Atrial Fibrillation After Cardiac Surgery/Cardiopulmonary Bypass Is Associated with Monocyte Activation

Leukocyte filtration and leukocyte modulation therapy during extracorporeal cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest

Extracorporeal cardiopulmonary resuscitation (ECPR) is emerging as a feasible and effective rescue strategy for prolonged cardiac arrest (CA). However, prolonged total body ischemia and reperfusion can cause microvascular occlusion that prevents organ reperfusion and recovery of function. One hypothesized mechanism of microvascular "no-reflow" is leukocyte adhesion and formation of neutrophil extracellular traps. In this study we tested the hypothesis that a leukocyte filter (LF) or leukocyte modulation device (L-MOD) could reduce NETosis and improve recovery of heart and brain function in a swine model of prolonged cardiac arrest treated with ECPR. Thirty-six swine (45.5 ± 2.5 kg, evenly distributed sex) underwent 8 min of untreated ventricular fibrillation CA followed by 30 min of mechanical CPR with subsequent 8 h of ECPR. Two females were later excluded from analysis due to CPR complications. Swine were randomized to standard care (Control group), LF, or L-MOD at the onset of CPR. NET formation was quantified by serum dsDNA and citrullinated histone as well as immunofluorescence staining of the heart and brain for citrullinated histone in the microvasculature. Primary outcomes included recovery of cardiac function based on cardiac resuscitability score (CRS) and recovery of neurologic function based on the somatosensory evoked potential (SSEP) N20 cortical response. In this model of prolonged CA treated with ECPR we observed significant increases in serum biomarkers of NETosis and immunohistochemical evidence of microvascular NET formation in the heart and brain that were not reduced by LF or L-MOD therapy. Correspondingly, there were no significant differences in CRS and SSEP recovery between Control, LF, and L-MOD groups 8 h after ECPR onset (CRS = 3.1 ± 2.7, 3.7 ± 2.6, and 2.6 ± 2.6 respectively; p = 0.606; and SSEP = 27.9 ± 13.0%, 36.7 ± 10.5%, and 31.2 ± 9.8% respectively, p = 0.194). In this model of prolonged CA treated with ECPR, the use of LF or L-MOD therapy during ECPR did not reduce microvascular NETosis or improve recovery of myocardial or brain function. The causal relationship between microvascular NETosis, no-reflow, and recovery of organ function after prolonged cardiac arrest treated with ECPR requires further investigation.

New-Onset Sleep Disorders before Cardiac Surgery May Indicate an Increased Risk of Postoperative Atrial Fibrillation

PURPOSE

We aimed to determine if sleep disorders before cardiac surgery indicate an increased risk of postoperative atrial fibrillation (POAF).

METHODS

In this study, 238 patients undergoing coronary artery bypass grafting in our center were included. Patients were separated into the preoperative sleep disorder group and the control group. The primary endpoint was the incidence of POAF, and the secondary endpoints were the incidence of postoperative stroke, duration of invasive ventilation, length of intensive care unit, and hospitalization stay. Propensity score matching and multivariable logistic regression were used for adjusting potential confounders.

RESULTS

A total of 165 (69.3%) patients had sleep disorders before surgery, and 73 well-matched pairs were generated. A higher incidence of POAF was found in the preoperative sleep disorder group (16.4% versus 5.5%, p = 0.034). In multivariable logistic regression, preoperative sleep disorders were correlated to a higher risk of POAF (odds ratio = 4.627, 95% confidence interval: 1.181-18.123, p = 0.028). In the subgroup of patients without long-term sleep disorders, those who experienced preoperative sleep disorders had a higher incidence of POAF (16.1% versus 4.3%, p = 0.024), meanwhile, no difference was found in the subgroup of long-term sleep disorders.

CONCLUSION

New-onset sleep disorders before cardiac surgery may indicate a higher incidence of POAF.

Monocyte to high-density lipoprotein ratio predicts clinical outcomes after acute ischemic stroke or transient ischemic attack

AIMS

The monocyte to high-density lipoprotein cholesterol ratio (MHR) has emerged as a novel inflammatory biomarker of atherosclerotic cardiovascular disease. However, it has not yet been identified whether MHR can predict the long-term prognosis of ischemic stroke. We aimed to investigate the associations of MHR levels with clinical outcomes in patients with ischemic stroke or transient ischemic attack (TIA) at 3 months and 1 year.

METHODS

We derived data from the Third China National Stroke Registry (CNSR-III). Enrolled patients were divided into four groups by quartiles of MHR. Multivariable Cox regression for all-cause death and stroke recurrence and logistic regression for the poor functional outcome (modified Rankin Scale score 3-6) were used.

RESULTS

Among 13,865 enrolled patients, the median MHR was 0.39 (interquartile range, 0.27-0.53). After adjustment for conventional confounding factors, the MHR level in quartile 4 was associated with an increased risk of all-cause death (hazard ratio [HR], 1.45; 95% confidence interval [CI], 1.10-1.90), and poor functional outcome (odd ratio [OR], 1.47; 95% CI, 1.22-1.76), but not with stroke recurrence (HR, 1.02; 95% CI, 0.85-1.21) at 1 year follow-up, compared with MHR level in quartile 1. Similar results were observed for outcomes at 3 months. The addition of MHR to a basic model including conventional factors improved predictive ability for all-cause death and poor functional outcome validated by the C-statistic and net reclassification index (all p < 0.05).

CONCLUSIONS

Elevated MHR can independently predict all-cause death and poor functional outcome in patients with ischemic stroke or TIA.

The monocyte-to-high-density lipoprotein ratio is associated with the occurrence of atrial fibrillation among NAFLD patients: A propensity-matched analysis

BACKGROUND

Accumulating evidence suggests that patients with nonalcoholic fatty liver disease (NAFLD) have a significantly high risk of incident atrial fibrillation (AF). Systemic inflammation, metabolic disorders and oxidative stress could be the potential mechanisms by which NAFLD drives AF. Monocyte-to- high-density lipoprotein ratio (MHR) has emerged as a novel biomarker of inflammation and oxidative stress that has not been studied in AF with NAFLD patients. We aimed to investigate the relationship between MHR and the risk of AF among NAFLD patients.

METHODS

A retrospective analysis was performed for the clinical data of the patients with NAFLD in the Second Hospital of Shanxi Medical University from January 2019 to October 2022, among whom 204 patients with AF were enrolled as NAFLD+AF group and 613 patients without AF were enrolled as NAFLD control, and 152 patients were selected from each group based on propensity score matching (PSM) at a ratio of 1:1 to balance the covariates between groups. The t-test or the Mann-Whitney U test was used for comparison of continuous data between two groups; the chi-square test or the Fisher's exact test was used for comparison of categorical data between two groups. Logistic regression analysis was performed to identify the independent predictor for occurrence of AF among NAFLD patients. Trend chi-square test to analyze the prevalence of AF among MHR tertiles, and then the correlation between MHR and the risk of AF confirmed by restricted cubic splines (RCS). The receiver operating characteristic (ROC) curve analysis was used to determine the optimum MHR cutoff value to predict AF.

