Oxidative Stress Biomarkers and Incidence of Postoperative Atrial Fibrillation in the Omega-3 Fatty Acids for Prevention of Postoperative Atrial Fibrillation (OPERA) Trial

Hereditary hemochromatosis with homozygous C282Y HFE mutation: possible clinical model to assess effects of elevated reactive oxygen species on the development of cardiovascular disease

Hereditary hemochromatosis with the homozygous C282Y HFE mutation (HH-282H) is a genetic condition which causes iron overload (IO) and elevated reactive oxygen species (ROS) secondary to the IO. Interestingly, even after successful iron removal therapy, HH-282H subjects demonstrate chronically elevated ROS. Raised ROS are also associated with the development of multiple cardiovascular diseases and HH-282H subjects may be at risk to develop these complications. In this narrative review, we consider HH-282H subjects as a clinical model for assessing the contribution of elevated ROS to the development of cardiovascular diseases in subjects with fewer confounding clinical risk factors as compared to other disease conditions with high ROS. We identify HH-282H subjects as a potentially unique clinical model to assess the impact of chronically elevated ROS on the development of cardiovascular disease and to serve as a clinical model to detect effective interventions for anti-ROS therapy.

NADPH Oxidases and Oxidative Stress in the Pathogenesis of Atrial Fibrillation

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and its prevalence increases with age. The irregular and rapid contraction of the atria can lead to ineffective blood pumping, local blood stasis, blood clots, ischemic stroke, and heart failure. NADPH oxidases (NOX) and mitochondria are the main sources of reactive oxygen species in the heart, and dysregulated activation of NOX and mitochondrial dysfunction are associated with AF pathogenesis. NOX- and mitochondria-derived oxidative stress contribute to the onset of paroxysmal AF by inducing electrophysiological changes in atrial myocytes and structural remodeling in the atria. Because high atrial activity causes cardiac myocytes to expend extremely high energy to maintain excitation-contraction coupling during persistent AF, mitochondria, the primary energy source, undergo metabolic stress, affecting their morphology, Ca2+ handling, and ATP generation. In this review, we discuss the role of oxidative stress in activating AF-triggered activities, regulating intracellular Ca2+ handling, and functional and anatomical reentry mechanisms, all of which are associated with AF initiation, perpetuation, and progression. Changes in the extracellular matrix, inflammation, ion channel expression and function, myofibril structure, and mitochondrial function occur during the early transitional stages of AF, opening a window of opportunity to target NOX and mitochondria-derived oxidative stress using isoform-specific NOX inhibitors and mitochondrial ROS scavengers, as well as drugs that improve mitochondrial dynamics and metabolism to treat persistent AF and its transition to permanent AF.

The Role of Major Biomarkers of Stress in Atrial Fibrillation: A Literature Review

Numerous studies have reported that physical or emotional stress can provoke atrial fibrillation (AF) or vice versa, which suggests a potential link between exposure to external stressors and AF. This review article sought to describe in detail the relationship between major stress biomarkers and the pathogenesis of AF and presents up-to-date knowledge on the role of physiological and psychological stress in AF patients. For this purpose, this review article contends that plasma cortisol is linked to a greater risk of AF. A previous study has investigated the association between increased copeptin levels and paroxysmal AF (PAF) in rheumatic mitral stenosis and reported that copeptin concentration was not independently associated with AF duration. Reduced levels of chromogranin were measured in patients with AF. Furthermore, the dynamic activity of antioxidant enzymes, including catalase as well as superoxide dismutase, was examined in PAF patients during a period of <48 h. Malondialdehyde activity, serum high-sensitivity C-reactive protein, and high mobility group box 1 protein concentrations were significantly greater in patients with persistent AF or PAF compared to controls. Pooled data from 13 studies confirmed a significant reduction in the risk of AF related to the administration of vasopressin. Other studies have revealed the mechanism of action of heat shock proteins (HSPs) in preventing AF and also discussed the therapeutic potential of HSP-inducing compounds in clinical AF. More research is required to detect other biomarkers of stress, which have not been reported in the pathogenesis of AF. Further studies are required to identify their mechanism of action and drugs to manage these biomarkers of stress in AF patients, which might help to reduce the prevalence of AF globally.

Dynamic Plasma Lipidomic Analysis Revealed Cholesterol Ester and Amides Associated with Sepsis Development in Critically Ill Patients after Cardiovascular Surgery with Cardiopulmonary Bypass

Background: Sepsis in patients after cardiovascular surgery with cardiopulmonary bypass (CPB) has a high rate of mortality. We sought to determine whether changes in lipidomics can predict sepsis after cardiac surgery. Methods: We used high-performance liquid chromatography coupled to tandem mass spectrometry to explore global lipidome changes in samples from a prospective case-control cohort (30 sepsis vs. 30 nonsepsis) hospitalized with cardiovascular surgery. All patients were sampled before and within 48−72 h after surgery. A bioinformatic pipeline was applied to acquire reliable features and MS/MS-driven identifications. Furthermore, a multiple-step machine learning framework was performed for signature discovery and performance evaluation. Results: Compared with preoperative samples, 94 features were upregulated and 282 features were downregulated in the postoperative samples of the sepsis group, and 73 features were upregulated and 265 features were downregulated in the postoperative samples of the nonsepsis group. “Autophagy”, “pathogenic Escherichia coli infection” and “glycosylphosphatidylinositol-anchor biosynthesis” pathways were significantly enriched in the pathway enrichment analysis. A multistep machine learning framework further confirmed that two cholesterol esters, CE (18:0) and CE (16:0), were significantly decreased in the sepsis group (p < 0.05). In addition, oleamide and stearamide were increased significantly in the postoperative sepsis group (p < 0.001). Conclusions: This study revealed characteristic lipidomic changes in the plasma of septic patients before and after cardiac surgery with CPB. We discovered two cholesterol esters and two amides from peripheral blood that could be promising signatures for sepsis within a dynamic detection between the preoperative and postoperative groups.

