates and classic catheterization-derived predictors of Stage 2 readiness, both lower pre-operation and lower post-operation circulating metabolite levels were associated with longer post-Stage 2 LOS while increased post-Stage 2 ADMA concentration was associated with greater post-op hypoxemia. Arginine metabolism mapping offers potential for development using personalized medicine strategies as a biomarker of Stage 2 readiness and therapeutic target to improve pulmonary vascular health in infants with SVHD.

Metabolomic profiling demonstrates evidence for kidney and urine metabolic dysregulation in a piglet model of cardiac surgery-induced acute kidney injury.

Acute kidney injury (AKI) is a common cause of morbidity after congenital heart disease surgery. Progress on diagnosis and therapy remains limited, however, in part due to poor mechanistic understanding and a lack of relevant translational models. Metabolomic approaches could help identify novel mechanisms of injury and potential therapeutic targets. In the present study, we used a piglet model of cardiopulmonary bypass with deep hypothermic circulatory arrest (CPB/DHCA) and targeted metabolic profiling of kidney tissue, urine, and serum to evaluate metabolic changes specific to animals with histological acute kidney injury. CPB/DHCA animals with acute kidney injury were compared with those without acute kidney injury and mechanically ventilated controls. Acute kidney injury occurred in 10 of 20 CPB/DHCA animals 4 h after CPB/DHCA and 0 of 7 control animals. Injured kidneys showed a distinct tissue metabolic profile compared with uninjured kidneys (R2 = 0.93, Q2 = 0.53), with evidence of dysregulated tryptophan and purine metabolism. Nine urine metabolites differed significantly in animals with acute kidney injury with a pattern suggestive of increased aerobic glycolysis. Dysregulated metabolites in kidney tissue and urine did not overlap. CPB/DHCA strongly affected the serum metabolic profile, with only one metabolite that differed significantly with acute kidney injury (pyroglutamic acid, a marker of oxidative stress). In conclusion, based on these findings, kidney tryptophan and purine metabolism are candidates for further mechanistic and therapeutic investigation. Urine biomarkers of aerobic glycolysis could help diagnose early acute kidney injury after CPB/DHCA and warrant further evaluation. The serum metabolites measured at this early time point did not strongly differentiate based on acute kidney injury.NEW & NOTEWORTHY This project explored the metabolic underpinnings of postoperative acute kidney injury (AKI) following pediatric cardiac surgery in a translationally relevant large animal model of cardiopulmonary bypass with deep hypothermic circulatory arrest. Here, we present novel evidence for dysregulated tryptophan catabolism and purine catabolism in kidney tissue and increased urinary glycolysis intermediates in animals who developed histological AKI. These pathways represent potential diagnostic and therapeutic targets for postoperative AKI in this high-risk population.

Changes in infant porcine pulmonary tissue oxylipins induced by cardiopulmonary bypass.

BACKGROUND: Oxylipins are metabolites derived from fatty acids such as arachidonic acid (AA) and are key mediators in inflammation, host defense, and tissue injury. Serum oxylipins increase in adults after cardiopulmonary bypass (CPB) but tissue-level changes are poorly defined. The objective of this study was to characterize pulmonary tissue oxylipins in an infant porcine model of CPB with deep hypothermic circulatory arrest (DHCA). METHODS: Infant pigs underwent CPB with DHCA. Controls received anesthesia only. Right upper and lower lobes of the lung underwent oxylipin analysis via liquid chromatography-tandem mass spectrometry. One-way ANOVA was utilized to assess differences in oxylipin concentrations across groups, followed by pairwise comparisons. RESULTS: AA and multiple AA metabolites via cytochrome P450 (CYP450), lipoxygenase (LOX), and cyclooxygenase (COX) pathways were significantly increased in the upper and lower lobe of pigs exposed to CPB/DHCA as compared to controls. Multiple prostaglandin metabolites produced via COX were also significantly elevated in the lower lobes of control animals. CONCLUSIONS: CPB/DHCA induces a significant increase in pulmonary tissue AA, with subsequent metabolism via COX, LOX, and CYP450 pathways. Interestingly, prostaglandins were also elevated in the lower lobes of the controls, suggesting a mechanism separate from CPB/DHCA. Future oxylipin studies are needed to better understand CPB-induced acute lung injury. IMPACT: CPB/DHCA and, to a lesser extent, lung region influence pulmonary tissue-level AA metabolite production. Inflammatory mediator AA metabolites have been noted in previous studies to increase following CPB; however, this is the first study to look at pulmonary tissue-level differences following CPB/DHCA. Increases in many AA metabolites, including LOX- and CYP450-derived products, were seen in both upper and lower lobe of piglets following CPB/DHCA. COX-derived prostaglandin metabolites were increased not only in CPB upper and lower lobe but also in mechanically ventilated control lower lobe, suggesting an additional, separate mechanism from CPB/DCHA.

