Oxidative stress markers are not associated with outcomes after pediatric heart surgery

Exploring the feasibility of using long-term stored newborn dried blood spots to identify metabolic features for congenital heart disease screening

Congenital heart disease (CHD) represents a significant contributor to both morbidity and mortality in neonates and children. There's currently no analogous dried blood spot (DBS) screening for CHD immediately after birth. This study was set to assess the feasibility of using DBS to identify reliable metabolite biomarkers with clinical relevance, with the aim to screen and classify CHD utilizing the DBS. We assembled a cohort of DBS datasets from the California Department of Public Health (CDPH) Biobank, encompassing both normal controls and three pre-defined CHD categories. A DBS-based quantitative metabolomics method was developed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). We conducted a correlation analysis comparing the absolute quantitated metabolite concentration in DBS against the CDPH NBS records to verify the reliability of metabolic profiling. For hydrophilic and hydrophobic metabolites, we executed significant pathway and metabolite analyses respectively. Logistic and LightGBM models were established to aid in CHD discrimination and classification. Consistent and reliable quantification of metabolites were demonstrated in DBS samples stored for up to 15 years. We discerned dysregulated metabolic pathways in CHD patients, including deviations in lipid and energy metabolism, as well as oxidative stress pathways. Furthermore, we identified three metabolites and twelve metabolites as potential biomarkers for CHD assessment and subtypes classifying. This study is the first to confirm the feasibility of validating metabolite profiling results using long-term stored DBS samples. Our findings highlight the potential clinical applications of our DBS-based methods for CHD screening and subtype classification.

Elevated oxidative stress in patients with congenital heart disease and the effect of cyanosis: a meta-analysis

Oxidative stress is an important pathophysiological mechanism in the development of numerous cardiovascular disorders. To improve therapy and preventive strategies, clinicians need a better understanding of the underlying pathophysiological mechanisms of congenital heart diseases (CHD). The objective of this meta-analysis was to determine whether oxidative stress is elevated in patients with CHD compared to healthy controls, and to evaluate whether a difference in oxidative stress parameters can be observed between patients with cyanotic (cCHD) and acyanotic CHD (aCHD). Therefore, 21 studies investigating oxidative stress in peripheral blood of both children and adults with CHD were reviewed. Different methods to assess the oxidant status were compared and divided into three categories: pro-oxidative or anti-oxidative stress markers and the ratio of pro-to-anti oxidative stress markers. This meta-analysis showed elevated oxidative stress levels in patients with CHD, and more specifically in patients with cCHD. Moreover, this indicates that there could be potential in oxidative stress measurements as a new biomarker of disease severity. Further research will be needed to clarify the exact role of oxidative stress and its contributors in CHD in order to get a better and more in-depth understanding of the underlying pathophysiology of CHD, especially the higher susceptibility of the right ventricle (RV) to progress to heart failure (HF). This could facilitate the development of antioxidant treatments and RV-specific HF therapies, which are necessary to improve survival in these patients and could be of particular importance in cCHD.

Circulating Reactive Oxygen Species in Adults with Congenital Heart Disease

Oxidative stress is an important pathophysiological mechanism in the development of numerous cardiovascular disorders, but few studies have examined the levels of oxidative stress in adults with congenital heart disease (CHD). The objective of this study was to investigate oxidative stress levels in adults with CHD and the association with inflammation, exercise capacity and endothelial function. To this end, 36 adults with different types of CHD and 36 age- and gender-matched healthy controls were enrolled. Blood cell counts, hs-CRP, NT-proBNP, fasting glucose, cholesterol levels, iron saturation and folic acid concentrations were determined in venous blood samples. Levels of superoxide anion radical in whole blood were determined using electron paramagnetic resonance spectroscopy in combination with the spin probe CMH. Physical activity was assessed with the IPAQ-SF questionnaire. Vascular function assessment (EndoPAT) and cardiopulmonary exercise testing were performed in the patient group. Superoxide anion radical levels were not statistically significantly different between adults with CHD and the matched controls. Moreover, oxidative stress did not correlate with inflammation, or with endothelial function or cardiorespiratory fitness in CHD; however, a significant negative correlation with iron saturation was observed. Overall, whole blood superoxide anion radical levels in adults with CHD were not elevated, but iron levels seem to play a more important role in oxidative stress mechanisms in CHD than in healthy controls. More research will be needed to improve our understanding of the underlying pathophysiology of CHD.