RESULTS

Univariate analysis showed that AF patients had higher MHR than non-AF patients (P < 0.001). Meanwhile, compared with pure NAFLD patients, multivariate logistic regression analysis showed that MHR remained to be an independent risk factor for AF after adjusting for confounding risk factors (OR = 10.67, 95% CI 2.17-52.37, P = 0.004). TC、HDL-C were also independent risk factors for AF. Among them, TC and HDL-C are protective factors for AF. The trend chi-square test showed that the risk of AF increased with an increase in MHR (P < 0.05). However, the RCS showed a nonlinear and J-shaped relationship between MHR and the risk of AF (P for non-linearity = 0.023). The occurrence of AF increased with increasing MHR only when MHR > 0.44. The ROC curve showed that MHR combined with traditional risk factors can improve the ability to predict AF.

CONCLUSION

MHR is an independently associated with incident AF in patients with NAFLD and show a certain predictive value.

The Role of Major Inflammatory Biomarkers in the Pathogenesis of Atrial Fibrillation

Many studies have reported a relationship between inflammation and atrial fibrillation (AF). According to the literature, inflammation is the key component in pathophysiological processes during the development of AF; the amplification of inflammatory pathways triggers AF, and, at the same time, AF increases the inflammatory state. The plasma levels of several inflammatory biomarkers are elevated in patients with AF; therefore, inflammation might contribute to both the maintenance and occurrence of AF and its thromboembolic complications. Numerous inflammatory markers have been linked to AF, including CD40 ligand, fibrinogen, matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein-1, myeloperoxidase, plasminogen activator inhibitor-1, and serum amyloid A. There are many pathophysiological aspects of AF that are linked to these inflammatory biomarkers, including atrial structural remodeling and atrial dilatation, increased atrial myocyte expression, fluctuations in calcium cycling, cardiac remodeling promotion, increased cardiac myocyte proliferation and terminal differentiation, production of several MMPs, the pathogenesis of atherosclerosis and cardiomyocyte apoptosis, an increased degree of fibrosis in atrial myocardium, and the progression and development of atherogenesis and atherothrombosis. The present review article aims to provide an updated overview and focus on the basic role of different biomarkers of inflammation in the pathophysiological aspects of the pathogenesis of AF.

Myeloperoxidase Levels in Pericardial Fluid Is Independently Associated with Postoperative Atrial Fibrillation after Isolated Coronary Artery Bypass Surgery

BACKGROUND

Postoperative atrial fibrillation (POAF) is the most common complication after surgery for atherosclerotic cardiovascular disease (ASCVD) and leads to extended hospital stays and increased mortality. Myeloperoxidase (MPO) in postoperative pericardial drainage fluid is associated with an increased risk of POAF; however, the correlations between MPO in intraoperative pericardial fluid and POAF remain largely unknown. The aim of the study was to evaluate whether MPO is associated with POAF.

METHODS

A total of 97 patients with no history of atrial arrhythmia who had undergone coronary artery bypass surgery (CABG) were identified. We prospectively measured the levels of MPO in intraoperative pericardial fluid and blood using the human magnetic Luminex assay. Then, the occurrence of atrial fibrillation was continuously observed by postoperative ECG and telemetry strips until discharge.

RESULTS

Our data showed that POAF occurred in 24 of 97 patients (24.74%). MPO levels in blood were higher in the POAF group than the SR group (p = 0.064). Patients with POAF had significantly higher intraoperative pericardial fluid MPO levels than patients who remained in SR (p = 0.021). There was no significant correlation between pericardial fluid MPO levels and blood MPO levels (r = -0.47, p = 0.770). In a multivariable logistic regression model, pericardial fluid MPO levels were significantly associated with a higher risk of POAF (odds ratio = 1.016, 95% confidence interval, 1.001-1.031; p = 0.031).

CONCLUSIONS

Higher intraoperative pericardial fluid MPO levels are linked with POAF in patients undergoing CABG. This finding provides insight into a possible mechanism of MPO in pericardial fluid increase susceptibility to developing POAF in patients undergoing CABG.

Exploring the causality between ankylosing spondylitis and atrial fibrillation: A two-sample Mendelian randomization study

Objective: To study whether ankylosing spondylitis (AS) has a causal effect on the risk of atrial fibrillation (AF) using two-sample Mendelian randomization (MR) analysis. Methods: Single nucleotide polymorphisms (SNPs) were selected as independent instrumental variables (IVs) from a GWAS study of AS. Summary data from a large-scale GWAS meta-analysis of AF was utilized as the outcome dataset. Inverse-variance weighted (IVW) model was used for the primary analysis. Multiple sensitivity and heterogeneity tests were conducted to confirm the robustness of the results. Results: In total, 18 SNPs were identified as IVs for MR analysis. Five MR methods consistently found that ankylosing spondylitis was not causally associated with atrial fibrillation (IVW: OR = 0.983 (0.894, 1.080), p = 0.718; MR-Egger: OR = 1.190 (0.973, 1.456), p = 0.109; Simple mode: OR = 0.888 (0.718, 1.098), p = 0.287; Weighted mode: OR = 0.989 (0.854, 1.147), p = 0.890; Weight median: OR = 0.963 (0.852, 1.088), p = 0.545). Leave-one-out analysis supported the stability of MR results. Both the MR-Egger intercept and MR-PRESSO method revealed the absence of horizontal pleiotropy. Conclusion: The two-sample MR analysis did not support a causal relationship between AS and the risk of AF.

Immune-associated pivotal biomarkers identification and competing endogenous RNA network construction in post-operative atrial fibrillation by comprehensive bioinformatics and machine learning strategies

Background

Atrial fibrillation (AF) is the most common arrhythmia. Previous studies mainly focused on identifying potential diagnostic biomarkers and treatment strategies for AF, while few studies concentrated on post-operative AF (POAF), particularly using bioinformatics analysis and machine learning algorithms. Therefore, our study aimed to identify immune-associated genes and provide the competing endogenous RNA (ceRNA) network for POAF.

Methods

Three GSE datasets were downloaded from the GEO database, and we used a variety of bioinformatics strategies and machine learning algorithms to discover candidate hub genes. These techniques included identifying differentially expressed genes (DEGs) and circRNAs (DECs), building protein-protein interaction networks, selecting common genes, and filtering candidate hub genes via three machine learning algorithms. To assess the diagnostic value, we then created the nomogram and receiver operating curve (ROC). MiRNAs targeting DEGs and DECs were predicted using five tools and the competing endogenous RNA (ceRNA) network was built. Moreover, we performed the immune cell infiltration analysis to better elucidate the regulation of immune cells in POAF.

Results

We identified 234 DEGs (82 up-regulated and 152 down-regulated) of POAF via Limma, 75 node genes were visualized via PPI network, which were mainly enriched in immune regulation. 15 common genes were selected using three CytoHubba algorithms. Following machine learning selection, the nomogram was created based on the four candidate hub genes. The area under curve (AUC) of the nomogram and individual gene were all over 0.75, showing the ideal diagnostic value. The dysregulation of macrophages may be critical in POAF pathogenesis. A novel circ_0007738 was discovered in POAF and the ceRNA network was eventually built.