Regional lung metabolic profile in a piglet model of cardiopulmonary bypass with circulatory arrest.

INTRODUCTION: Acute lung injury is common following cardiopulmonary bypass and deep hypothermic circulatory arrest for congenital heart surgery with the most severe injury in the dorsocaudal lung. Metabolomics offers promise in deducing mechanisms of disease states, providing risk stratification, and understanding therapeutic responses in regards to CPB/DHCA related organ injury. OBJECTIVES: Using an infant porcine model, we sought to determine the individual and additive effects of CPB/DHCA and lung region on the metabolic fingerprint, metabolic pathways, and individual metabolites in lung tissue. METHODS: Twenty-seven infant piglets were divided into two groups: mechanical ventilation + CPB/DHCA (n = 20) and mechanical ventilation only (n = 7). Lung tissue was obtained from dorsocaudal and ventral regions. Targeted analysis of 235 metabolites was performed using HPLC/MS-MS. Data was analyzed using Principal Component Analysis (PCA), Partial Least Square Discriminant Analysis (PLS-DA), ANOVA, and pathway analysis. RESULTS: Profound metabolic differences were found in dorsocaudal compared to ventral lung zones by PCA and PLS-DA (R2 = 0.7; Q2 = 0.59; p < 0.0005). While overshadowed by the regional differences, some differences by exposure to CPB/DHCA were seen as well. Seventy-four metabolites differed among groups and pathway analysis revealed 20 differential metabolic pathways. CONCLUSION: Our results demonstrate significant metabolic disturbances between dorsocaudal and ventral lung regions during supine mechanical ventilation with or without CPB/DHCA. CPB/DHCA also leads to metabolic differences and may have additive effects to the regional disturbances. Most pathways driving this pathology are involved in energy metabolism and the metabolism of amino acids, carbohydrates, and reduction-oxidation pathways.

Serum metabolic profile of postoperative acute kidney injury following infant cardiac surgery with cardiopulmonary bypass.

BACKGROUND: We sought to determine differences in the circulating metabolic profile of infants with or without acute kidney injury (AKI) following cardiothoracic surgery with cardiopulmonary bypass (CPB). METHODS: We performed a secondary analysis of preoperative and 24-h postoperative serum samples from infants ≤ 120 days old undergoing CPB. Metabolic profiling of the serum samples was performed by targeted analysis of 165 serum metabolites via tandem mass spectrometry. We then compared infants who did or did not develop AKI in the first 72 h postoperatively to determine global differences in the preoperative and 24-h metabolic profiles in addition to specific differences in individual metabolites. RESULTS: A total of 57 infants were included in the study. Six infants (11%) developed KDIGO stage 2/3 AKI and 13 (23%) developed stage 1 AKI. The preoperative metabolic profile did not differentiate between infants with or without AKI. Infants with severe AKI could be moderately distinguished from infants without AKI by their 24-h metabolic profile, while infants with stage 1 AKI segregated into two groups, overlapping with either the no AKI or severe AKI groups. Differences in these 24-h metabolic profiles were driven by 21 metabolites significant at an adjusted false discovery rate of < 0.05. Prominently altered pathways include purine, methionine, and kynurenine/nicotinamide metabolism. CONCLUSION: Moderate-to-severe AKI after infant cardiac surgery is associated with changes in the serum metabolome, including prominent changes to purine, methionine, and kynurenine/nicotinamide metabolism. A portion of infants with mild AKI demonstrated similar metabolic changes, suggesting a potential role for metabolic analysis in the evaluation of lower stage injury.