Impact of obesity on post-operative arrhythmias after congenital heart surgery in children and young adults

BACKGROUND

Obesity increases the risk of post-operative arrhythmias in adults undergoing cardiac surgery, but little is known regarding the impact of obesity on post-operative arrhythmias after CHD surgery.

METHODS

Patients undergoing CHD surgery from 2007 to 2019 were prospectively enrolled in the parent study. Telemetry was assessed daily, with documentation of all arrhythmias. Patients aged 2-20 years were categorised by body mass index percentile for age and sex (underweight <5, normal 5-85, overweight 85-95, and obese >95). Patients aged >20 years were categorised using absolute body mass index. We investigated the impact of body mass index category on arrhythmias using univariate and multivariate analysis.

RESULTS

There were 1250 operative cases: 12% underweight, 65% normal weight, 12% overweight, and 11% obese. Post-operative arrhythmias were observed in 38%. Body mass index was significantly higher in those with arrhythmias (18.8 versus 17.8, p = 0.003). There was a linear relationship between body mass index category and incidence of arrhythmias: underweight 33%, normal 38%, overweight 42%, and obese 45% (p = 0.017 for trend). In multivariate analysis, body mass index category was independently associated with post-operative arrhythmias (p = 0.021), with odds ratio 1.64 in obese patients as compared to normal-weight patients (p = 0.036). In addition, aortic cross-clamp time (OR 1.007, p = 0.002) and maximal vasoactive-inotropic score in the first 48 hours (OR 1.03, p = 0.04) were associated with post-operative arrhythmias.

CONCLUSION

Body mass index is independently associated with incidence of post-operative arrhythmias in children after CHD surgery.

Amiodarone with or without N-Acetylcysteine for the Prevention of Atrial Fibrillation after Thoracic Surgery: A Double-blind, Randomized Trial

BACKGROUND

Postoperative atrial fibrillation may identify patients at risk of subsequent atrial fibrillation, with its greater risk of stroke. This study hypothesized that N-acetylcysteine mitigates inflammation and oxidative stress to reduce the incidence of postoperative atrial fibrillation.

METHODS

In this double-blind, placebo-controlled trial, patients at high risk of postoperative atrial fibrillation scheduled to undergo major thoracic surgery were randomized to N-acetylcysteine plus amiodarone or placebo plus amiodarone. On arrival to the postanesthesia care unit, N-acetylcysteine or placebo intravenous bolus (50 mg/kg) and then continuous infusion (100 mg/kg over the course of 48 h) was administered plus intravenous amiodarone (bolus of 150 mg and then continuous infusion of 2 g over the course of 48 h). The primary outcome was sustained atrial fibrillation longer than 30 s by telemetry (first 72 h) or symptoms requiring intervention and confirmed by electrocardiography within 7 days of surgery. Systemic markers of inflammation (interleukin-6, interleukin-8, tumor necrosis factor α, C-reactive protein) and oxidative stress (F2-isoprostane prostaglandin F2α; isofuran) were assessed immediately after surgery and on postoperative day 2. Patients were telephoned monthly to assess the occurrence of atrial fibrillation in the first year.

RESULTS

Among 154 patients included, postoperative atrial fibrillation occurred in 15 of 78 who received N-acetylcysteine (19%) and 13 of 76 who received placebo (17%; odds ratio, 1.24; 95.1% CI, 0.53 to 2.88; P = 0.615). The trial was stopped at the interim analysis because of futility. Of the 28 patients with postoperative atrial fibrillation, 3 (11%) were discharged in atrial fibrillation. Regardless of treatment at 1 yr, 7 of 28 patients with postoperative atrial fibrillation (25%) had recurrent episodes of atrial fibrillation. Inflammatory and oxidative stress markers were similar between groups.

CONCLUSIONS

Dual therapy comprising N-acetylcysteine plus amiodarone did not reduce the incidence of postoperative atrial fibrillation or markers of inflammation and oxidative stress early after major thoracic surgery, compared with amiodarone alone. Recurrent atrial fibrillation episodes are common among patients with postoperative atrial fibrillation within 1 yr of major thoracic surgery.

EDITOR’S PERSPECTIVE

A Genotype-Phenotype Analysis of Glutathione Peroxidase 4 in Human Atrial Myocardium and Its Association with Postoperative Atrial Fibrillation

Heterogeneity in the incidence of postoperative atrial fibrillation (POAF) following heart surgery implies that underlying genetic and/or physiological factors impart a higher risk of this complication to certain patients. Glutathione peroxidase-4 (GPx4) is a vital selenoenzyme responsible for neutralizing lipid peroxides, mediators of oxidative stress known to contribute to postoperative arrhythmogenesis. Here, we sought to determine whether GPX4 single nucleotide variants are associated with POAF, and whether any of these variants are linked with altered GPX4 enzyme content or activity in myocardial tissue. Sequencing analysis was performed across the GPX4 coding region within chromosome 19 from a cohort of patients (N = 189) undergoing elective coronary artery bypass graft (−/+ valve) surgery. GPx4 enzyme content and activity were also analyzed in matching samples of atrial myocardium from these patients. Incidence of POAF was 25% in this cohort. Five GPX4 variants were associated with POAF risk (permutated p ≤ 0.05), and eight variants associated with altered myocardial GPx4 content and activity (p < 0.05). One of these variants (rs713041) is a well-known modifier of cardiovascular disease risk. Collectively, these findings suggest GPX4 variants are potential risk modifiers and/or predictors of POAF. Moreover, they illustrate a genotype−phenotype link with this selenoenzyme, which will inform future mechanistic studies.

Incidence and Outcomes of Postoperative Atrial Fibrillation after Coronary Artery Bypass Grafting of a Randomized Controlled Trial: A Blinded End-of-cycle Analysis

Objective

The objective of this study is to analyse the incidence of postoperative atrial fibrillation (POAF), demography, post-operative outcomes including morbidity and mortality, length of Cardiac Intensive Care Unit (CICU) stay, High Dependency Unit (HDU) stay, and total hospital stay in patients undergoing coronary bypass grafting (CABG) at Institut Jantung Negana (IJN).