Conclusion

We identified four immune-associated candidate hub genes (C1QA, C1R, MET, and SDC4) for POAF diagnosis through the creation of a nomogram and evaluation of its diagnostic value. The modulation of macrophages and the ceRNA network may represent further therapy methods.

Bioinformatics Analysis of Competing Endogenous RNA Network and Immune Infiltration in Atrial Fibrillation

Background

There is still no clear understanding of the pathogenesis of atrial fibrillation (AF). For this purpose, we used integrated analysis to uncover immune infiltration characteristics and investigated their relationship with competing endogenous RNA (ceRNA) network in AF.

Methods

Three AF mRNA data sets (GSE14975, GSE79768, and GSE41177) were integrated using the SVA method from Gene Expression Omnibus (GEO). Together with AF circRNA data set (GSE129409) and miRNA data set (GSE70887) from GEO database, we built a ceRNA network. Then hub genes were screened by the Cytoscape plug-in cytoHubba from a protein-protein interaction (PPI) network. As well, CIBERSORT was employed to investigate immune infiltration, followed by Pearson correlation coefficients to unravel the correlation between AF-related infiltrating immune cells and hub genes. Ulteriorly, circRNA-miRNA-mRNA regulatory axises that could be immunologically related to AF were obtained.

Results

Ten hub genes were identified from the constructing PPI network. The immune infiltration analysis revealed that the number of monocytes and neutrophils was higher, as well as the number of dendritic cells activated and T cells regulatory (Tregs) was lower in AF. Seven hub genes (C5AR1, CXCR4, HCK, LAPTM5, MPEG1, TLR8, and TNFSF13B) were associated with those 4 immune cells (P < 0.05). We found that the circ_0005299–miR-1246–C5AR1 and circRNA_0079284-miR-623-HCK/CXCR4 regulatory axises may be associated with the immune mechanism of AF.

Conclusion

The findings of our study provide insights into immuno-related ceRNA networks as potential molecular regulators of AF progression.

Short acting intravenous beta-blocker as a first line of treatment for atrial fibrillation after cardiac surgery: a prospective observational study

Post-operative atrial fibrillation (POAF) defined as a new-onset of atrial fibrillation (AF) following surgery occurs frequently after cardiac surgery. For non-symptomatic patients, rate control strategy seems to be as effective as rhythm control one in surgical patients. Landiolol is a new highly cardio-selective beta-blocker agent with interesting pharmacological properties that may have some interest in this clinical situation. This is a prospective, monocentric, observational study. All consecutive adult patients (age >18 years old) admitted in the intensive care unit following cardiac surgery with a diagnosed episode of AF were eligible. Success of landiolol administration was defined by a definitive rate control from the beginning of infusion to the 72th h. We also evaluated rhythm control following landiolol infusion. Safety analysis was focused on haemodynamic, renal and respiratory side effects. From 1 January 2020 to 30 June 2021, we included 54 consecutive patients. A sustainable rate control was obtained for 49 patients (90.7%). Median time until a sustainable rate control was 4 h (1, 22). Median infusion rate of landiolol needed for a sustainable rate control was 10 µg/kg/min (6, 19). Following landiolol infusion, median time until pharmacological cardioversion was 24 h. During landiolol infusion, maintenance of mean arterial pressure target requires a concomitant very low dose of norepinephrine. We did not find any other side effects. Low dose of landiolol used for POAF treatment was effective and safe for a rapid and sustainable rate and rhythm control after cardiac surgery.

The Construction and Comprehensive Analysis of a ceRNA Immunoregulatory Network and Tissue-Infiltrating Immune Cells in Atrial Fibrillation

Background

At present, the mechanisms behind atrial fibrillation (AF) pathogenesis are still unclear. We construct a ceRNA immunoregulatory network to further understand the mechanism of AF.

Methods

Four AF mRNA datasets from the Gene Expression Omnibus (GEO) database were integrated by SVA method. AF-related immune genes (AF-IRGs) were selected via combining ImmPort database with the genes in the module most associated with AF obtained by a weighted gene coexpression network analysis (WGCNA). Then, circRNA and miRNA expressions from the GEO database were extracted and mapped with related databases. Next, an immune-related circRNA-miRNA-mRNA ceRNA network was constructed and hub genes were filtered from a protein–protein interaction (PPI) network, and the differentially expressed (DE) hub genes in AF were further screened. Additionally, immune infiltration was investigated in AF by using CIBERSORT. Subsequently, the relationships between DE hub genes and AF-related infiltrating immune cells were performed by using Pearson correlation coefficients. Ulteriorly, the immune-cells-related ceRNA subnetwork in AF was built.

Results

A total of 95 AF-IRGs were detected, and an immune-related ceRNA network in AF was constructed with 12 circRNAs, 7 miRNAs and 50 mRNAs. The immune infiltration analysis indicated that a higher level of neutrophils, as well as a lower level of T cells regulatory (Tregs) and NK cells activated in AF. Four DE hub genes (CXCL12, IL7R, TNFSF13B, CD8A) were associated with Tregs or NK cells activated immune cells (P < 0.05). Tregs or NK cells activated immune cells-related ceRNA subnetwork including 5 circRNAs (has_circ_0001190, has_circ_0006725, has_circ_0079284, has_circ_0005299, and has_circ_0002103), 4 miRNAs (has-miR-198, has-miR-623, has-miR-1246, and has-miR-339-3p) and 4 DE hub genes was eventually constructed in AF.

Conclusion

Our results provide new insights into the molecular mechanisms governing AF progression from the perspective of immune-related ceRNA network.

Multiomics Analysis of Genetics and Epigenetics Reveals Pathogenesis and Therapeutic Targets for Atrial Fibrillation

Objective

This study is aimed at understanding the molecular mechanisms and exploring potential therapeutic targets for atrial fibrillation (AF) by multiomics analysis.

Methods

Transcriptomics and methylation data of AF patients were retrieved from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) and differentially methylated sites between AF and normal samples were screened. Then, highly expressed and hypomethylated and lowly expressed and hypermethylated genes were identified for AF. Weighted gene coexpression network analysis (WGCNA) was presented to construct AF-related coexpression networks. 52 AF blood samples were used for whole exome sequence. The mutation was visualized by the maftools package in R. Key genes were validated in AF using independent datasets.

Results

DEGs were identified between AF and controls, which were enriched in neutrophil activation and regulation of actin cytoskeleton. RHOA, CCR2, CASP8, and SYNPO2L exhibited abnormal expression and methylation, which have been confirmed to be related to AF. PCDHA family genes had high methylation and low expression in AF. We constructed two AF-related coexpression modules. Single-nucleotide polymorphism (SNP) was the most common mutation type in AF, especially T > C. MUC4 was the most frequent mutation gene, followed by PHLDA1, AHNAK2, and MAML3. There was no statistical difference in expression of AHNAK2 and MAML3, for AF. PHLDA1 and MUC4 were confirmed to be abnormally expressed in AF.