Novel measures of left ventricular electromechanical discoordination predict clinical outcomes in children with pulmonary arterial hypertension.

Adverse ventricle-ventricle interaction and resultant left ventricular (LV) dysfunction are a recognized pathophysiological component of disease progression in pulmonary arterial hypertension (PAH) and can be associated with electrical and mechanical dyssynchrony. The purpose of this study was to investigate the clinical and mechanistic implications of LV electromechanical dyssynchrony in children with PAH by using novel systolic stretch and diastolic relaxation discoordination indexes derived noninvasively from cardiac MRI (CMR). In children with PAH referred for CMR (n = 64) and healthy controls (n = 20), we calculated two novel markers of ventricular discoordination, systolic stretch fraction (SSF) and diastolic relaxation fraction (DRF). SSF and DRF were evaluated with respect to 1) electrical dyssynchrony, 2) functional status, and 3) composite clinical outcomes. SSF was increased in patients with PAH compared with controls (P = 0.004). There was no difference in DRF between PAH and control groups. There were no differences between groups in standard mechanical dyssynchrony and LV global circumferential strain. Increased SSF was associated with greater electrical dyssynchrony (QRS duration) as well as worse WHO functional class. SSF, DRF, mechanical dyssynchrony, and right ventricular (RV) volumes were prognostic for worse clinical outcomes. LV dyssynchrony indexes are altered in pediatric patients with PAH compared with controls in proportion with greater degrees of RV dilation. Patients with PAH with greater dyssynchrony have worse clinical outcomes. RV-induced increased LV electromechanical dyssynchrony therefore may be an important link in the causal pathway from PAH to clinically significant LV dysfunction. Since dyssynchrony could precede overt LV dysfunction, addition of ventricular synchrony analysis to CMR postprocessing protocols may be of clinical benefit.NEW & NOTEWORTHY We demonstrate that left ventricular discoordination indexes are altered in pediatric patients with pulmonary arterial hypertension compared with controls and pediatric patients with pulmonary arterial hypertension with greater dyssynchrony have worse clinical outcomes. Furthermore, there is evidence for the mechanism of right ventricular-induced left ventricular discoordination to include a combination of delayed early systolic electromechanical activation, late-systolic septal shift, and prolonged, postsystolic septal thickening.

Activation of kynurenine pathway of tryptophan metabolism after infant cardiac surgery with cardiopulmonary bypass: a prospective cohort study.

BACKGROUND: Serum kynurenic acid is associated with poor outcomes after infant cardiopulmonary bypass (CPB), but comprehensive mapping of the kynurenine pathway (KP) after CPB has yet to be performed. AIMS: To map changes in the KP induced by infant CPB. METHODS: Compared changes in serum KP metabolites through 48hrs post-op with liquid-chromatography-tandem mass spectrometry. RESULTS: Infant CPB results in marked increase in proximal, but not distal metabolites of the KP. CONCLUSIONS: Infant CPB leads to accumulation of circulating KP metabolites, which have important neurologic and immunologic activities. Thus, further exploration of the KP is warranted in these high-risk infants.

Validity of administrative claims-based algorithms for ventricular arrhythmia and cardiac arrest in the pediatric population.

