Ischemic myocardial injuries after cardiac malformation repair in infants may be associated with oxidative stress mechanisms

L-carnitine decreases myocardial injury in children undergoing open-heart surgery: A randomized controlled trial

Myocardial injury in open-heart surgery is related to several factors including ischemia-reperfusion injury, generation of reactive oxygen species, increased production of inflammatory mediators, and enhancement of apoptosis of cardiomyocytes. The aim of this study was to study the effect of L-carnitine on myocardial injury in children undergoing open-heart surgery. This clinical trial was performed on 60 children with congenital heart disease (CHD) who underwent open-heart surgery. They were randomized into two groups: L-carnitine group who received L-carnitine 50 mg\kg\day once daily for 1 month before cardiac surgery and control group who received placebo for 1 month before cardiac surgery. Left ventricular cardiac function was assessed by conventional echocardiography to measure left ventricular ejection fraction (LVEF) and two-dimensional speckle tracking echocardiography (2D-STE) to determine left ventricular global longitudinal strain (2D-LV GLS). Blood samples were obtained pre-operatively at baseline before the administration of L-carnitine or placebo and 12 h post-operatively to measure the level of malondialdehyde (MDA), superoxide dismutase (SOD), fas, caspase-3, creatinine kinase-MB (CK-MB), and troponin I. L-carnitine group had significantly lower post-operative level of oxidative stress marker (MDA), apoptosis markers (fas and caspase-3), and myocardial injury markers (CK-MB and troponin I), but they had significantly higher SOD post-operative level compared to the control group. In addition, post-operative LVEF and 2D-LVGLS were significantly lower in the control group compared to L-carnitine group.   Conclusion: L-carnitine can reduce myocardial injury, improve post-operative left ventricular cardiac function, and may provide myocardium protection in children with CHD who underwent open-heart surgery.   Trial registration: The clinical trial was registered at www.pactr.org with registration number PACTR202010570607420 at 29/10/2020 before recruiting the patients. What is Known: • Myocardial injury in open-heart surgery is related to several factors including ischemia-reperfusion injury, generation of reactive oxygen species, increased production of inflammatory mediators, and enhancement of apoptosis of cardiomyocytes. • L-carnitine was reported to have myocardial protective effects in rheumatic valvular surgery and coronary artery bypass graft (CABG) in adults; however, there is no evidence on its effectiveness in children undergoing open-heart surgery. What is New: • L-carnitine significantly lowered the post-operative level of oxidative stress marker (MDA), apoptosis markers (fas and caspase-3), and myocardial injury markers (CK-MB and troponin I) in the treatment group. • L-carnitine can reduce myocardial injury, improve post-operative left ventricular cardiac function, and may provide myocardium protection in children with CHD who underwent open-heart surgery.

Effect of different cardioprotective methods on extracorporeal circulation in fetal sheep: a randomized controlled trial

Background

Congenital heart disease is a leading cause of death in newborns and infants. The feasibility of fetal cardiac surgery is linked to extracorporeal circulation (ECC); therefore, cardioplegic solutions need to be effective and long-lasting.

Methods

Eighteen pregnant sheep were divided into an ECC-only group, St. Thomas’ Hospital cardioplegic solution (STH1) group (STH group), and HTK preservation solution (Custodiol®) group (HTK group). Markers of myocardial injury including troponin I (cTnI), troponin T (cTnT) and creatine kinase myocardial band (CKMB) were measured at specific time points (T1: pre-ECC, T2: 30 min of ECC, T3: 60 min of ECC, T4: 60 min post-ECC, T5: 120 min post-ECC). Myocardial tissue was removed from the fetal sheep at T5, and apoptosis was detected by TUNEL staining.

Results

Changes in the serum cTnI, cTnT and CKMB concentrations were not significantly different among the three groups before and during the ECC(T1,T2,T3). At 60 min after ECC shutdown(T4), cTnI and cTnT concentrations were significantly higher in the STH group than before the start of ECC. The concentration of cTnI was higher in the STH group than in the HTK and ECC-only groups. The concentration of cTnT was higher in the STH group than in the ECC-only group. At 120 min after ECC shutdown(T5), cTnI and cTnT concentrations were significantly higher in the ECC and HTK groups than before the start of ECC, and CKMB concentration was significantly higher in STH and HTK groups. The concentrations of cTnT, cTnI and CKMB was higher in the STH group than in the HTK and ECC-only groups. The number of TUNEL-positive cells in the HTK and STH groups was higher than in the ECC-only group. The number of TUNEL-positive cells in the STH group was higher than in the HTK group. There was no statistically significant difference among the groups in the heart rate and mean arterial pressure after ECC.

Conclusion

The HTK preservation solution was significantly better than STH1 in reducing the release of cardiomyocyte injury markers and the number of apoptotic cells in fetal sheep ECC. Fetal sheep receiving ECC-only had an advantage in all indicators, which suggests ECC-only fetal heart surgery is feasible.

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.