Methods

We conducted a prospective, randomised, controlled trial. We supplied the treatment group with Tocovid capsules and the control group with placebo containing palm superolein.

Results

Since January 2019, we have recruited the target population of 250 patients. However, the result is still blinded as we are still analysing blood samples for tocotrienol levels. 89.2% of patients completed the study with a 3.6% mortality and a 7.6% attrition rate. 35.2% of the patients developed POAF, the mean time being 46.06 ± 26.96 hours post-CABG. We did not observe any statistically significant difference when we compared left atrial size, New York Heart Association (NYHA) functional class, ejection fraction and premorbid history, besides EuroSCORE II (The European System for Cardiac Operative Risk Evaluation II) status except for older age group, right atrial size, and pleural effusion. There was also no difference in bypass time, cross clamp time or number of anastomoses. However, we noted a significant difference in death (p = 0.01) and renal failure requiring dialysis (p = 0.007) among patients with POAF; those patients also had a longer CICU stay (p = 0.005), HDU stay (p = 0.02), and total hospital stay (p = 0.001).

Conclusions

POAF is associated with a higher incidence of renal failure and death while it increases CICU, HDU, and total hospital stay. It remains to be seen whether Tocovid reduces POAF and its associated sequelae.

Clinical Trial Registration

NCT03807037 (Registered on 16 January 2019).

The effect of nanocurcumin on the incidence of atrial fibrillation, and markers of inflammation and oxidative stress level after coronary artery bypass graft surgery: A randomized, double-blind, placebo-controlled clinical study

Objective

Postoperative atrial fibrillation (POAF) is the most frequent dysrhythmias observed following coronary artery bypass graft (CABG) surgery. Several studies have shown the beneficial effects of curcumin on cardiovascular diseases; however, there is no clinical trial to examine its effect on POAF. This randomized, double-blind, placebo-controlled clinical study was designed to evaluate the prophylactic effects of a nano-formulation of curcumin (SinaCurcumin™) versus placebo on POAF and levels of biomarkers of inflammation and oxidative stress in patients undergoing CABG surgery.

Materials and Methods

A total of 234 eligible patients were randomized to receive 240 mg curcumin nano-formulation or placebo three days prior to the surgery and on the first four postoperative days. The occurrence of POAF was monitored for at least 96 hr after the surgery. Also, C-reactive protein (hs-CRP), malondialdehyde (MDA) and glutathione (GSH) levels were assessed at baseline and the end of the study.

Results

Analyses were done in the intention-to-treat population. No significant difference was observed in the occurrence of POAF between the treatment (9.5%) and placebo (11.5%) groups. Also, curcumin intervention did not alter serum concentration of the hs-CRP, MDA, or GSH in comparison with placebo.

Conclusion

In conclusion, it seems that perioperative treatment with SinaCurcumin™ did not prevent POAF after CABG surgery.

Anesthesia-Induced Oxidative Stress: Are There Differences between Intravenous and Inhaled Anesthetics?

Agents used for the induction of anesthesia have been shown to either promote or mitigate oxidative stress. A fine balance between the presence of reactive oxygen species (ROS) and antioxidants is crucial for the proper normal functioning of the cell. A basal concentration of ROS is essential for the manifestation of cellular functions, whereas disproportionate levels of ROS cause damage to cellular macromolecules such as DNA, lipids, and proteins, eventually leading to necrosis and apoptosis. Increased ROS has been linked with numerous illnesses, such as cardiovascular, immune system, liver, and kidney, and has been shown to promote cancer and accelerate aging. Knowledge of the various pharmacologic agents that increase or reduce oxidative stress may promote a safer way of inducing anesthesia. Furthermore, surgery itself leads to increased ROS production and ischemia/reperfusion injury. Indeed, increased perioperative oxidative stress has been correlated with increased postoperative complications and prolonged recovery. Anesthesiologists care for patients during the whole spectrum of perioperative care and thus are in a unique position to deliver countermeasures to oxidative stress. Using preferentially an induction agent which reduces oxidative stress might lead to better clinical outcomes and fewer postoperative complications. Propofol has been shown in several studies to reduce oxidative stress, which reduces postoperative complications and leads to a faster recovery, and thus might represent the preferred induction agent in the right clinical setting.

Novel Combined Antioxidant Strategy against Hypertension, Acute Myocardial Infarction and Postoperative Atrial Fibrillation

Reactive oxygen species (ROS) play a physiological role in the modulation of several functions of the vascular wall; however, increased ROS have detrimental effects. Hence, oxidative stress has pathophysiological impacts on the control of the vascular tone and cardiac functions. Recent experimental studies reported the involvement of increased ROS in the mechanism of hypertension, as this disorder associates with increased production of pro-oxidants and decreased bioavailability of antioxidants. In addition, increased ROS exposure is found in ischemia-reperfusion, occurring in acute myocardial infarction and cardiac surgery with extracorporeal circulation, among other settings. Although these effects cause major heart damage, at present, there is no available treatment. Therefore, it should be expected that antioxidants counteract the oxidative processes, thereby being suitable against cardiovascular disease. Nevertheless, although numerous experimental studies agree with this notion, interventional trials have provided mixed results. A better knowledge of ROS modulation and their specific interaction with the molecular targets should contribute to the development of novel multitarget antioxidant effective therapeutic strategies. The complex multifactorial nature of hypertension, acute myocardial infarction, and postoperative atrial fibrillation needs a multitarget antioxidant strategy, which may give rise to additive or synergic protective effects to achieve optimal cardioprotection.