PURPOSE: Identify administrative claims-based algorithms for capturing out-of-hospital ventricular arrhythmias (VA) and cardiac arrests (CA) due to cardiac causes in the pediatric population with high positive-predictive value (PPV). METHODS: Within a single pediatric center, a retrospective cohort of patients hospitalized or seen in the emergency room for VA or CA were identified from the electronic health records. Eligible encounters were blindly reviewed and linked to administrative data, including ICD-9/ICD-10 codes. Test characteristics, including PPV, for different diagnostic and procedure codes were generated using a 50% training sample. The gold standard was definite or suspected out-of-hospital VA or CA due to cardiac cause verified based on clinical criteria. Algorithms with the highest PPV were then applied to a 50% validation sample to validate performance. RESULTS: From 2004-2017, 598 encounters met eligibility criteria. 174 (29%) had an outcome of interest, with remainder being an inpatient event or CA due to other cause. Within the training sample (n = 263), VA codes in primary position had a PPV 94% (95%CI 81%-99%) with low sensitivity (44%, 95%CI 33%-56%). CA codes in any position or VA codes in nonprimary positions had low PPV (18%-19%, 31% respectively). Applying the top three performing algorithms to the validation sample (n = 252) yielded similar PPV values. CONCLUSIONS: Contrary to adults, algorithms including a CA code do not perform well for identifying out-of-hospital VA and CA due to cardiac cause in the pediatric populations. Researchers should be aware of the potential implications for future pediatric drug safety studies for these outcomes.

Infant cardiopulmonary bypass: CD73 kinetics, association with clinical outcomes, and influence on serum adenosine production capacity.

BackgroundExtracellular adenine nucleotides contribute to ischemia-reperfusion injury following infant cardiopulmonary bypass (CPB), whereas conversion to adenosine may be protective. Alkaline phosphatase (AP), a key enzyme responsible for this conversion, decreases after infant CPB. Indirect evidence suggests that soluble CD73 may simultaneously increase and partially offset this loss of AP. We sought to measure CD73 levels in infants undergoing CPB and determine its association with adenosine production capacity and postoperative support requirements.MethodsA prospective cohort study of infants ≤120 days of age undergoing CPB. CD73 was measured before CPB and during rewarming. Multivariable modeling evaluated the contributions of CD73/AP to adenosine production capacity and postoperative support requirements.ResultsSerum samples from 85 subjects were analyzed. The median CD73 concentration increased following CPB (95.2 vs. 179.8 ng/ml; P<0.0001). Rewarming CD73 was independently inversely associated with vasoactive inotropic support (P<0.005) and length of intensive care unit stay (P<0.005). Combined AP activity and CD73 concentration predicted adenosine production capacity (P<0.0001).ConclusionsSerum CD73 increases following infant CPB. Low rewarming CD73 is independently associated with increased postoperative support requirements. CD73 and AP together predict serum adenosine production capacity and may represent potential therapeutic targets to clear extracellular adenine nucleotides and improve outcomes following infant CPB.

Alkaline Phosphatase in Infant Cardiopulmonary Bypass: Kinetics and Relationship to Organ Injury and Major Cardiovascular Events.

OBJECTIVES: To determine the kinetics of alkaline phosphatase (AP) activity and concentration after infant cardiopulmonary bypass, including isoform-specific changes, and to measure the association between postoperative AP activity and major postoperative cardiovascular events, organ injury/dysfunction, and postoperative support requirements STUDY DESIGN: Prospective cohort study of 120 infants ≤120 days of age undergoing cardiopulmonary bypass. AP total and isoform-specific activity was assessed at 6 time points (preoperation, rewarming, 6, 24, 48, and 72 hours postoperation). Low AP activity was defined as ≤80 U/L. AP concentrations and biomarkers of organ injury/dysfunction were collected through 24 hours postoperation. Major cardiovascular events were defined as cardiac arrest, mechanical circulatory support, or death. RESULTS: AP activity loss occurred primarily during the operation (median decrease 89 U/L; P < .0001) secondary to decreased bone and liver 2 isoforms. Activity declined through 24 hours in 27% of patients. AP activity strongly correlated with serum concentration (r = 0.87-0.91; P < .0001). Persistent low AP activity at 72 hours was associated independently with occurrence of a major cardiac event (OR 5.6; P < .05). Early AP activity was associated independently with subsequent vasoactive-inotropic score (P < .001), peak lactate (P < .0001), peak creatinine (P < .0005), N-terminal pro-brain natriuretic peptide (P < .05), and intestinal fatty acid binding protein (P < .005). CONCLUSIONS: AP activity decreases during infant cardiopulmonary bypass and may continue to decrease for 24 hours. Activity loss is secondary to decreased bone and liver 2 isoform concentrations. Early low AP activity is associated independently with subsequent postoperative support and organ injury/dysfunction, and persistence of AP activity ≤80 U/L at 72 hours is associated independently with increased odds of major cardiovascular events.