Increased Atrial β-Adrenergic Receptors and GRK-2 Gene Expression Can Play a Fundamental Role in Heart Failure After Repair of Congenital Heart Disease with Cardiopulmonary Bypass

Surgeries to correct congenital heart diseases are increasing in Brazil and worldwide. However, even with the advances in surgical techniques and perfusion, some cases, especially the more complex ones, can develop heart failure and death. A retrospective study of patients who underwent surgery for correction of congenital heart diseases with cardiopulmonary bypass (CPB) in a university tertiary-care hospital that died, showed infarction in different stages of evolution and scattered microcalcifications in the myocardium, even without coronary obstruction. CPB is a process routinely used during cardiac surgery for congenital heart disease. However, CPB has been related to increased endogenous catecholamines that can lead to major injuries in cardiomyocytes. The mechanisms involved are not completely understood. The aim of this study was to evaluate the alterations induced in the β-adrenergic receptors and GRK-2 present in atrial cardiomyocytes of infants with congenital heart disease undergoing surgical repair with CPB and correlate the alterations with functional and biochemical markers of ischemia/myocardial injury. The study consisted of right atrial biopsies of infants undergoing surgical correction in HC-FMRPUSP. Thirty-three cases were selected. Atrial biopsies were obtained at the beginning of CPB (group G1) and at the end of CPB (group G2). Real-time PCR, Western blotting, and immunofluorescence analysis were conducted to evaluate the expression of β₁, β₂-adrenergic receptors, and GRK-2 in atrial myocardium. Cardiac function was evaluated by echocardiography and biochemical analysis (N-terminal pro-brain natriuretic peptide (NT-ProBNP), lactate, and cardiac troponin I). We observed an increase in serum lactate, NT-proBNP, and troponin I at the end of CPB indicating tissue hypoxia/ischemia. Even without major clinical consequences in cardiac function, these alterations were followed by a significant increase in gene expression of β₁ and β₂ receptors and GRK-2, suggesting that this is one of the mechanisms responsible for the exacerbated response of cardiomyocytes to circulating catecholamines. These alterations could explain the irreversible myocardial damage and lipid peroxidation of membranes classically attributed to catecholamine excess, observed in some infants who develop heart failure and postoperative death. Although other factors may be involved, this study confirms that CPB acts as a potent inducer of increased gene expression of β- adrenergic receptors and GRK-2, making the myocardium of these infants more susceptible to the effects of circulating endogenous catecholamines, which may contribute to the development of irreversible myocardial damage and death.

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.

Histidine-tryptophan-ketoglutarate solution with added ebselen augments myocardial protection in neonatal porcine hearts undergoing ischemia/reperfusion

Whether modified histidine-tryptophan-ketoglutarate (HTK) solution offers myocardial protection to newborn heart has not been documented. The purpose of this study was to compare myocardial protection using HTK added by ebselen with HTK in a piglet model of cardiopulmonary bypass (CPB). Fifteen piglets were randomly assigned to three groups: the control group (C group, n = 5), HTK solution group (HTK group, n = 5), and HTK added by 10 nM ebselen group (HTK+E group, n = 5). Animals in the two experimental groups were placed on hypothermic CPB, after which the ascending aorta had been clamped for 2 h. The control animals underwent normothermic CPB without cardiac arrest. Myocardial antioxidant activities, myocytes apoptosis and mitochondrial structures, as well as the release of cytochrome c and the expression of Bax, Bcl-2, and HSP72 protein in myocardium were measured. Increased myocardial superoxide dismutase (SOD) and Mn-SOD activities, decreased TUNEL-positive cells, and reduced release of cytochrome c were noted in the HTK+E group compared with those in the HTK group (P = 0.021, P = 0.020, P = 0.045, and P = 0.010, respectively). The Bax/Bcl-2 ratio in the HTK group was significantly higher than that in the C group (P = 0.024). The expression of HSP72 protein and mRNA in the HTK+E group was higher than that in the HTK group (P = 0.039 and P = 0.035, respectively). Mitochondrial score under electron microscope in the HTK+E group was lower than that in the HTK group (P = 0.047). Improved antioxidant defense, reduced myocytes apoptosis, and better preserved mitochondrial structure were observed in the HTK+E group. Ebselen added to HTK provides better myocardioprotection to HTK solution for the neonatal heart.

The proper delivery pressure for cardioplegic solution in neonatal cardiac surgery - an investigation of biomechanical and structural properties of neonatal and adult coronary arteries

When cardioplegic solution is injected into coronary arteries with a pump in order to ensure myocardial protection, it is necessary to determine the correct delivery pressure to avoid damage of the heart. Biomechanical and structural properties of the neonatal coronary artery wall should be taken into account when determining the delivery pressure. We investigated twelve coronary artery specimens without cardiac pathology retrieved from autopsies of neonates 9.3 ± 9.7 days old and compared them to adult specimens with no detected atherosclerosis. There was a rapid increase in the strain until the inner pressure reached 80 - 100 mmHg, whilst the increase of stress in the wall of the neonatal coronary arteries was less rapid. When the pressure exceeded 100 mmHg, the increase in the strain slowed down, whilst the wall stress and modulus of elasticity began to increase rapidly. Morphologic examination of tensile properties revealed prominent affection of the vascular wall of the neonates, with accentuated redistribution (loosening) of medial myocytes and the adventitial vasa vasorum. Collectively, a raised inner pressure applied to cardioplegic solution injected into the coronary artery of a neonate may increase the risk of structural damage to the vascular wall.