Conclusion

Our findings identified DEGs related to DNA methylation and mutation for AF, which may offer possible therapeutic targets and a new insight into the pathogenesis of AF from a multiomics perspective.

Association between atrial fibrillation and white blood cell count after the Great East Japan Earthquake: An observational study from the Fukushima Health Management Survey

We had earlier reported about the increase in the prevalence of atrial fibrillation (AF) among residents in the evacuation zone of Fukushima Prefecture after the Great East Japan Earthquake. In the present investigation, we explored the association between the prevalence of AF and white blood cell (WBC) count after the earthquake through an observational cross-sectional study.A total of 14,800 participants (6427 men and 8373 women) were included in the Fukushima Health Management Survey. For the present study, 12-lead electrocardiogram tracings and the WBC count and its subtypes were obtained and analyzed. The odds ratios (ORs) of AF after the earthquake and the 95% confidence intervals (CIs) for one standard deviation of differential WBC count were calculated after adjustments for age and other potential confounding factors using the logistic regression model.Our results revealed a prevalence of AF of 1.8% (269 participants) after the earthquake. Monocyte count and neutrophil/lymphocyte ratio exhibited a significant association with the prevalence of AF in the multivariable-adjusted model. The adjusted ORs of monocyte count and neutrophil/lymphocyte ratio for AF were 1.21 (95% CI, 1.05-1.40, P = .01) and 1.22 (95% CI, 1.01-1.44, P < .05), respectively.The prevalence of AF was associated with increased monocyte count and neutrophil/lymphocyte ratio among residents in the evacuation zone in Fukushima Prefecture, suggesting that inflammation and psychological stress could be important factors mediating the development of AF after the earthquake.

Circulating intermediate monocytes and atrial structural remodeling associated with atrial fibrillation recurrence after catheter ablation

BACKGROUND

Inflammation, such as that associated with intermediate CD14⁺⁺ CD16⁺ monocytes and atrial structural remodeling (SRM), may be important in the recurrence of atrial fibrillation (AF) after catheter ablation. However, the relationship between the intermediate CD14⁺⁺ CD16⁺ monocytes, SRM, and AF recurrence is unclear.

METHODS

Twenty-four patients with AF were enrolled. The proportion of intermediate monocytes (PIM) was assessed before ablation by flow cytometry. As a surrogate marker of SRM, the volume ratio (VR) of signal intensity greater than 1 standard deviation on late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) was calculated. We investigated whether PIM correlated with SRM on LGE-MRI and determined the optimal cutoff value for predicting AF recurrence.

RESULTS

Univariate analysis revealed positive correlations between PIM and BNP with SRM (PIM: r = .593, p = .002; BNP: r = .567, p = .004). Multivariable analysis revealed that PIM was independently associated with VR on LGE-MRI (β = .522; p = .033). The finding of an area under the receiver operating characteristic curve of 0.750 revealed that a VR ≥ 13.3% on LGE-MRI as the optimal cutoff value to predict AF recurrence with 80% sensitivity and 71% specificity, which was associated with PIM ≥ 10.0%.

CONCLUSION

Intermediate monocytes were significantly positively correlated with SRM. PIM ≥ 10% was associated with a VR ≥ 13.3% on LGE-MRI, which predicted AF recurrence after catheter ablation.

Impact of Denervation by Heart Transplantation on Post-operative Atrial Fibrillation Susceptibility

Atrial fibrillation is common following cardiac and non-cardiac thoracic surgery and is associated with poorer outcomes, including: increased risk of stroke, hemodynamic instability, prolonged hospital stay, and increased mortality. Current understanding suggests that post-op atrial fibrillation results from the interplay of local and systemic operative inflammation, increased sympathetic activity, perhaps the release of free radical species in the perioperative period, and the patient's underlying cardiac substrate. Cardiac denervation following orthotopic heart transplant (OHT) using modern bicaval techniques presents a unique opportunity to study the relative contribution of the autonomic nervous system to post-op atrial fibrillation susceptibility. Observational studies show a reduced incidence of post-operative atrial fibrillation following orthotopic heart transplant compared to other cardiac and thoracic surgeries. Moreover, comparison of atrial fibrillation rates with double lung transplant recipients suggests that cardiac denervation has a contribution apart from surgical pulmonary vein isolation alone. This report reviews current concepts of the mechanisms of post-op atrial fibrillation with a focus on the role of the autonomic nervous system, the autonomic regulation of the native heart, and evidence regarding the impact of cardiac denervation following OHT.

Inflammasomes and Proteostasis Novel Molecular Mechanisms Associated With Atrial Fibrillation

Atrial fibrillation (AF), the most common progressive and age-related cardiac arrhythmia, affects millions of people worldwide. AF is associated with common risk factors, including hypertension, diabetes mellitus, and obesity, and serious complications such as stroke and heart failure. Notably, AF is progressive in nature, and because current treatment options are mainly symptomatic, they have only a moderate effect on prevention of arrhythmia progression. Hereto, there is an urgent unmet need to develop mechanistic treatments directed at root causes of AF. Recent research findings indicate a key role for inflammasomes and derailed proteostasis as root causes of AF. Here, we elaborate on the molecular mechanisms of these 2 emerging key pathways driving the pathogenesis of AF. First the role of NLRP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome on AF pathogenesis and cardiomyocyte remodeling is discussed. Then we highlight pathways of proteostasis derailment, including exhaustion of cardioprotective heat shock proteins, disruption of cytoskeletal proteins via histone deacetylases, and the recently discovered DNA damage-induced nicotinamide adenine dinucleotide⁺ depletion to underlie AF. Moreover, potential interactions between the inflammasomes and proteostasis pathways are discussed and possible therapeutic targets within these pathways indicated.

Evidence for Inflammation as a Driver of Atrial Fibrillation

Atrial fibrillation (AF) is one of the most common types of arrhythmias and increases cardiovascular morbidity and mortality. Current therapeutic approaches to AF that focus on rhythm control have high recurrence rates and no life prolongation value. While possible explanations include toxicity of current therapies, another likely explanation may be that current therapies do not address fundamental mechanisms of AF initiation and maintenance. Inflammation has been shown to affect signaling pathways that lead to the development of AF. This paper reviews the roles of inflammation in the occurrence, development, and mechanisms of AF and reviews the therapeutic implications of the correlation of inflammation and AF.

Evaluation of Inflammation Caused by Cardiopulmonary Bypass in a Small Animal Model

Extracorporeal circulation (ECC) methods are being increasingly used for mechanical support of respiratory and cardio-circulatory failure. Especially, cardiopulmonary bypass (CPB) during cardiovascular surgery, sustenance of the patient’s life by providing an appropriate blood flow and oxygen supply to principal organs. On the other hand, systemic inflammatory responses in patients undergoing cardiovascular surgery supported by CPB contribute significantly to CPB-associated mortality and morbidity. Our previous research showed that CPB causes a systemic inflammatory response and organ damage in a small animal CPB model. We have been studying the effects of hyperoxia and blood plasma substitute on CPB. In this review, we present a study focusing on the systemic inflammatory response during CPB, along with our findings.