Validation of the Vasoactive-Inotropic Score in Pediatric Sepsis.

OBJECTIVES: To assess the validity of Vasoactive-Inotropic Score as a scoring system for cardiovascular support and surrogate outcome in pediatric sepsis. DESIGN: Secondary retrospective analysis of a single-center sepsis registry. SETTING: Freestanding children's hospital and tertiary referral center. PATIENTS: Children greater than 60 days and less than 18 years with sepsis identified in the emergency department between January 2012 and June 2015 treated with at least one vasoactive medication within 48 hours of admission to the PICU. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Vasoactive-Inotropic Score was abstracted at 6, 12, 24, and 48 hours post ICU admission. Primary outcomes were ventilator days and ICU length of stay. The secondary outcome was a composite outcome of cardiac arrest/extracorporeal membrane oxygenation/in-hospital mortality. One hundred thirty-eight patients met inclusion criteria. Most common infectious sources were pneumonia (32%) and bacteremia (23%). Thirty-three percent were intubated and mortality was 6%. Of the time points assessed, Vasoactive-Inotropic Score at 48 hours showed the strongest correlation with ICU length of stay (r = 0.53; p < 0.0001) and ventilator days (r = 0.52; p < 0.0001). On multivariable analysis, Vasoactive-Inotropic Score at 48 hours was a strong independent predictor of primary outcomes and intubation. For every unit increase in Vasoactive-Inotropic Score at 48 hours, there was a 13% increase in ICU length of stay (p < 0.001) and 8% increase in ventilator days (p < 0.01). For every unit increase in Vasoactive-Inotropic Score at 12 hours, there was a 14% increase in odds of having the composite outcome (p < 0.01). CONCLUSIONS: Vasoactive-Inotropic Score in pediatric sepsis patients is independently associated with important clinically relevant outcomes including ICU length of stay, ventilator days, and cardiac arrest/extracorporeal membrane oxygenation/mortality. Vasoactive-Inotropic Score may be a useful surrogate outcome in pediatric sepsis.

Circulating biomarkers of extracellular matrix dysregulation are associated with adverse post-stage 2 outcomes in infants with single ventricle heart disease.

Children with single ventricle heart disease (SVHD) experience morbidity due to inadequate pulmonary blood flow. Using proteomic screening, our group previously identified members of the matrix metalloproteinase (MMP), tissue inhibitor of metalloproteinase (TIMP), and fibroblast growth factor (FGF) families as potentially dysregulated in SVHD. No prior study has taken a targeted approach to mapping circulating levels of these protein families or their relationship to pulmonary vascular outcomes in SVHD. We performed a prospective cohort study of 70 SVHD infants pre-Stage 2 palliation and 24 healthy controls. We report targeted serum quantification of 39 proteins in the MMP, TIMP, and FGF families using the SomaScan platform. Clinical variables were extracted from the medical record. Twenty of 39 tested proteins (7/14 MMPs, 2/4 TIMPs, and 11/21 FGFs) differed between cases and controls. On single variable testing, 6 proteins and no clinical covariates were associated with both post-Stage 2 hypoxemia and length of stay. Multiple-protein modeling identified increased circulating MMP 7 and MMP 17, and decreased circulating MMP 8 and FGFR2 as most associated with post-Stage 2 hypoxemia; increased MMP 7 and TIMP 4 and decreased circulating MMP 1 and MMP 8 were most associated with post-operation length of stay. The MMP, TIMP, and FGF families are altered in SVHD. Pre-Stage 2 imbalance of extracellular matrix (ECM) proteins-increased MMP 7 and decreased MMP 8-was associated with multiple adverse post-operation outcomes. Maintenance of the ECM may be an important pathophysiologic driver of Stage 2 readiness in SVHD.

Piglet cardiopulmonary bypass induces intestinal dysbiosis and barrier dysfunction associated with systemic inflammation.