The Role of microRNAs in Metabolic Syndrome-Related Oxidative Stress

Oxidative stress (OxS) is the cause and the consequence of metabolic syndrome (MetS), the incidence and economic burden of which is increasing each year. OxS triggers the dysregulation of signaling pathways associated with metabolism and epigenetics, including microRNAs, which are biomarkers of metabolic disorders. In this review, we aimed to summarize the current knowledge regarding the interplay between microRNAs and OxS in MetS and its components. We searched PubMed and Google Scholar to summarize the most relevant studies. Collected data suggested that different sources of OxS (e.g., hyperglycemia, insulin resistance (IR), hyperlipidemia, obesity, proinflammatory cytokines) change the expression of numerous microRNAs in organs involved in the regulation of glucose and lipid metabolism and endothelium. Dysregulated microRNAs either directly or indirectly affect the expression and/or activity of molecules of antioxidative signaling pathways (SIRT1, FOXOs, Keap1/Nrf2) along with effector enzymes (e.g., GPx-1, SOD1/2, HO-1), ROS producers (e.g., NOX4/5), as well as genes of numerous signaling pathways connected with inflammation, insulin sensitivity, and lipid metabolism, thus promoting the progression of metabolic imbalance. MicroRNAs appear to be important epigenetic modifiers in managing the delicate redox balance, mediating either pro- or antioxidant biological impacts. Summarizing, microRNAs may be promising therapeutic targets in ameliorating the repercussions of OxS in MetS.

Lipid Profile Modulates Cardiometabolic Risk Biomarkers Including Hypertension in People with Type-2 Diabetes: A Focus on Unbalanced Ratio of Plasma Polyunsaturated/Saturated Fatty Acids

Type 2 diabetes mellitus (T2DM) is associated with lipid metabolism disorder, particularly elevated plasma levels of non-esterified free fatty acids (NEFFA) and an increased cardiovascular disease risk, such as essential hypertension (H). The plasma unbalance of saturated fatty acid (SFA)/polyunsaturated fatty acid (PUFA) ratio is a likely contributor, but the mechanisms involved are not clearly elucidated. The aim of this study is to explore the association between plasma SFA/PUFA ratio and the clusters of cardiometabolic syndrome (CMS), including the atherogenic biomarkers, inflammatory status, feeding patterns, and physical activity in people with T2DM with or without essential hypertension. The study was conducted on 784 adult male and female participants, aged between 30 and 50 years, and divided into 3 groups: 100 T2DM without hypertension (D); 368 T2DM with hypertension (DM); and 316 hypertensive participants without T2DM (H). All Participants were phenotyped regarding CMS clusters according to the NCEP/ATPIII criteria. Insulin resistance was assessed by Homeostasis model assessment (HOMA model). Metabolic, atherogenic, and inflammatory parameters were analyzed by biochemical methods; NEFFA by microfluorimetry; SFA, PUFA-n6 and PUFA-n3 by gas phase chromatography. Dietary lipids and physical activity were analyzed through the use of validated questionnaires. The clusters of CMS were found in all groups. Dyslipidemia was correlated with accretion NEFFA levels in all groups, but more accentuated in the DH group (r = +0.77; p < 0.001). Similarly, plasma PUFA/SFA ratio and PUFA-3 level was lower, concomitantly with a higher plasma ApoB100/ApoA1 (p < 0.001), lipoprotein (a), homocysteine (p < 0.001), and pro-inflammatory cytokines (TNFα, IL-6, IL1-β) in the DH group. Likewise, the depletion of PUFA-n3/PUFA-n6 ratio is associated with the decrease of omega 3-DHA (docosahexaenoic acid) and omega 3-EPA (eicosapentaenoic acid) (p < 0.001). It appears that the PUFAs-n3 ratio modulates cardiometabolic risk, inflammatory state and atherogenic biomarkers. The plasma unbalanced ratio of SFA/PUFA reflects dietary fatty acids intake. The contribution of dietary lipids is undisputed. Nutritional recommendations are required to determine the fatty acids ratio (saturated and unsaturated) provided in the diet.

Comparative effectiveness of allopurinol and febuxostat for the risk of atrial fibrillation in the elderly: a propensity-matched analysis of Medicare claims data

AIMS

Gout is associated with a higher risk of atrial fibrillation (AF). Comparative effectiveness of allopurinol or febuxostat for reducing the AF risk is unknown, which was our study's main objective.

METHODS AND RESULTS

We used the 5% Medicare Beneficiary cohort (≥65 years) from 2006 to 2012 to identify people with a new filled prescription for allopurinol or febuxostat, with a baseline period of 365 days without respective medication and without AF. We used 5:1 propensity-matched Cox regression analyses to assess whether allopurinol use differed from febuxostat use regarding the hazard ratio (HR) of incident AF. We found 25 732 eligible episodes in 23 135 beneficiaries. Of these, 2311 incident allopurinol or febuxostat use episodes (9%) ended in incident AF with crude incidence rates of 8.0 and 10.5 per 100 person-years, respectively. In propensity-matched analyses, compared with allopurinol, febuxostat was associated with higher HR of AF, 1.25 [95% confidence interval (CI) 1.05-1.48]. Compared with allopurinol <200 mg/day, febuxostat 80 mg/day was associated with significantly higher HR of AF, 1.62 (95% CI 1.16-2.27), but not febuxostat 40 mg/day or higher allopurinol doses. Compared with 1-180 days of allopurinol use, febuxostat use for 1-180 days was associated with significantly higher HR of AF, 1.36 (95% CI 1.10-1.67), but longer durations were not.

CONCLUSION

Febuxostat was associated with a higher risk of AF compared with allopurinol in older adults. Increased AF risk was noted with febuxostat 80 mg/day dose and was most evident in the first 6 months of use. These findings need replication.

Prospective Evaluation of Clinico-Pathological Predictors of Postoperative Atrial Fibrillation: An Ancillary Study From the OPERA Trial

BACKGROUND

Postoperative atrial fibrillation (POAF) occurs in 30% to 50% of patients undergoing cardiac surgery and is associated with increased morbidity and mortality. Prospective identification of structural/molecular changes in atrial myocardium that correlate with myocardial injury and precede and predict risk of POAF may identify new molecular pathways and targets for prevention of this common morbid complication.