Integrative analysis of transcriptome-wide association study data and mRNA expression profiles identified candidate genes and pathways associated with atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia characterized by extensive structural, contractile and electrophysiological remodeling. The genetic basis of AF remained elusive until now. Transcriptome-wide association study (TWAS) was conducted by FUSION tool using gene expression weights of 7 tissues combined with a large-scale genome-wide association study (GWAS) dataset of AF, totally involving 8180 AF cases and 28,612 controls. Significant genes identified by TWAS were then subjected to gene ontology (GO) and pathway enrichment analysis. The genome-wide mRNA gene expression profiling of AF was compared with the results of TWAS to detect common genes shared by TWAS and mRNA expression profiling of AF. TWAS detected a group of candidate genes with P_TWAS values < 0.05 across the seven tissues for AF, such as CMAH (P_TWAS = 3.15 × 10^-25 for whole blood), INCENP (P_TWAS = 1.77 × 10^-22 for artery aorta), CMAHP (P_TWAS = 4.57 × 10^-20 for artery aorta). Pathway enrichment analysis identified multiple candidate pathways, such as protein K48-linked ubiquitination (P value = 0.0124), positive regulation of leukocyte chemotaxis (P value = 0.0046) and fatty acid degradation (P value = 0.0295). Further comparing the GO results of TWAS and mRNA expression profiling, 2 common GO terms were identified, including actin binding (P_TWAS = 0.0446, P_mRNA = 7.00 × 10^-4) and extracellular matrix (P_TWAS = 0.0037, P_mRNA = 3.00 × 10^-6). We detected multiple novel candidate genes, GO terms and pathways for AF, providing novel clues for understanding the genetic mechanism of AF.

Reduction of atrial fibrillation burden by pulmonary vein isolation leads to a decrease of CD11b expression on inflammatory cells

Aims

It is hypothesized that inflammation could promote structural and electrical remodelling processes in atrial fibrillation (AF). Atrial infiltration of monocytes and granulocytes has been shown to be dependent on CD11b expression. The aim of this study was to investigate whether treatment of AF by pulmonary vein isolation (PVI) may lead to reduced inflammation, as indicated by a decrease of CD11b expression on monocytes and granulocytes.

Methods and results

Flow-cytometric quantification analysis and determination of systemic inflammatory markers of peripheral blood were performed in 75 patients undergoing PVI 1 day before and 6 months after PVI. The extent of activation of monocytes and granulocytes was measured by quantifying the cell adhesion molecule CD11b. The mean expression of CD11b on monocytes (20.9 ± 2.5 vs. 10.2 ± 1.4; P < 0.001) and granulocytes (13.9 ± 1.6 vs. 6.8 ± 0.5; P < 0.001), as well as the relative count of CD11b-positive monocytes (P < 0.05) and CD11b-positive granulocytes (P < 0.01) were significantly reduced when comparing the identical patients before and 6 months after PVI. Systemic inflammatory parameters showed only a declining tendency after 6 months. Patients with unsuccessful PVI and ongoing AF on the day of follow-up showed no decrease in CD11b expression.

Conclusions

A significant reduction of CD11b expression on monocytes and granulocytes, as a sign of reduced cellular inflammation, was achieved by treatment of AF using PVI. These data strongly support that AF is not only a consequence of but also a cause for inflammatory processes, which, in turn, may contribute to atrial remodelling.

Role of inflammatory signaling in atrial fibrillation

Atrial fibrillation (AF), the most prevalent arrhythmia, is often associated with enhanced inflammatory response. Emerging evidence points to a causal role of inflammatory signaling pathways in the evolution of atrial electrical, calcium handling and structural remodeling, which create the substrate of AF development. In this review, we discuss the clinical evidence supporting the association between inflammatory indices and AF development, the molecular and cellular mechanisms of AF, which appear to involve multiple canonical inflammatory pathways, and the potential of anti-inflammatory therapeutic approaches in AF prevention/treatment.

Reduction of Vascular Inflammation, LDL-C, or Both for the Protection from Cardiovascular Events?

BACKGROUND

Low density lipoprotein cholesterol (LDL-C) and low grade arterial inflammation are key pathogenic factors for atherosclerosis and its manifestation, cardiovascular disease (CVD).

OBJECTIVE

In this narrative review we assessed if decreasing LDL-C levels or inflammation or both is more effective in reducing CVD events.

RESULTS

In the Scandinavian Simvastatin Survival Study (4S), all statin trials of the 90s' and the Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER) the benefit came from the LDL-C reduction. In the GREak and Atorvastatin Coronary heart disease Evaluation (GREACE), the Treating to New Targets (TNT), and the Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trials both mechanisms in combination produced significant benefits. In the Atorvastatin for Reduction of MYocardial Damage during Angioplasty (ARMYDA) trials and the Canakinumab Antiinflammatory Thrombosis Outcome Study (CANTOS) with a human antibody targeting IL-1β with no lipid lowering effect, the reduction in arterial inflammation played the only beneficial role because there was no change in lipids levels.

CONCLUSION

Both LDL-C and inflammation reduction are beneficial to the reduction of CVD risk. However, canakinumab is a very expensive drug that only induced a 15% reduction in CVD events, thus drastically reducing the possibility for it to be used in clinical practice. Besides, canakinumab is associated with increased infections, some fatal. A potent statin with anti-inflammatory effects is probably the best choice for the majority of those needing hypolipidaemic drug therapy.

Regenerative Medicine and Immunomodulatory Therapy: Insights From the Kidney, Heart, Brain, and Lung

Regenerative medicine was initially focused on tissue engineering to replace damaged tissues and organs with constructs derived from cells and biomaterials. More recently, this field of inquiry has expanded into exciting areas of translational medicine modulating the body’s own endogenous processes, to prevent tissue damage in organs and to repair and regenerate these damaged tissues. This review will focus on recent insights derived from studies in which the manipulation of the innate immunologic system may diminish acute kidney injury and enhance renal repair and recovery without the progression to chronic kidney disease and renal failure. The manner in which these interventions may improve acute and chronic organ dysfunction, including the heart, brain, and lung, will also be reviewed.

The use of monocyte to HDL ratio to predict postoperative atrial fibrillation after aortocoronary bypass graft surgery

OBJECTIVE:

Postoperative atrial fibrillation (POAF) is a frequent and serious complication after aortocoronary bypass graft (ACBG) surgery and one that, unfortunately, increases morbidity and mortality. Postoperative stroke, hemodynamic instability, renal failure, infection, need for inotropic agent and coronary unit are complications caused by POAF. Inflammation and oxidative stress are among several mechanisms that contribute to pathogenesis of POAF. Monocyte to HDL (M/H) ratio is a newly defined parameter of both inflammation and oxidative stress. In this study, M/H ratio was investigated as predictor of POAF after ACBG surgery.