The intestinal microbiome is essential to human health and homeostasis, and is implicated in the pathophysiology of disease, including congenital heart disease and cardiac surgery. Improving the microbiome and reducing inflammatory metabolites may reduce systemic inflammation following cardiac surgery with cardiopulmonary bypass (CPB) to expedite recovery post-operatively. Limited research exists in this area and identifying animal models that can replicate changes in the human intestinal microbiome after CPB is necessary. We used a piglet model of CPB with two groups, CPB (n=5) and a control group with mechanical ventilation (n=7), to evaluate changes to the microbiome, intestinal barrier dysfunction and intestinal metabolites with inflammation after CPB. We identified significant changes to the microbiome, barrier dysfunction, intestinal short-chain fatty acids and eicosanoids, and elevated cytokines in the CPB/deep hypothermic circulatory arrest group compared to the control group at just 4 h after intervention. This piglet model of CPB replicates known human changes to intestinal flora and metabolite profiles, and can be used to evaluate gut interventions aimed at reducing downstream inflammation after cardiac surgery with CPB.

Interstage Single Ventricle Heart Disease Infants Show Dysregulation in Multiple Metabolic Pathways: Targeted Metabolomics Analysis.

BACKGROUND: Infants with SVHD experience morbidity related to pulmonary vascular inadequacy. Metabolomic analysis involves a systems biology approach to identifying novel biomarkers and pathways in complex diseases. The metabolome of infants with SVHD is not well understood and no prior study has evaluated the relationship between serum metabolite patterns and pulmonary vascular readiness for staged SVHD palliation. OBJECTIVES: The purpose of this study was to evaluate the circulating metabolome of interstage infants with single ventricle heart disease (SVHD) and determine whether metabolite levels were associated with pulmonary vascular inadequacy. METHODS: This was a prospective cohort study of 52 infants with SVHD undergoing Stage 2 palliation and 48 healthy infants. Targeted metabolomic phenotyping (175 metabolites) was performed by tandem mass spectrometry on SVHD pre-Stage 2, post-Stage 2, and control serum samples. Clinical variables were extracted from the medical record. RESULTS: Random forest analysis readily distinguished between cases and controls and preoperative and postoperative samples. Seventy-four of 175 metabolites differed between SVHD and controls. Twenty-seven of 39 metabolic pathways were altered including pentose phosphate and arginine metabolism. Seventy-one metabolites differed in SVHD patients between timepoints. Thirty-three of 39 pathways were altered postoperatively including arginine and tryptophan metabolism. We found trends toward increased preoperative methionine metabolites in patients with higher pulmonary vascular resistance and higher postoperative tryptophan metabolites in patients with greater postoperative hypoxemia. CONCLUSIONS: The circulating metabolome of interstage SVHD infants differs significantly from controls and is further disrupted after Stage 2. Several metabolites showed trends toward association with adverse outcomes. Metabolic dysregulation may be an important factor in early SVHD pathobiology.

The proteomic fingerprint in infants with single ventricle heart disease in the interstage period: evidence of chronic inflammation and widespread activation of biological networks.

Introduction: Children with single ventricle heart disease (SVHD) experience significant morbidity across systems and time, with 70% of patients experiencing acute kidney injury, 33% neurodevelopmental impairment, 14% growth failure, and 5.5% of patients suffering necrotizing enterocolitis. Proteomics is a method to identify new biomarkers and mechanisms of injury in complex physiologic states. Methods: Infants with SVHD in the interstage period were compared to similar-age healthy controls. Serum samples were collected, stored at -80°C, and run on a panel of 1,500 proteins in single batch analysis (Somalogic Inc., CO). Partial Least Squares-Discriminant Analysis (PLS-DA) was used to compare the proteomic profile of cases and controls and t-tests to detect differences in individual proteins (FDR <0.05). Protein network analysis with functional enrichment was performed in STRING and Cytoscape. Results: PLS-DA readily discriminated between SVHD cases (n = 33) and controls (n = 24) based on their proteomic pattern alone (Accuracy = 0.96, R2 = 0.97, Q2 = 0.80). 568 proteins differed between groups (FDR <0.05). We identified 25 up-regulated functional clusters and 13 down-regulated. Active biological systems fell into six key groups: angiogenesis and cell proliferation/turnover, immune system activation and inflammation, altered metabolism, neural development, gastrointestinal system, and cardiac physiology and development. Conclusions: We report a clear differentiation in the circulating proteome of patients with SVHD and healthy controls with >500 circulating proteins distinguishing the groups. These proteomic data identify widespread protein dysregulation across multiple biologic systems with promising biological plausibility as drivers of SVHD morbidity.