Definitions of low cardiac output syndrome after cardiac surgery and their effect on the incidence of intraoperative LCOS: A literature review and cohort study

Objectives

Low cardiac output syndrome (LCOS) is a serious complication after cardiac surgery. Despite scientific interest in LCOS, there is no uniform definition used in current research and clinicians cannot properly compare different study findings. We aimed to collect the LCOS definitions used in literature and subsequently applied the definitions obtained to existing data to estimate their effect on the intraoperative LCOS incidences in adults, children and infants.

Design

This is a literature review, followed by a retrospective cohort study.

Setting

This is a single-institutional study from a university hospital in the Netherlands.

Participants

Patients from all ages undergoing cardiac surgery with cardiopulmonary bypass between June 2011 and August 2018.

Interventions

We obtained different definitions of LCOS used in the literature and applied these to data obtained from an anesthesia information management system to estimate intraoperative incidences of LCOS. We compared intraoperative incidences of LCOS in different populations based on age (infants, children and adults).

Measurements and main results

The literature search identified 262 LCOS definitions, that were applied to intraoperative data from 7,366 patients. Using the 10 most frequently published LCOS definitions, the obtained incidence estimates ranged from 0.4 to 82% in infants, from 0.6 to 56% in children and from 1.5 to 91% in adults.

Conclusion

There is an important variety in definitions used to describe LCOS. When applied to data obtained from clinical care, these different definitions resulted in large distribution of intraoperative LCOS incidence rates. We therefore advocate for standardization of the LCOS definition to improve clinical understanding and enable adequate comparison of outcomes and treatment effects both in daily care and in research.

Oxidative Stress and Indicators of Brain Damage Following Pediatric Heart Surgery

Pediatric cardiac surgery induces an increased oxidative stress (OS) response. Increased OS is associated with poor neurologic outcomes in neonatal populations with similar patterns of brain injury. We investigated OS and brain injury in infants undergoing heart surgery. Patients 6 months or younger, undergoing cardiac surgery with or without cardiopulmonary bypass (CPB), were included in this prospective, observational study. Patients were divided into infant (30 days−6 months) and neonatal (<30 days) groups for analysis. Urine OS biomarker 8-iso-prostaglandin F2α (8-iso-PGF2α) was quantified pre-surgery and at 0 and 24 h post-surgery. A serum brain damage biomarker S100B protein was also measured pre-surgery and at 0 and 72 h post-surgery. Amplitude-integrated electroencephalography during surgery was analyzed. Neuropsychological evaluation using the Bayley III or Vineland test was performed in all patients at 24 months of age. Sixty-two patients were included, 44 of whom underwent follow-up neurologic evaluation. 8-iso-PGF2α and S100B levels were increased after surgery. Postoperative levels of S100B were positively correlated with 8-iso-PGF2α levels 24 h after surgery (rho = 0.5224; p = 0.0261). There was also a correlation between immediate post-surgery levels of 8-iso-PGF2α and intra-surgery seizure burden (rho = 0.4285, p = 0.0205). Patients with an abnormal neurological evaluation had increased levels of S100B 72 h after surgery (p = 0.048). 8-iso-PGF2α levels 24 h after surgery were also related to abnormal neurologic outcomes. Levels of 8-iso-PGF2α following pediatric cardiac surgery are associated with several indicators of brain injury including brain damage biomarkers, intra-operative seizures, and abnormal neurological evaluation at follow-up, suggesting the importance of oxidative stress response in the origin of brain damage in this population.

Riboflavin did not provide anti-inflammatory or antioxidant effects in an experimental model of sepsis

We aimed to evaluate whether the administration of riboflavin to septic animals reduces inflammation, oxidative stress, organ dysfunction, and mortality. C57BL/6 mice, 6-8 weeks old, were allocated to the study group (polymicrobial sepsis induced by cecal ligation and puncture (CLP) + antibiotic + iv riboflavin), control (CLP + antibiotic + iv saline), or naïve (non-operated controls). Serum concentrations of alanine aminotransferase (ALT), creatine kinase-MB (CK-MB), urea, and creatinine, and markers of inflammation [interleukin (IL)-6, tumor necrosis factor (TNF)-α, keratinocyte-derived chemokine (KC), and macrophage inflammatory protein (MIP)-2)], and oxidative stress (malondialdehyde (MDA) were measured 12 h after the experiment. Animal survival rates were calculated after 7 days. Means between groups were compared using linear regression models adjusted under the Bayesian approach. No significant difference was observed between control and study groups in serum concentrations of IL-6 (95% credible interval) (-0.35 to 0.44), TNF-α (-15.7 to 99.1), KC (-0.13 to 0.05), MIP-2 (-0.84 to 0.06), MDA (-1.25 to 2.53), or ALT (-6.6 to 11.5). Serum concentrations of CK-MB (-145.1 to -30.1), urea (-114.7 to -15.1), and creatinine (-1.14 to -0.01) were higher in the study group. Survival was similar in both groups (P=0.8). Therefore, the use of riboflavin in mice undergoing sepsis induced by CLP did not reduce inflammation, oxidative stress, organ dysfunction, or mortality compared with placebo.