METHODS

Right atrial appendage samples were prospectively collected during cardiac surgery from 239 patients enrolled in the OPERA trial (Omega-3 Fatty Acids for Prevention of Post-Operative Atrial Fibrillation), fixed in 10% buffered formalin, and embedded in paraffin for histology. We assessed general tissue morphology, cardiomyocyte diameters, myocytolysis (perinuclear myofibril loss), accumulation of perinuclear glycogen, interstitial fibrosis, and myocardial gap junction distribution. We also assayed NT-proBNP (N-terminal pro-B-type natriuretic peptide), hs-cTnT, CRP (C-reactive protein), and circulating oxidative stress biomarkers (F2-isoprostanes, F3-isoprostanes, isofurans) in plasma collected before, during, and 48 hours after surgery. POAF was defined as occurrence of postcardiac surgery atrial fibrillation or flutter of at least 30 seconds duration confirmed by rhythm strip or 12-lead ECG. The follow-up period for all arrhythmias was from surgery until hospital discharge or postoperative day 10.

RESULTS

Thirty-five percent of patients experienced POAF. Compared with the non-POAF group, they were slightly older and more likely to have chronic obstructive pulmonary disease or heart failure. They also had a higher European System for Cardiac Operative Risk Evaluation and more often underwent valve surgery. No differences in left atrial size were observed between patients with POAF and patients without POAF. The extent of atrial interstitial fibrosis, cardiomyocyte myocytolysis, cardiomyocyte diameter, glycogen score or Cx43 distribution at the time of surgery was not significantly associated with incidence of POAF. None of these histopathologic abnormalities were correlated with levels of NT-proBNP, hs-cTnT, CRP, or oxidative stress biomarkers.

CONCLUSIONS

In sinus rhythm patients undergoing cardiac surgery, histopathologic changes in the right atrial appendage do not predict POAF. They also do not correlate with biomarkers of cardiac function, inflammation, and oxidative stress. Graphic Abstract: A graphic abstract is available for this article.

Postoperative Atrial Fibrillation Following Cardiac Surgery: From Pathogenesis to Potential Therapies

Postoperative atrial fibrillation (POAF) is a major complication after cardiac surgery which can lead to high rates of morbidity and mortality, an enhanced length of hospital stay, and an increased cost of care. POAF is postulated to be a multifactorial phenomenon; however, some major pathogeneses have been proposed, including inflammatory pathways, oxidative stress, and autonomic dysfunction. Genetic studies also showed that inflammatory pathways, beta-1 adrenoreceptor variants, G protein-coupled receptor kinase 5 gene variants, and non-coding single-nucleotide polymorphisms in the 4q25 chromosomal locus are involved in this phenomenon. Moreover, several predisposing factors lead to the development of POAF, consisting of pre-, intra-, and postoperative contributors. The main predisposing factors comprise age, prior history of major cardiovascular risk factors, and ischemia-reperfusion injury during surgery. The management of POAF is based on the usual therapies used for non-surgical AF, including medications for either rate control or rhythm control in hemodynamically unstable patients. The perioperative administration of β-blockers and some antiarrhythmic agents has been recommended in major international guidelines. In addition, upstream therapies consisting of colchicine, magnesium, statins, and antioxidants have attenuated the incidence of POAF; however, some uncomfortable side effects developed in large randomized trials. The use of anticoagulation has also resulted in less mortality in patients with POAF at higher risk of thromboembolic events. Despite these recommendations, the actual regimen for the prevention of POAF remains controversial. In this review, we highlight the pathogenesis, predisposing factors, and potential therapeutic options for the management of patients at risk for or with POAF following cardiac surgery.

Incidence, Management, Prevention and Outcome of Post-Operative Atrial Fibrillation in Thoracic Surgical Oncology

Atrial fibrillation (AF) is a common supraventricular arrhythmia, a recognized risk factor for ischemic stroke, as a potential driver for heart failure (HF). Cancer patients have an increased risk for AF, even not including any cancer-specific treatment, as surgery or chemotherapy. The mechanism is multifactorial, with inflammation and changes in autonomic tone as critical actors. Commonly, AF is a recurrent complication of the post-operative period in cancer surgery (especially thoracic). Recent papers confirmed a significant incidence of post-operative (non-cardiac surgery) AF (PAF), partially mitigated by the use of prophylactic (rate o rhythm control) treatments. A relevant difference, in terms of mean hospitalization time, emerges between patients developing PAF and those who do not, while long term impact remains a matter of debate, due to several potential confounding factors. Besides clinical predictors, structural (i.e., echocardiographic) and bio-humoral findings may help in risk prediction tasks. In this respect, pre-operative natriuretic peptides (NPs) concentrations are nowadays recognized as significant independent predictors of perioperative cardiovascular complications (including PAF), while elevated post-operative levels may further enhance risk stratification. The aim of the present paper is to trace the state of the art in terms of incidence, management, prevention, and outcome of PAF in the field of thoracic surgical oncology.

Fibrosis independent atrial fibrillation in older patients is driven by substrate leukocyte infiltration: diagnostic and prognostic implications to patients undergoing cardiac surgery

Background

The objectives of the study were to characterize and quantify cellular inflammation and structural remodeling of human atria and correlate findings with molecular markers of inflammation and patient surrogate outcome.

Methods

Voluntary participants undergoing heart surgery were enrolled in the study and blood samples were collected prior to surgery, and right atrium samples were harvested intraoperatively. Blood samples were analyzed by flow cytometry and complete blood counts. Atrial samples were divided for fixed fibrosis analysis, homogenized for cytokine analysis and digested for single cell suspension flow cytometry.