Increased Circulating Endothelin 1 Is Associated With Postoperative Hypoxemia in Infants With Single-Ventricle Heart Disease Undergoing Superior Cavopulmonary Anastomosis.

Background Inadequate pulmonary vascular growth results in morbidity for many children with single-ventricle heart disease (SVHD). Endothelin 1 (ET1) is a potent vasoconstrictor and stimulator of pulmonary artery smooth muscle proliferation. Circulating ET1 levels and their association with outcomes have not been studied during early SVHD palliation. We aimed to define circulating levels of ET1 in patients with SVHD undergoing stage 2 palliation and evaluate their relationship to postoperative hypoxemia. We hypothesized that patients with SVHD with higher ET1 concentration would have a greater post-stage 2 hypoxemia. Methods and Results Prospective cohort study of 55 subjects with SVHD undergoing stage 2 palliation and 50 controls. Samples for ET1 analysis were collected at preoperation (systemic and pulmonary vein) and 2, 24, and 48 hours postoperation for cases and a single time point for controls. The primary outcome was percentage of first 48 postoperative hours with clinically significant hypoxemia (saturation, <70%). ET1 concentration was lower in preoperative cases than controls (2.2 versus 2.7 pg/mL; P=0.0015) and in the pulmonary vein than systemic vein (1.7 versus 2.2 pg/mL; P<0.001). ET1 level increased by 2 hours postoperation and trended back to baseline by 48 hours. Higher preoperative pulmonary vein ET1 and 2 hours postoperative ET1 were associated with larger hypoxemia burden (10.6% versus 2.7% [P=0.0081]; and 7.6% versus 3.2% [P=0.01], respectively). Multivariable testing demonstrated ET1 concentration and cardiopulmonary bypass time were associated with hypoxemia, whereas catheterization measurements and clinical variables were not. Conclusions Infants with SVHD with higher perioperative ET1 concentration experience more post-stage 2 hypoxemia. ET1 activity may be a modifiable risk factor of pulmonary vascular inadequacy for stage 2 palliation.

Validation of Point-of-Care Ultrasound to Measure Perioperative Edema in Infants With Congenital Heart Disease.

Purpose: Fluid overload is a common post-operative issue in children following cardiac surgery and is associated with increased morbidity and mortality. There is currently no gold standard for evaluating fluid status. We sought to validate the use of point-of-care ultrasound to measure skin edema in infants and assess the intra- and inter-user variability. Methods: Prospective cohort study of neonates (≤30 d/o) and infants (31 d/o to 12 m/o) undergoing cardiac surgery and neonatal controls. Skin ultrasound was performed on four body sites at baseline and daily post-operatively through post-operative day (POD) 3. Subcutaneous tissue depth was manually measured. Intra- and inter-user variability was assessed using intraclass correlation coefficient (ICC). Results: Fifty control and 22 surgical subjects underwent skin ultrasound. There was no difference between baseline surgical and control neonates. Subcutaneous tissue increased in neonates starting POD 1 with minimal improvement by POD 3. In infants, this pattern was less pronounced with near resolution by POD 3. Intra-user variability was excellent (ICC 0.95). Inter-user variability was very good (ICC 0.82). Conclusion: Point-of-care skin ultrasound is a reproducible and reliable method to measure subcutaneous tissue in infants with and without congenital heart disease. Acute increases in subcutaneous tissue suggests development of skin edema, consistent with extravascular fluid overload. There is evidence of skin edema starting POD 1 in all subjects with no substantial improvement by POD 3 in neonates. Point-of-care ultrasound could be an objective way to measure extravascular fluid overload in infants. Further research is needed to determine how extravascular fluid overload correlates to clinical outcomes.