Oxidative stress response in children undergoing cardiac surgery: Utility of the clearance of isoprostanes

INTRODUCTION

Cardiac surgery (CS) in pediatric patients induces an overt oxidative stress (OS) response. Children are particularly vulnerable to OS related injury. The immaturity of their organs and antioxidant systems as well as the induction of OS in cardio-pulmonary bypass (CPB) surgery may have an important impact on outcomes. The purpose of this study was to describe the OS response, measured by urinary free 8-iso-PGF2α, in infants undergoing CS and to evaluate the relationship between OS response and post-operative clinical outcomes.

METHODS

Infants with congenital heart disease undergoing CS with or without CPB were eligible for enrollment. Children were classified as neonates (<30 days) or infants (30 days-6 months) based on the age at surgery. Perioperative continuous non-invasive neuromonitoring included amplitude-integrated electroencephalogram and cerebral regional oxygen saturation measured with near-infrared spectroscopy. Urine 8-iso-PGF2α levels were measured before, immediately post-, and 24-hours post-surgery, and the 8-iso-PGF2 clearance was calculated.

RESULTS

Sixty-two patients (60% neonates) were included. Urine 8-iso-PGF2α levels 24 hours after surgery (8.04 [6.4-10.3] ng/mg Cr) were higher than pre-operative levels (5.7 [4.65-7.58] ng/mg Cr) (p<0.001). Those patients with a severe degree of cyanosis caused by Transposition of the Great Arteries (TGA) had the highest post-operative 8-iso-PGF2α levels. Patients with intra-operative seizures had higher post-operative 8-iso-PGF2α levels. 8-iso-PGF2α clearance at 24 hours post-surgery was different between newborns and infant patients, and it was inversely correlated with days of mechanical ventilation (p = 0.05), ICU LOS (p = 0.05) and VIS score at 24 hours (p = 0.036).

CONCLUSIONS

Children undergoing CS, particularly neonatal patients, experience a significant post-operative OS response that might play an important role in postoperative morbidity. TGA patients undergoing arterial switch operations demonstrate the highest post-operative OS response. Rapid clearance of isoprostanes, which occurs more frequently in older patients with more mature antioxidant systems, might be associated with better clinical outcomes.

Comparison of antioxidant reserve capacity of children with acyanotic & cyanotic congenital heart disease

Background & objectives:

Oxidative stress can cause many diseases and increases the risk of post-operative complications in children with congenital heart disease. For these reasons, this study was aimed to investigate the differences between cyanotic and acyanotic paediatric patients who underwent heart surgery with markers of oxidative stress.

Methods:

Eighty five patients were included in the study. The samples taken before the surgery and within the first 24 h after the surgery were evaluated for haemoglobin (Hb), leukocytes, uric acid, glutathione (GSH), malondialdehyde and total antioxidant capacity. Cyanotic, acyanotic, hyperoxygenated, normo-oxygenated, cardiac surgery with or without cardiopulmonary bypass (CPB) comparisons were made.

Results:

Positive correlation was found between age and pre-operative total antioxidant status values. Cyanotic and acyanotic patients did not have different antioxidant reserve capacities preoperatively. Although pre-operative thiobarbituric acid reactive substances (TBARS) levels were significantly lower in cyanotic patients, post-operative levels were higher. TBARS levels increased and GSH levels reduced postoperatively. The level of oxygenation did not cause a significant difference on markers of oxidative stress. The duration of CPB did not have negative effects on oxidative stress.