Results

A total of 18 patients were enrolled and samples assessed. Isolated cells from the atria revealed a CD45+ population of ~ 20%, confirming a large number of leukocytes. Further characterization revealed this population as 57% lymphocytes and 26% monocyte/macrophages (MoΦ), with the majority of the latter cells being classical (CD14++/CD16−). Interstitial fibrosis was present in 87% of samples and correlated significantly with patient age. Older patients (> 65) had significantly more atrial fibrosis and cellular inflammation. AFib patients had no distinguishing feature of atrial fibrosis and had significantly greater CD45+ MoΦ, increased expression of MMP9 and presented with a significant correlation in length of stay to CCL-2/MCP-1 and NLR (neutrophil-to-lymphocyte ratio).

Conclusion

Atrial fibrosis is correlated with age and not determinate to AFib. However, severity of atrial leukocyte infiltration and markers of matrix degradation are determinant to AFib. This also correlated with CCL2 (or MCP-1) and NLR-indicative of marked inflammation. These data show the potential importance of diagnostic and prognostic assessments that could inform clinical decision making in regard to the intensity of AFib patient management.

Iron overload and arrhythmias: Influence of confounding factors

Arrhythmias as a cardiac complication of iron overload (IO) have been well described for decades in the clinical literature. They are assumed to be directly associated with the myocardial accumulation of iron. However, the influence of heart failure and elevated oxidative stress, which are major arrhythmogenic confounding factors associated with IO on arrhythmias, has not been critically reviewed in the published literature. A comprehensive narrative review of published articles in PubMed was conducted to address the influence of confounding factors of IO on arrhythmias. The previous data may have been largely confounded by the other cardiac complications of IO, particularly heart failure. The previous studies on IO-related arrhythmias lack proper age-gender-matched control subjects and/or comparison groups with properly controlled confounding factors to assess accurately their etiology and clinical significance. Given the above considerations, further mechanistic investigations to clarify the etiology and clinical relevance of IO-induced arrhythmias are needed. In addition, investigations to develop arrhythmia management strategy specific to IO, are warranted.

Urinary Biomarkers of Oxidative Stress in Atrial Fibrillation

There is increasing evidence from molecular studies to support the role of inflammation and increased oxidative stress that produce structural and electrical atrial remodeling to produce Atrial Fbrillation (AF). Oxidative damage to cardiomyocytes yields chemical substances that are secreted in urine. These substances can serve as biomarkers that can be measured, potentially allowing clinicians to quantify oxidative damage to the heart.

Oxidative Stress and Neonatal Respiratory Extracorporeal Membrane Oxygenation

Oxidative stress is a frequent condition in critically ill patients, especially if exposed to extracorporeal circulation, and it is associated with worse outcomes and increased mortality. The inflammation triggered by the contact of blood with a non-endogenous surface, the use of high volumes of packed red blood cells and platelets transfusion, the risk of hyperoxia and the impairment of antioxidation systems contribute to the increase of reactive oxygen species and the imbalance of the redox system. This is responsible for the increased production of superoxide anion, hydrogen peroxide, hydroxyl radicals, and peroxynitrite resulting in increased lipid peroxidation, protein oxidation, and DNA damage. The understanding of the pathophysiologic mechanisms leading to redox imbalance would pave the way for the future development of preventive approaches. This review provides an overview of the clinical impact of the oxidative stress during neonatal extracorporeal support and concludes with a brief perspective on the current antioxidant strategies, with the aim to focus on the potential oxidative stress-mediated cell damage that has been implicated in both short and long-term outcomes.

Arrhythmogenic Substrates for Atrial Fibrillation in Obesity

Global obesity rates have nearly tripled since 1975. This obesity rate increase is mirrored by increases in atrial fibrillation (AF) that now impacts nearly 10% of Americans over the age of 65. Numerous epidemiologic studies have linked incidence of AF and obesity and other obesity-related diseases, including hypertension and diabetes. Due to the wealth of epidemiologic data linking AF with obesity-related disease, mechanisms of AF pathogenesis in the context of obesity are an area of ongoing investigation. However, progress has been somewhat slowed by the complex phenotype of obesity; separating the effects of obesity from those of related sequelae is problematic. While the initiation of pathogenic pathways leading to AF varies with disease (including increased glycosylation in diabetes, increased renin angiotensin aldosterone system activation in hypertension, atrial ischemia in coronary artery disease, and sleep apnea) the pathogenesis of AF is united by shared mediators of altered conduction in the atria. We suggest focusing on these downstream mediators of AF in obesity is likely to yield more broadly applicable data. In the context of obesity, AF is driven by the interrelated processes of inflammation, atrial remodeling, and oxidative stress. Obesity is characterized by a constant low-grade inflammation that leads to increased expression of pro-inflammatory cytokines. These cytokines contribute to changes in cardiomyocyte excitability. Atrial structural remodeling, including fibrosis, enlargement, and fatty infiltration is a prominent feature of AF and contributes to the altered conduction. Finally, obesity impacts oxidative stress. Within the cardiomyocyte, oxidative stress is increased through both increased production of reactive oxygen species and by downregulation of scavenging enzymes. This increased oxidative stress modulates of cardiomyocyte excitability, increasing susceptibility to AF. Although the initiating insults vary, inflammation, atrial remodeling, and oxidative stress are conserved mechanisms in the pathophysiology of AF in the obese patients. In this review, we highlight mechanisms that have been shown to be relevant in the pathogenesis of AF across obesity-related disease.

Oxidative stress and atrial fibrillation: an update

Atrial remodelling involves electrophysiological and structural abnormalities that promote the development and perpetuation of atrial fibrillation. Experimental and clinical data indicate that oxidative stress is implicated in the pathophysiology of atrial remodelling. The mechanistic links between atrial remodelling and oxidative stress are complex with several underlying diseases and conditions may affect these pathways. Therefore, the development of antioxidant interventions in this setting remains difficult. Besides classical antioxidant compounds, several agents with pleiotropic effects, including anti-inflammatory and antioxidant, have been tested in experimental and clinical settings with variable results. Strategies applying conventional antioxidants in specific situations such as postoperative atrial fibrillation show beneficial effects, especially the two-step regimen of antioxidants combination. Of note, there are limited data on the development of strategies that target specific sources of reactive oxygen species implicated in atrial remodelling. Lifestyle, diet, and risk factors modification is a complementary promising approach. This updated review provides a concise and critical overview of all available data regarding oxidative stress and its modulation in atrial fibrillation. Future directions on this exciting field are also discussed.

