n-3 polyunsaturated fatty acids prevents atrial fibrillation by inhibiting inflammation in a canine sterile pericarditis model

Soluble PILRα: A novel plasma biomarker for atrial fibrillation progression and recurrence after catheter ablation

BACKGROUND

We aimed to identify plasma biomarkers of atrial fibrillation (AF) progression and recurrence after catheter ablation.

METHODS

Using AF gene profiling data from GEO database, a weighted gene co-expression network analysis (WGCNA) was conducted to determine the most significant module and hub genes associated with AF. Subsequently, 318 consecutively admitted patients who had undergone radiofrequency catheter ablation were enrolled in this study.

RESULTS

WGCNA results revealed that paired immunoglobulin-like type 2 receptor alpha (PILRA) was the only black module gene highly correlated with clinical traits. Plasma soluble PILRα (sPILRα) levels were elevated in patients with AF and significantly elevated in patients with persistent versus paroxysmal AF (4.64 ± 2.74 vs. 3.04 ± 1.56 ng/mL, p < 0.001). Elevated sPILRα level was an independent risk factor for AF progression even after adjusting for traditional factors (adjusted odds ratio: 3.06, 95 % confidence interval [CI]: 1.88-5.27, p < 0.001) and AF recurrence after catheter ablation in patients with persistent AF (adjusted hazards ratio: 4.41, 95 % CI: 1.22-15.92, p = 0.023).

CONCLUSIONS

WGCNA screening of GEO microarray gene profiling data showed PILRA expression levels to be correlated with AF progression and recurrence after catheter ablation in patients with persistent AF.

The neutrophil-to-lymphocyte ratio is a potential biomarker for the occurrence of atrial fibrillation in patients with obstructive sleep apnea: A BIOMARKER OF AF IN OSA PATIENTS

BACKGROUND

Obstructive sleep apnea (OSA) affects the occurrence of atrial fibrillation (AF) and usually coexists with AF. Chronic inflammation has been identified as an important factor in the development of AF, and the neutrophil-to-lymphocyte ratio (NLR) has been identified as a biomarker that positively correlates with the degree of inflammation. However, little information regarding how NLR correlates with AF in OSA patients.

METHODS

Our study enrolled 368 patients with OSA between September 2018 and April 2023. All data were collected after admission. Independently associated factors were assessed by multivariate logistic regression and then constructed a nomogram to predict AF risk. Nomogram's calculation model was evaluated using receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA). The correlation between CHA2DS2-VASc scores and NLR was assessed using Spearman correlation.

RESULTS

Multivariate logistic regression showed that high level log-transformed NLR (OR, 1.664; 95% CI, 1.026-2.699; P = 0.039) was independently associated with the presence of AF in patients with OSA. The concordance index (0.817, 95% CI, 0.770-0.864), ROC curve, calibration curve, and DCA of the nomogram indicated this model had well clinical utility. Also, the nomogram's calculation model could identify patients who are at a higher risk of developing AF, and the CHA2DS2-VASc score was positively correlated with NLR in patients with AF (P < 0.05).

CONCLUSION

The elevated NLR may serve as a promising biomarker for assessing the risk of AF in individuals with OSA. The nomogram's calculation model may be utilized as a tool to estimate the probability of AF occurrence in OSA patients.

Inflammatory signalling in atrial cardiomyocytes: a novel unifying principle in atrial fibrillation pathophysiology

Inflammation has been implicated in atrial fibrillation (AF), a very common and clinically significant cardiac rhythm disturbance, but its precise role remains poorly understood. Work performed over the past 5 years suggests that atrial cardiomyocytes have inflammatory signalling machinery - in particular, components of the NLRP3 (NACHT-, LRR- and pyrin domain-containing 3) inflammasome - that is activated in animal models and patients with AF. Furthermore, work in animal models suggests that NLRP3 inflammasome activation in atrial cardiomyocytes might be a sufficient and necessary condition for AF occurrence. In this Review, we evaluate the evidence for the role and pathophysiological significance of cardiomyocyte NLRP3 signalling in AF. We first summarize the evidence for a role of inflammation in AF and review the biochemical properties of the NLRP3 inflammasome, as defined primarily in studies of classic inflammation. We then briefly consider the broader evidence for a role of inflammatory signalling in heart disease, particularly conditions that predispose individuals to develop AF. We provide a detailed discussion of the available information about atrial cardiomyocyte NLRP3 inflammasome signalling in AF and related conditions and evaluate the possibility that similar signalling might be important in non-myocyte cardiac cells. We then review the evidence on the role of active resolution of inflammation and its potential importance in suppressing AF-related inflammatory signalling. Finally, we consider the therapeutic potential and broader implications of this new knowledge and highlight crucial questions to be addressed in future research.