Interpretation & conclusions:

Cyanotic and younger patients were found to be more vulnerable to oxidative stress. The increased levels of TBARS and the decreased levels of GSH could be the indicators of oxidative damage depending on many factors such as surgery, CPB, ischaemia/reperfusion, inflammation, iron overload and oxygenation. The level of oxygenation does not cause a noticeable difference in oxidative stress. CPB causes oxidative stress, but if it is conducted appropriately, the duration of CPB does not cause a significant negative impact on oxidative stress.

Protein Carbonyl Content Is a Predictive Biomarker of Eccentric Left Ventricular Hypertrophy in Hemodialysis Patients

High prevalence of left ventricular hypertrophy (LVH) and elevated oxidative stress are associated with poor outcomes in chronic hemodialysis patients. Abnormal left ventriculаr geomеtry and different geometric patterns play an important role as well. Our study analyzed the role of oxidative stress on myocardial remodeling in these patients. Plasma malondialdehyde (MDA), protein carbonyl (PC) content, and total antioxidative capacity (TAC) were investigated in 104 hemodialysis patients together with transthoracic echocardiography. Compared to patients with normal ventricular geometry, patients with LVH had increased MDA and PC plasma concentration. Multivariate analysis demonstrated that protein carbonyls, as biomarkers of oxidative protein modification, were an independent predictor of eccentric hypertrophy (eLVH), including higher LV end-diastolic diameter and LV end-diastolic volume, (β = 0.32 and β = 0.28, p < 0.001 for both). The incidence of eLVH increased progressively from the lowest to the highest baseline PC tertile (p < 0.001 for the trend) and the subjects in the former group showed a 76% greater risk of developing eLVH compared to their counterparts. After further adjustment for the potential mediators, PCs carried eLVH odds (95% confidence interval (CI)) of 1.256 (0.998-1.514), per standard deviation increase. High plasma protein carbonyls levels are a significant independent predictor of eccentric LVH in chronic hemodialysis patients.

Circulating Concentrations of Redox Biomarkers Do Not Improve the Prediction of Adverse Cardiovascular Events in Patients With Type 2 Diabetes Mellitus

Background

Despite pathophysiological relevance and promising experimental data, the usefulness of biomarkers of oxidative stress for cardiac risk prediction is unclear. The aim of our study was to investigate the prognostic value of 6 biomarkers exploring different pathways of oxidative stress for predicting adverse cardiovascular outcomes in patients with type 2 diabetes mellitus beyond established risk factors.

Methods and Results

The SURDIAGENE (Survie, Diabete de type 2 et Genetique) prospective cohort study consecutively recruited 1468 patients with type 2 diabetes mellitus. Assays were performed at baseline, and incident cases of major adverse cardiovascular events (MACE)—first occurrence of cardiovascular death, nonfatal myocardial infarction, or stroke—were recorded during a median of 64 months. Advanced oxidation protein products, oxidative hemolysis inhibition assay, ischemia‐modified albumin, and total reductive capacity of plasma were not associated with the risk of MACE in univariate analyses. Fluorescent advanced glycation end products and carbonyls were associated with MACE (hazard ratio=1.38 per SD, 95% confidence interval 1.24‐1.54, P<0.001 and hazard ratio=1.15 per SD, 95% confidence interval 1.04‐1.27, P=0.006, respectively) in univariate analysis, but when added to a multivariate predictive model including traditional risk factors for MACE, these markers did not significantly improve c‐statistics or integrated discrimination index of the model.

Conclusions

These plasma concentrations of 6 markers, which cover a broad spectrum of oxidative processes, were not significantly associated with MACE occurrence and were not able to improve MACE risk discrimination and classification beyond classical risk factors in type 2 diabetes mellitus patients.

Antioxidant Therapeutic Strategies for Cardiovascular Conditions Associated with Oxidative Stress

Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability to scavenge these ROS by endogenous antioxidant systems, where ROS overwhelms the antioxidant capacity. Excessive presence of ROS results in irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Oxidative stress plays a crucial role in the pathogenesis of cardiovascular diseases related to hypoxia, cardiotoxicity and ischemia-reperfusion. Here, we describe the participation of OS in the pathophysiology of cardiovascular conditions such as myocardial infarction, anthracycline cardiotoxicity and congenital heart disease. This review focuses on the different clinical events where redox factors and OS are related to cardiovascular pathophysiology, giving to support for novel pharmacological therapies such as omega 3 fatty acids, non-selective betablockers and microRNAs.