New-onset atrial fibrillation: an update

New-onset atrial fibrillation (NOAF) is the most common perioperative complication of heart surgery, typically occurring in the perioperative period. NOAF commonly occurs in patients who are elderly, or have left atrial enlargement, or left ventricular hypertrophy. Various factors have been identified as being involved in the development of NOAF, and numerous approaches have been proposed for its prevention and treatment. Risk factors include diabetes, obesity, and metabolic syndrome. For prevention of NOAF, β-blockers and amiodarone are particularly effective and are recommended by guidelines. NOAF can be treated by rhythm/rate control, and antithrombotic therapy. Treatment is required in patients with decreased cardiac function, a heart rate exceeding 130 beats/min, or persistent NOAF lasting for ≥ 48 h. It is anticipated that anticoagulant therapies, as well as hemodynamic management, will also play a major role in the management of NOAF. When using warfarin as an anticoagulant, its dose should be adjusted based on PT-INR. PT-INR should be controlled between 2.0 and 3.0 in patients aged < 70 years and between 1.6 and 2.6 in those aged ≥ 70 years. Rate control combined with antithrombotic therapies for NOAF is expected to contribute to further advances in treatment and improvement of survival.

Lipid peroxidation in cardiac surgery: towards consensus on biomonitoring, diagnostic tools and therapeutic implementation

This review focuses on oxidative stress and more specifically lipid peroxidation in cardiac surgery, one of the fundamental theories of perioperative complications. We present the molecular pathways leading to lipid peroxidation and integrate analytical methods that allow detection of lipid peroxidation markers in the fluid phase with those focusing on volatile compounds in exhaled breath. In order to explore the accumulated data in the literature, we present a systematic review of quantitative analysis of malondialdehyde, a widely used lipid peroxidation product at various stages of cardiac surgery. This exploration reveals major limitations of existing studies in terms of variability of reported values and significant gaps due to discrete and variable sampling times during surgery. We also appraise methodologies that allow real-time and continuous monitoring of oxidative stress. Complimentary techniques highlight that beyond the widely acclaimed contribution of the cardiopulmonary bypass technology and myocardial reperfusion injury, the use of diathermy contributes significantly to intraoperative lipid peroxidation. We conclude that there is an urgent need to implement the theory of oxidative stress towards a paradigm change in the clinical practice. Firstly, we need to acquire definite and irrefutable information on the link between lipid peroxidation and post-operative complications by building international consensus on best analytical approaches towards generating qualitatively and quantitatively comparable datasets in coordinated multicentre studies. Secondly, we should move away from routine low-risk surgeries towards higher risk interventions where there is major unmet clinical need for improving patient journey and outcomes. There is also need for consensus on best therapeutic interventions which could be tested in convincing large scale clinical trials. As future directions, we propose combination of fluid phase platforms and 'metabography', an extended form of capnography-including real-time analysis of lipid peroxidation and volatile footprints of metabolism-for better patient phenotyping prior to and during high risk surgery towards molecular prediction, stratification and monitoring of the patient's journey.

Plasma Catecholamine Levels on the Morning of Surgery Predict Post-Operative Atrial Fibrillation

OBJECTIVES

This study sought to determine whether plasma catecholamines and monoamine oxidase-B (MOA-B) are associated with post-operative atrial fibrillation (POAF) in patients undergoing elective cardiac surgery.

BACKGROUND

Although intra- and post-operative adrenergic tone has been demonstrated to be an causative factor for POAF, the role and association of pre-operative plasma catecholamines remains unclear.

METHODS

Prior to administration of anesthesia on the morning of surgery, blood samples were obtained from 324 patients undergoing nonemergent coronary artery bypass graft and/or aortic valve surgery with cardiopulmonary bypass at East Carolina Heart Institute. The concentrations of norepinephrine (NE), dopamine (DA), epinephrine (EPI), and enzyme MAO-B were assessed in platelet-rich plasma. A log-binomial regression model was used to determine the association between quartiles of these variables and POAF.

RESULTS

Levels of NE (p = 0.0006) and EPI (p = 0.047) in the 4th quartile [Formula: see text] were positively associated with POAF, whereas DA (p = 0.0034) levels in the 4th quartile [Formula: see text] were inversely associated with POAF. Adjusting for age, heart failure (HF), and history of atrial fibrillation, the composite pre-operative (adrenergic) plasma marker [Formula: see text] was associated with a 4-fold increased occurrence of POAF (adjusted p = 0.0001). No association between plasma MAO-B and POAF was observed.

CONCLUSIONS

Our results suggest that pre-operative adrenergic tone is an important factor underlying POAF. This information provides evidence that assessment of plasma catecholamines may be a low-cost method that is easy to implement for predicting which patients are likely to develop POAF. More investigation in a multicentric setting is needed to validate our results.