METHODS:

Total of 311 patients who underwent ACBG surgery were included in the study. Blood samples for analysis of routine biochemistry and lipid panel were obtained from the patients on the morning of ACBG surgery after 12 hours of fasting. Patients were continuously monitored for occurrence of POAF throughout hospitalization.

RESULTS:

POAF was observed in 71 patients following ACBG operation. M/H ratio was significantly higher in POAF(+) group compared with POAF(-) group (p<0.001). Median age of POAF(+) patients was 62.0±10.1 years, which was significantly higher than mean age of POAF(-) patients. Other atrial fibrillation (AF) risk factors, such as hypertension, diabetes mellitus, smoking, and alcohol consumption, were similar between groups. Potassium level was statistically lower in POAF(+) group compared with POAF(-) group (p=0.01).

CONCLUSION:

M/H ratio is an indicator of inflammation and oxidative stress, both of which play important role in pathogenesis of AF. M/H ratio was found be statistically significantly higher in POAF(+) patients than in POAF(-) patients.

Circulating intermediate CD14++CD16+monocytes are increased in patients with atrial fibrillation and reflect the functional remodelling of the left atrium

AIMS

A recent large clinical study demonstrated the association between intermediate CD14++CD16+monocytes and cardiovascular events. However, whether that monocyte subset contributes to the pathogenesis of atrial fibrillation (AF) has not been clarified. We compared the circulating monocyte subsets in AF patients and healthy people, and investigated the possible role of intermediate CD14++CD16+monocytes in the pathophysiology of AF.

METHODS AND RESULTS

This case-control study included 44 consecutive AF patients without systemic diseases referred for catheter ablation at our hospital, and 40 healthy controls. Patients with systemic diseases, including structural heart disease, hepatic or renal dysfunction, collagen disease, malignancy, and inflammation were excluded. Monocyte subset analyses were performed (three distinct human monocyte subsets: classical CD14++CD16-, intermediate CD14++CD16+, and non-classical CD14+CD16++monocytes). We compared the monocyte subsets and evaluated the correlation with other clinical findings. A total of 60 participants (30 AF patients and 30 controls as an age-matched group) were included after excluding 14 AF patients due to inflammation. Atrial fibrillation patients had a higher proportion of circulating intermediate CD14++CD16+monocytes than the controls (17.0 ± 9.6 vs. 7.5 ± 4.1%, P < 0.001). A multivariable logistic regression analysis demonstrated that only the proportion of intermediate CD14++CD16+monocytes (odds ratio: 1.316; 95% confidence interval: 1.095-1.582, P = 0.003) was independently associated with the presence of AF. Intermediate CD14++CD16+monocytes were negatively correlated with the left atrial appendage flow during sinus rhythm (r= -0.679, P = 0.003) and positively with the brain natriuretic peptide (r = 0.439, P = 0.015).

CONCLUSION

Intermediate CD14++CD16+monocytes might be closely related to the pathogenesis of AF and reflect functional remodelling of the left atrium.

Monocytes increase human cardiac myofibroblast-mediated extracellular matrix remodeling through TGF-β1

Following myocardial infarction (MI), cardiac myofibroblasts remodel the extracellular matrix (ECM), preventing mechanical complications. However, prolonged myofibroblast activity leads to dysregulation of the ECM, maladaptive remodeling, fibrosis, and heart failure (HF). Chronic inflammation is believed to drive persistent myofibroblast activity; however, the mechanisms are unclear. We assessed the influence of peripheral blood monocytes on human cardiac myofibroblast activity in a three-dimensional (3D) ECM microenvironment. Human cardiac myofibroblasts isolated from surgical biopsies of the right atrium and left ventricle were seeded into 3D collagen matrices. Peripheral blood monocytes were isolated from healthy human donors and cocultured with myofibroblasts. Monocytes increased myofibroblast activity measured by collagen gel contraction (baseline: 57.6 ± 5.9% vs. coculture: 65.2 ± 7.1% contraction; P < 0.01) and increased local ECM remodeling quantified by confocal microscopy. Under coculture conditions that allow indirect cellular interaction via paracrine factors but prevent direct cell-cell contact, monocytes had minimal effects on myofibroblast activity (17.9 ± 11.1% vs. 6.4 ± 7.0% increase, respectively; P < 0.01). When cells were cultured under direct contact conditions, multiplex analysis of the coculture media revealed an increase in the paracrine factors TGF-β1 and matrix metalloproteinase 9 compared with baseline (122.9 ± 10.1 pg/ml and 3,496.0 ± 190.4 pg/ml, respectively, vs. 21.5 ± 16.3 pg/ml and 183.3 ± 43.9 pg/ml; P < 0.001). TGF-β blockade abolished the monocyte-induced increase in cardiac myofibroblast activity. These data suggest that direct cell-cell interaction between monocytes and cardiac myofibroblasts stimulates TGF-β-mediated myofibroblast activity and increases remodeling of local matrix. Peripheral blood monocyte interaction with human cardiac myofibroblasts stimulates myofibroblast activity through release of TGF-β1. These data implicate inflammation as a potential driver of cardiac fibrosis.

Atrial Fibrillation, Neurocognitive Decline and Gene Expression After Cardiopulmonary Bypass

OBJECTIVE

Atrial fibrillation and neurocognitive decline are common complications after cardiopulmonary bypass. By utilizing genomic microarrays we investigate whether gene expression is associated with postoperative atrial fibrillation and neurocognitive decline.

METHODS

Twenty one cardiac surgery patients were prospectively matched and underwent neurocognitive assessments pre-operatively and four days postoperatively. The whole blood collected in the pre-cardiopulmonary bypass, 6 hours after-cardiopulmonary bypass, and on the 4^th postoperative day was hybridized to Affymetrix Gene Chip U133 Plus 2.0 Microarrays. Gene expression in patients who developed postoperative atrial fibrillation and neurocognitive decline (n=6; POAF+NCD) was compared with gene expression in patients with postoperative atrial fibrillation and normal cognitive function (n=5; POAF+NORM) and patients with sinus rhythm and normal cognitive function (n=10; SR+NORM). Regulated genes were identified using JMP Genomics 4.0 with a false discovery rate of 0.05 and fold change of >1.5 or <-1.5.

RESULTS

Eleven patients developed postoperative atrial fibrillation. Six of these also developed neurocognitive decline. Of the 12 patients with sinus rhythm, only 2 developed neurocognitive decline. POAF+NCD patients had unique regulation of 17 named genes preoperatively, 60 named genes six hours after cardiopulmonary bypass, and 34 named genes four days postoperatively (P<0.05) compared with normal patients. Pathway analysis demonstrated that these genes are involved in cell death, inflammation, cardiac remodeling and nervous system function.

CONCLUSION

Patients who developed postoperative atrial fibrillation and neurocognitive decline after cardiopulmonary bypass may have differential genomic responses compared to normal patients and patients with only postoperative atrial fibrillation, suggesting common pathophysiology for these conditions. Further exploration of these genes may provide insight into the etiology and improvements of these morbid outcomes.