Myocardial Oxidative Stress in Infants Undergoing Cardiac Surgery

Cardiac surgery for congenital heart disease often necessitates a period of myocardial ischemia during cardiopulmonary bypass and cardioplegic arrest, followed by reperfusion after aortic cross-clamp removal. In experimental models, myocardial ischemia-reperfusion is associated with significant oxidative stress and ventricular dysfunction. A prospective observational study was conducted in infants (<1 year) who underwent elective surgical repair of a ventricular septal defect (VSD) or tetralogy of Fallot (TOF). Blood samples were drawn following anesthetic induction (baseline) and directly from the coronary sinus at 1, 3, 5, and 10 min following aortic cross-clamp removal. Samples were analyzed for oxidant stress using assays for thiobarbituric acid-reactive substances, protein carbonyl, 8-isoprostane, and total antioxidant capacity. For each subject, raw assay data were normalized to individual baseline samples and expressed as fold-change from baseline. Results were compared using a one-sample t test with Bonferroni correction for multiple comparisons. Sixteen patients (ten with TOF and six with VSD) were enrolled in the study, and there were no major postoperative complications observed. For the entire cohort, there was an immediate, rapid increase in myocardial oxidative stress that was sustained for 10 min following aortic cross-clamp removal in all biomarker assays (all P < 0.01), except total antioxidant capacity. Infant cardiac surgery is associated with a rapid, robust, and time-dependent increase in myocardial oxidant stress as measured from the coronary sinus in vivo. Future studies with larger enrollment are necessary to assess any association between myocardial oxidative stress and early postoperative outcomes.

Oxidative Stress after Surgery on the Immature Heart

Paediatric heart surgery is associated with increased inflammation and the production of reactive oxygen species. Use of the extracorporeal cardiopulmonary bypass during correction of congenital heart defects generates reactive oxygen species by various mechanisms: haemolysis, neutrophil activation, ischaemia reperfusion injury, reoxygenation injury, or depletion of the endogenous antioxidants. The immature myocardium is more vulnerable to reactive oxygen species because of developmental differences compared to the adult heart but also because of associated congenital heart diseases that can deplete its antioxidant reserve. Oxidative stress can be manipulated by various interventions: exogenous antioxidants, use of steroids, cardioplegia, blood prime strategies, or miniaturisation of the cardiopulmonary bypass circuit. However, it is unclear if modulation of the redox pathways can alter clinical outcomes. Further studies powered to look at clinical outcomes are needed to define the role of oxidative stress in paediatric patients.

Right ventricular assist device with membrane oxygenator support for right ventricular failure following implantable left ventricular assist device placement

OBJECTIVES

Cardiogenic shock from refractory right ventricular (RV) failure during left ventricular assist device placement is associated with high morbidity and mortality. The addition of extracorporeal membrane oxygenation to RV mechanical assistance may help RV recovery and lead to improved outcomes.

METHODS

We retrospectively reviewed all implanted continuous-flow left ventricular assist devices from April 2009 to June 2013. RV mechanical support was utilized for RV failure defined as haemodynamic instability despite vasopressors, pulmonary vascular dilators and inotropic therapy. RV assist devices were utilized with and without in-line membrane oxygenation.

RESULTS

During the study period, 267 continuous-flow left ventricular assist devices were implanted. RV mechanical support was utilized in 27 (10%) patients; 12 (46%) had the addition of in-line extracorporeal membrane oxygenation. The mean age of patients with a right ventricular assist device with membrane oxygenation was lower than that in patients with a right ventricular assist device alone (45.6 ± 15.9 vs 64.6 ± 6.5, P = 0.001). Support was weaned in 66% (10 of 15) of patients with right ventricular assist device (RVAD) alone vs 83% (10 of 12) of those with RVAD with membrane oxygenation (P = 0.42). The RVAD was removed after 10.4 ± 9.4 vs 5 ± 2.99 days for patients with a RVAD with membrane oxygenation (P = 0.1). Patients with RVAD with membrane oxygenation had a 30-day mortality rate of 8 vs 47% for those with RVAD alone (P = 0.04). The survival rate after discharge was 86, 63 and 54% at 3, 6 and 12 months for both groups combined.

CONCLUSIONS

Patients with a RVAD with membrane oxygenation support for acute RV failure after continuous-flow left ventricular assist device implantation had a lower 30-day mortality than those with a RVAD alone. Patients who survive to discharge have a reasonable 1-year survival. Combining membrane oxygenation with RVAD support appears to offer a short-term survival benefit in patients with RV failure after continuous-flow left ventricular assist device implantation.