Metabolomic Profiling in Relation to New-Onset Atrial Fibrillation (from the Framingham Heart Study)

Previous studies have shown several metabolic biomarkers to be associated with prevalent and incident atrial fibrillation (AF), but the results have not been replicated. We investigated metabolite profiles of 2,458 European ancestry participants from the Framingham Heart Study without AF at the index examination and followed them for 10 years for new-onset AF. Amino acids, organic acids, lipids, and other plasma metabolites were profiled by liquid chromatography-tandem mass spectrometry using fasting plasma samples. We conducted Cox proportional hazard analyses for association between metabolites and new-onset AF. We performed hypothesis-generating analysis to identify novel metabolites and hypothesis-testing analysis to confirm the previously reported associations between metabolites and AF. Mean age was 55.1 ± 9.9 years, and 53% were women. Incident AF developed in 156 participants (6.3%) in 10 years of follow-up. A total of 217 metabolites were examined, consisting of 54 positively charged metabolites, 59 negatively charged metabolites, and 104 lipids. None of the 217 metabolites met our a priori specified Bonferroni corrected level of significance in the multivariate analyses. We were unable to replicate previous results demonstrating associations between metabolites that we had measured and AF. In conclusion, in our metabolomics approach, none of the metabolites we tested were significantly associated with the risk of future AF.

Assessment of Isoprostanes in Human Plasma: Technical Considerations and the Use of Mass Spectrometry

Oxygenated lipid mediators released from non-enzymatic peroxidation of polyunsaturated fatty acids (PUFA) are known to have functional roles in humans. Notably, among these lipid mediators, isoprostanes molecules are robust biomarkers of oxidative stress but those from n-3 PUFA are also bioactive molecules. In order to identify and assess the isoprostanes, the use of mass spectrometry (MS) for analysis is preferable and has been used for over two decades. Gas chromatography (GC) is commonly coupled to the MS to separate the derivatized isoprostanes of interest in biological samples. In order to increase the accuracy of the analytical performance, GC-MS/MS was also applied. Lately, MS or MS/MS has been coupled with high-performance liquid chromatography to assess multiple isoprostane molecules in a single biological sample without derivatization process. However, there are limitations for the use of LC-MS/MS in the measurement of plasma isoprostanes, which will be discussed in this review.

The novelty of phytofurans, isofurans, dihomo-isofurans and neurofurans: Discovery, synthesis and potential application

Polyunsaturated fatty acids (PUFA) are oxidized in vivo under oxidative stress through free radical pathway and release cyclic oxygenated metabolites, which are commonly classified as isoprostanes and isofurans. The discovery of isoprostanes goes back twenty-five years compared to fifteen years for isofurans, and great many are discovered. The biosynthesis, the nomenclature, the chemical synthesis of furanoids from α-linolenic acid (ALA, C18:3 n-3), arachidonic acid (AA, C20:4 n-6), adrenic acid (AdA, 22:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) as well as their identification and implication in biological systems are highlighted in this review.

Low preoperative selenium is associated with post-operative atrial fibrillation in patients having intermediate-risk coronary artery surgery

BACKGROUND/OBJECTIVES

Post-operative atrial fibrillation (POAF) is a frequent complication of cardiac surgery. Oxidative stress and reduced antioxidant function have major roles in its development. Selenium is a key to normal antioxidant function, and levels are often low before cardiac surgery. This study investigated whether low preoperative selenium levels were associated with POAF in cardiac surgical patients.

SUBJECTS/METHODS

Using the Society of Thoracic Surgeons (STS) Mortality risk score, 50 patients having primary coronary artery bypass grafts (CABG) surgery were divided into two groups: (i) low-risk group (STS ⩽0.5%; n=26) and (ii) intermediate-risk group (STS ⩾2.0%; n=24). Plasma levels of selenium, glutathione peroxidase (GPx) and malondialdehyde (MDA) were measured in all patients at anaesthetic induction, after aortic cross-clamp removal, 3 h post cardiopulmonary bypass and on post-operative days 1 and 5. Multiple logistic regression was used to assess whether selenium levels were associated with POAF development.

RESULTS

Seventeen patients developed POAF (14 patients in the intermediate-risk group and 3 patients in the low-risk group). Preoperative selenium was lower in patients who developed POAF compared with those with normal sinus rhythm (0.73±0.16 vs 0.89±0.13 μmol/l, P=0.005), and this was independently associated with POAF (PR 0.32; 95% confidence credible interval (95%cI) 0.06-0.85, P=0.016). Regardless of POAF, preoperative selenium was lower in the intermediate-risk patients than in the low-risk patients (0.77±0.15 vs 0.89±0.14 μmol/l; P=0.004).

CONCLUSIONS

Intermediate-risk patients with low preoperative selenium levels may be at a greater risk of developing POAF following CABG. This raises the question of whether selenium supplementation in select cardiac surgical patients may reduce their POAF risk.

Pathophysiology of cancer therapy-provoked atrial fibrillation

Atrial fibrillation (AF) occurs with increased frequency in cancer patients, especially in patients who undergo surgery or chemotherapy. AF disturbs the prognosis of cancer patients and challenges therapeutic outcomes of cancer treatment. Elucidating the mechanisms of cancer-induced AF would help identify specific strategies for preventing AF occurrence. In addition to concurrent risk factors of cancer and AF, cancer surgery, side effects of anticancer agents, and cancer-associated immune responses play critical roles in the genesis of AF. In this review, we provide succinct potential mechanisms of AF genesis in cancer patients.

Upstream Treatment of Atrial Fibrillation with n-3 Polyunsaturated Fatty Acids: Myth or Reality?

Atrial fibrillation (AF) is the most common sustained arrhythmia in adults and is associated with an increased risk of fatal and non-fatal events. Antiarrhythmic drugs provide limited protection against AF recurrence and have a poor safety profile. Several mechanisms have been proven to be involved in AF, e.g. inflammation, oxidative stress, fibrosis and ischaemia. Prevention of AF with interventions that target these mechanisms has emerged as a result of experimental studies suggesting the use of upstream therapies. Long chain n-3 polyunsaturated fatty acids (n-3 PUFA) have multiple effects on cardiac electrophysiology, and epidemiological studies on fish oil suggest a possible use of n-3 PUFA in AF prevention. Several randomised clinical trials have been designed to evaluate the efficacy of n-3 PUFA in preventing AF. In this review, we report the conflicting results of these trials in two different clinical settings: recurrence in patients with history of AF and development of post-operative AF in patient undergoing cardiac surgery.