The potential of the novel leukocyte removal filter in cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is indispensable for cardiac surgery but leads to systemic inflammatory responses and leukocyte activation, possibly due to blood contact with the surface of the CPB unit, surgical, ischemic reperfusion injury, etc. Systemic inflammatory responses during CPB result in increased morbidity and mortality. Activation of leukocytes is an important part of this process and directly contributes to coagulopathy and hemorrhage. This inflammatory response may contribute to the development of postoperative complications, including myocardial dysfunction, respiratory failure, renal and neurologic dysfunction, altered liver function and ultimately, multiple organ failure. Various pharmacologic and mechanical strategies have been developed to minimize the systemic inflammatory response during CPB. For example, leukocyte removal filters were developed in the 1990s for incorporation into the CPB circuit. However, studies of this approach have yielded conflicting findings. The purpose of this was to review the studies of a novel leukocyte removal filter in patients undergoing CPB.

Inflammation, oxidative stress and postoperative atrial fibrillation in cardiac surgery

Postoperative atrial fibrillation (POAF) is a common complication of cardiac surgery that occurs in up to 60% of patients. POAF is associated with increased risk of cardiovascular mortality, stroke and other arrhythmias that can impact on early and long term clinical outcomes and health economics. Many factors such as disease-induced cardiac remodelling, operative trauma, changes in atrial pressure and chemical stimulation and reflex sympathetic/parasympathetic activation have been implicated in the development of POAF. There is mounting evidence to support a major role for inflammation and oxidative stress in the pathogenesis of POAF. Both are consequences of using cardiopulmonary bypass and reperfusion following ischaemic cardioplegic arrest. Subsequently, several anti-inflammatory and antioxidant drugs have been tested in an attempt to reduce the incidence of POAF. However, prevention remains suboptimal and thus far none of the tested drugs has provided sufficient efficacy to be widely introduced in clinical practice. A better understanding of the cellular and molecular mechanisms responsible for the onset and persistence of POAF is needed to develop more effective prediction and interventions.

Hemoglobin-associated oxidative stress in the pericardial compartment of postoperative cardiac surgery patients

Atherosclerosis and valvular heart disease often require treatment with corrective surgery to prevent future myocardial infarction, ischemic heart disease, and heart failure. Mechanisms underlying the development of the associated complications of surgery are multifactorial and have been linked to inflammation and oxidative stress, classically as measured in the blood or plasma of patients. Postoperative pericardial fluid (PO-PCF) has not been investigated in depth with respect to the potential to induce oxidative stress. This is important because cardiac surgery disrupts the integrity of the pericardial membrane surrounding the heart and causes significant alterations in the composition of the pericardial fluid (PCF). This includes contamination with hemolyzed blood and high concentrations of oxidized hemoglobin, which suggests that cardiac surgery results in oxidative stress within the pericardial space. Accordingly, we tested the hypothesis that PO-PCF is highly pro-oxidant and that the potential interaction between inflammatory cell-derived hydrogen peroxide with hemoglobin is associated with oxidative stress. Blood and PCF were collected from 31 patients at the time of surgery and postoperatively from 4 to 48 h after coronary artery bypass grafting, valve replacement, or valve repair (mitral or aortic). PO-PCF contained high concentrations of neutrophils and monocytes, which are capable of generating elevated amounts of superoxide and hydrogen peroxide through the oxidative burst. In addition, PO-PCF primed naive neutrophils resulting in an enhanced oxidative burst upon stimulation. The PO-PCF also contained increased concentrations of cell-free oxidized hemoglobin that was associated with elevated levels of F2α isoprostanes and prostaglandins, consistent with both oxidative stress and activation of cyclooxygenase. Lastly, protein analysis of the PO-PCF revealed evidence of protein thiol oxidation and protein carbonylation. We conclude that PO-PCF is highly pro-oxidant and speculate that it may contribute to the risk of postoperative complications.

Circulating cardiac biomarkers and postoperative atrial fibrillation in the OPERA trial

BACKGROUND

Postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery and predicts increased morbidity and mortality. Identification of patients at high risk of POAF with the help of circulating biomarkers may enable early preventive treatment but data are limited, especially in contemporary surgical patients.

METHODS

Plasma concentrations of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT) were measured at enrollment, on the morning of cardiac surgery, at end surgery, and 2 days postsurgery in 562 patients undergoing cardiac surgery, randomized to perioperative supplementation with oral fish oil or placebo in the Omega-3 Fatty Acids for Prevention of Post-Operative Atrial Fibrillation trial (OPERA). The primary endpoint was incident POAF lasting ≥ 30 s, centrally adjudicated and confirmed electrocardiographically.

RESULTS

Higher levels of NT-proBNP and hs-cTnT before surgery were associated with older age, renal or cardiac dysfunction and EuroSCORE. NT-proBNP peaked on postoperative day 2 (2172 [1238-3758] ng/L, median [Q1-Q3]), while hs-cTnT peaked at the end of surgery (373 [188-660] ng/L). Fish oil supplementation did not alter the time course of the cardiac biomarkers (P > 0.05). Concentrations of NT-proBNP or hs-cTnT, on the morning of surgery, or changes in their level between morning of surgery and postsurgery, were not significantly associated with POAF after adjustment for clinical and surgical characteristics.

CONCLUSION

Among patients undergoing cardiac surgery, NT-proBNP and hs-cTnT are related to clinical and surgical characteristics, have different perioperative time courses but are not independently associated with risk of POAF.

Comparison of rosuvastatin versus atorvastatin for preventing postoperative atrial fibrillation

BACKGROUND

Postoperative atrial fibrillation (AF) following cardiac surgery is associated with an increased risk of stroke, prolonged hospitalization, and increased costs. Statin therapy is associated with a lower incidence of postoperative AF. We aimed to compare the preventive effects of rosuvastatin and atorvastatin on postoperative AF.

METHODS

This study included 168 patients undergoing elective cardiac surgery with cardiopulmonary bypass. Patients were divided into 2 groups according to treatment of statin. Group 1 (n = 96) was patients receiving atorvastatin, and group 2 (n = 72) was patients receiving rosuvastatin. Postoperative electrocardiographs (ECGs) and telemetry strips were examined for AF within postoperative period during hospitalization.

RESULTS

The incidences of postoperative AF were 17.9% (n = 17) in group 1 and 22.2% (n = 16) in group 2 (P = .48). Left ventricular end-diastolic diameter (LVEDD) and ejection fraction (EF) were not different between groups. Incidence of diabetes, hypertension, hyperlipidemia, smoking, myocardial infarction in past medical history, family history of atherosclerosis, male sex, drug use, and perioperative features were similar between groups.

CONCLUSIONS

The present study revealed that preoperative rosuvastatin or atorvastatin treatment did not have a different effect in preventing postoperative AF.