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

OBJECTIVES

To investigate whether perioperative serum levels of oxidative stress markers, thiobarbituric acid reactive substances (TBARS), and carbonyl moieties are associated with outcomes in children after heart surgery.

BACKGROUND

Oxidative stress markers are increased following heart surgery with cardiopulmonary bypass (CPB) and can play a role in ischemia-reperfusion injury, but its associations with myocardial dysfunction, low cardiac output syndrome (LCOS), and outcomes are not proven.

METHODS

In a retrospective secondary analysis of a cohort study comprising 55 children (median age, 109 [2-611] days), we compared pre-, intra- and postoperative serum levels of TBARS and carbonyl moieties among patients with and without postoperative LCOS, cyanotic and acyanotic congenital heart disease (CHD), and survivors and nonsurvivors. We also assessed the independent effect of TBARS and carbonyl moieties peak levels on the mortality-adjusted hospital length of stay (aLOS).

RESULTS

Patients who developed postoperative LCOS (n = 36) were significantly younger, more frequently cyanotic, more severely ill, and underwent more complex procedures with longer CPB. However, TBARS and carbonyl moieties serum levels did not change significantly over time. Moreover, they were not significantly different in patients with or without LCOS, cyanotic and acyanotic CHD, or survivors and nonsurvivors. There was a significant correlation between TBARS and tumor necrosis factor alpha (TNF-α) peak serum levels. Neither TBARS nor carbonyl moieties peak serum levels were independently associated with aLOS.

CONCLUSIONS

In conclusion, oxidative stress markers TBARS and carbonyl moieties were not associated with the development of LCOS, the aLOS, or mortality in children after heart surgery with CPB.

Calcified myocardial necrosis in pediatric patients after cardiopulmonary resuscitation

We report three autopsy cases of wide-spread myocardial necrosis with calcification in pediatric patients after temporary generalized hypoxia and initially successful cardiopulmonary resuscitation, but subsequent in-hospital death. Autopsy and histological workup in all three cases showed multiple circumscribed calcified and necrotic areas in progressive stages of organization within the myocardium. We conclude that these macro- and microscopic autopsy features appear to be related to reperfusion injuries in children as a consequence of hypoxic-ischemic changes occurring in the peri- and postresuscitation period.

Impact of N-acetylcysteine on neonatal cardiomyocyte ischemia-reperfusion injury

Reactive oxygen species (ROS) are hypothesized to play a key role in myocardial ischemia-reperfusion (IR) injury after cardiopulmonary bypass in children. Clinical studies in adults and several animal models suggest that myocardial IR injury involves cardiomyocyte apoptosis and necrosis. This study investigated a potential relationship between IR-induced ROS production and neonatal cardiomyocyte apoptosis using both in vitro and ex vivo techniques. For in vitro experiments, embryonic rat cardiomyocytes (H9c2 cells) exposed to hypoxia-reoxygenation (HR) showed a time-dependent increase in gp91 phox (a marker for ROS production by NADPH oxidases), caspase-3 (a key mediator of apoptosis) expression, and a decrease in the glutathione redox ratio. N-acetylcysteine (NAC; 0.25-2 mM), a potent antioxidant, decreased gp91 phox and caspase-3 expression, inhibited apoptosis and restored the glutathione redox ratio. For ex vivo study, IR injury significantly reduced left ventricular (LV) function and increased the expression of gp91 phox and caspase-3 in Langendorff-perfused neonatal (7-14 d) rabbit hearts. NAC (0.4 mM) treatment completely attenuated LV dysfunction after IR. In summary, neonatal myocardial IR injury is associated with an increase in cardiomyocyte oxidative stress and apoptosis. NAC attenuates apoptosis in an in vitro embryonic rat cardiomyocyte model of HR, and myocardial dysfunction in an ex vivo neonatal rabbit model of myocardial IR injury.

Cardiac beriberi: morphological findings in two fatal cases

Cardiovascular beriberi is categorized into two main groups, according to its cause: alcoholic and non-alcoholic (dietary). Cardiovascular beriberi can also be divided into a fulminant form (Shoshin beriberi) and a chronic form. Shoshin beriberi is characterized by hypotension, tachycardia, and lactic acidosis and is mainly encountered in non-alcoholic patients in Asian countries, although it has also been seen in alcoholics in Western countries. Due to the complex clinical presentation and to the lack of diagnostic tests, thiamine deficiency is still being missed, especially among non-alcoholics patients. We present two fatal cases of non - alcohol associated cardiac beriberi. An acute myocardial infarction was observed in one case; extensive colliquative myocytolisis (grade 2) was described in the second case respectively. Morphologically, myocardial necrosis and colliquative myocytolysis are the histologic hallmarks of this acute, rare clinical entity. An increase in apoptotic myocytes was demonstrated probably sustaining the cardiogenic shock.