Post-operative atrial fibrillation: a maze of mechanisms

Post-operative atrial fibrillation (POAF) is one of the most frequent complications of cardiac surgery and an important predictor of patient morbidity as well as of prolonged hospitalization. It significantly increases costs for hospitalization. Insights into the pathophysiological factors causing POAF have been provided by both experimental and clinical investigations and show that POAF is ‘multi-factorial’. Facilitating factors in the mechanism of the arrhythmia can be classified as acute factors caused by the surgical intervention and chronic factors related to structural heart disease and ageing of the heart. Furthermore, some proarrhythmic mechanisms specifically occur in the setting of POAF. For example, inflammation and beta-adrenergic activation have been shown to play a prominent role in POAF, while these mechanisms are less important in non-surgical AF. More recently, it has been shown that atrial fibrosis and the presence of an electrophysiological substrate capable of maintaining AF also promote the arrhythmia, indicating that POAF has some proarrhythmic mechanisms in common with other forms of AF. The clinical setting of POAF offers numerous opportunities to study its mechanisms. During cardiac surgery, biopsies can be taken and detailed electrophysiological measurements can be performed. Furthermore, the specific time course of POAF, with the delayed onset and the transient character of the arrhythmia, also provides important insight into its mechanisms.

This review discusses the mechanistic interaction between predisposing factors and the electrophysiological mechanisms resulting in POAF and their therapeutic implications.

Vagal nerve stimulation in prevention and management of coronary heart disease

Coronary heart disease (CHD) that is due to atherosclerosis is associated with low-grade systemic inflammation. Congestive cardiac failure and arrhythmias that are responsible for mortality in CHD can be suppressed by appropriate vagal stimulation that is anti-inflammatory in nature. Acetylcholine, the principal vagal neurotransmitter, is a potent anti-inflammatory molecule. Polyunsaturated fatty acids (PUFAs) augment acetylcholine release, while acetylcholine can enhance the formation of prostacyclin, lipoxins, resolvins, protectins and maresins from PUFAs, which are anti-inflammatory and anti-arrhythmic molecules. Furthermore, plasma and tissue levels of PUFAs are low in those with CHD and atherosclerosis. Hence, vagal nerve stimulation is beneficial in the prevention of CHD and cardiac arrhythmias. Thus, measurement of catecholamines, acetylcholine, various PUFAs, and their products lipoxins, resolvins, protectins and maresins in the plasma and peripheral leukocytes, and vagal tone by heart rate variation could be useful in the prediction, prevention and management of CHD and cardiac arrhythmias.

Impact of circulating monocyte CD36 level on atrial fibrillation and subsequent catheter ablation

BACKGROUND

Inflammation, an important mechanism in the pathogenesis of atrial fibrillation (AF), can be regulated by CD36 in monocytes.

OBJECTIVE

The purpose of this study was to test the hypothesis that CD36 in monocytes contributes to the pathogenesis of AF.

METHODS

A prospective study that enrolled 87 patients with AF and 70 without AF was conducted.

RESULTS

Compared to patients without AF, patients with AF had monocytes with a lower level of CD36 protein, which correlated with left atrial diameter, left atrial emptying fraction, and left atrial mean voltage. In AF patients after catheter ablation, Kaplan-Meier analysis showed that the sinus rhythm maintenance rate was higher in patients with high CD36 levels. Low CD36 level was an independent predictor of recurrence. After successful ablation, the CD36 level increased by 57%, reaching that of control patients. CD36 level was not correlated with the level of high-sensitivity C-reactive protein. Analysis of mRNA levels from a buffy coat revealed that AF patients had lower CD36 and interleukin-10 levels and higher peroxisome proliferator-activated receptor-γ and tumor necrosis factor-α levels, with CD36 level positively correlated with interleukin-10 level but inversely correlated with peroxisome proliferator-activated receptor-γ and tumor necrosis factor-α levels.

CONCLUSION

Low CD36 levels in circulating monocytes were associated with AF occurrence and predicted recurrence after catheter ablation. The link between CD36 and AF identified a novel AF-related inflammatory pathway.

Lipoxin A4 may function as an endogenous anti-arrhythmic molecule

Cardiac arrhythmias cause significant morbidity and mortality in patients with coronary heart disease, hypertension, and congestive cardiac failure and in the elderly. Inflammation, oxidative injury, altered myocyte metabolism, extracellular matrix remodeling and fibrosis initiate and perpetuate cardiac arrhythmias, especially atrial fibrillation. Enhanced myeloperoxidase (MPO) activity by infiltrating activated leukocytes could bind to myocardial cells and cause fibrosis resulting in the initiation and progression of arrhythmias. Supplementation of eicosapentaenoic and docosahexaenoic acids (EPA and DHA, respectively) suppresses arrhythmias. EPA and DHA form precursors to anti-inflammatory lipid molecules: lipoxins, resolvins, protectins and maresins that are known to suppress inflammation, have anti-fibrotic actions and inhibit MPO activity. Hence, it is likely that leukocyte and/or myocardial deficiency of EPA and DHA and consequent reduced formation of lipoxins, resolvins, protectins and maresins enhance inflammation and MPO activity that leads to myocardial damage and fibrosis and initiation and progression of cardiac arrhythmias. Based on these evidences, I propose that lipoxins, resolvins and protectins function as endogenous anti-arrhythmic molecules and their stable synthetic analogs could be useful in the management of cardiac arrhythmias.

Preoperative n-3 polyunsatured fatty acids are associated with a decrease in the incidence of early atrial fibrillation following cardiac surgery

BACKGROUND

Atrial fibrillation (AF) after cardiac surgery is associated with increased mortality, morbidity, and expenditure. Controversial data exist on possible preventive effects of n-3 polyunsatured fatty acids (PUFAs) against postoperative AF. We investigated whether preoperative PUFA therapy is effective in reducing AF after cardiac surgery during the surgical hospitalization and/or the cardiac rehabilitation period.

METHODS

Over a 4-year period, 530 patients (363 men, 68.5%) with a mean age of 66.4 +/- 10.9 years, undergoing cardiac surgery were monitored for ''early AF'' and ''late AF'' defined as AF documented in the surgical department or during the rehabilitation program, respectively.

RESULTS

The overall incidence of early AF in the whole study sample was 44.7%, whereas late AF occurred in 14.7% patients. Patients with AF had a longer length of hospital and rehabilitation stay (10.4 +/- 9.8 vs 9.5 +/- 9.2 days, P = .025 and 24.2 +/- 15.3 vs 21.1 +/- 8.3 days, P = .008, respectively). Early AF occurred in 31.0% of the patients with preoperative PUFAs compared with 47.3% of those without them (P = .006). Conversely, late AF was not influenced by preoperative PUFA regimen (11.9% vs 15.2%, P = .43). Preoperative PUFAs were independently associated with a 46% reduction in risk of early AF development (OR 0.54, 95% CI 0.31-0.92), after propensity score analysis.

CONCLUSION

Preoperative PUFA therapy is associated with a decreased incidence of early AF after cardiac surgery but not late AF. Patients undergoing cardiac surgery may benefit from a preventive PUFA approach.