Myeloperoxidase in the pericardial fluid improves the performance of prediction rules for postoperative atrial fibrillation

OBJECTIVES

After surgery, inflammation is a prominent factor influencing postoperative atrial fibrillation. Myeloperoxidase is a major contributor to inflammatory responses after surgical tissue damage. We evaluated whether myeloperoxidase is associated with postoperative atrial fibrillation clinically and in an animal model.

METHODS

This prospective cohort study included patients undergoing isolated coronary artery bypass grafting. Myeloperoxidase concentrations in blood and pericardial fluid were determined at baseline and 6, 12, and 18 hours after coronary artery bypass grafting. Myeloperoxidase activity in blood, pericardial fluid, and atrium were also evaluated in a canine coronary artery bypass grafting model. Electrophysiologic, histologic, and immunohistochemistry analyses were performed to explore underlying mechanisms.

RESULTS

Postoperative atrial fibrillation occurred in 45 of 137 patients (32.8%). Patients with postoperative atrial fibrillation had significantly higher serum and pericardial myeloperoxidase levels. Individual clinical and surgical factors had moderate predictive value (area under the curve, 0.760) for postoperative atrial fibrillation. Discrimination improved remarkably when myeloperoxidase was combined with other parameters (area under the curve, 0.901). Pericardial myeloperoxidase at 6 hours postoperatively was the strongest independent predictor of postoperative atrial fibrillation (odds ratio, 19.215). The rate of postoperative atrial fibrillation increased exponentially across pericardial myeloperoxidase grades. Compared with controls, coronary artery bypass grafting-treated dogs showed higher atrial fibrillation vulnerability and maintenance, shorter atrial effective refractory period, attenuated connexin 43 expression, and increased myocardial and pericardial myeloperoxidase activity. Connexin 43 expression and atrial effective refractory period were strongly negatively correlated with myocardial and pericardial myeloperoxidase activity.

CONCLUSIONS

Myeloperoxidase is linked to postoperative atrial fibrillation, and the ability to predict postoperative atrial fibrillation was remarkably improved by adding pericardial myeloperoxidase. Myeloperoxidase-related atrial structural and electrical remodeling is a physiologic substrate for this arrhythmia.

Immune infiltration and immunophenotyping in atrial fibrillation

Atrial fibrillation (AF) is a relatively common arrhythmia in clinical practice. Although significant progress has been achieved in the treatment of AF and its associated complications, research on AF prevention lags behind, mainly due to the lack of a deep understanding of AF pathogenesis. In recent years, as our knowledge has grown, the role of the inflammatory/immune response in the occurrence and progression of AF has gradually gained attention. In this paper, based on existing gene expression data in the Gene Expression Omnibus database, a detailed description of immune infiltration status in AF is presented using a series of analytical methods, including differential analysis, Gene Ontology categorization, Kyoto Encyclopedia of Genes and Genomes enrichment analysis, and weighted gene coexpression network analysis, and analysis tools such as CIBERSORTx and Cytoscape. Several new AF/immune infiltrations-related signature genes were identified, and the AF/immune infiltration pathology was classified based on these immune signature genes, thus providing novel insights into the pathogenesis of AF based on the inflammatory response.

Analysis of infiltrated immune cells in left atriums from patients with atrial fibrillation and identification of circRNA biomarkers for postoperative atrial fibrillation

Background: Atrial fibrillation (AF) increases the risk of stroke and heart failure. Postoperative AF (POAF) increases the risk of mortality after cardiac surgery. This study aims to explore mechanisms underlying AF, analyze infiltration of immune cells in left atrium (LA) from patients with AF, and identify potential circular RNA (circRNA) biomarkers for POAF. Methods: Raw data of GSE797689, GSE115574, and GSE97455 were downloaded and processed. AF-related gene co-expression network was constructed using weighted gene correlation network analysis and enrichment analysis of genes in relevant module was conducted. Gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were applied to investigate pathways significantly enriched in AF group. Infiltration of immune cells was analyzed using single-sample GSEA. Differentially expressed genes (DEGs) between patients with or without AF were identified and competing endogenous RNA (ceRNA) networks of DEGs were constructed. To screen biomarkers for POAF, differentially expressed circRNAs (DEcircRNAs) between patients with or without POAF were identified. Intersection between DEcircRNAs and circRNAs in ceRNA networks of DEGs were extracted and circRNAs in the intersection were further screened using support vector machine, random forest, and neural network to identify biomarkers for POAF. Results: Three modules were found to be relevant with AF and enrichment analysis indicated that genes in these modules were enriched in synthesis of extracellular matrix and inflammatory response. The results of GSEA and GSVA suggested that inflammatory response-related pathways were significantly enriched in AF group. Immune cells like macrophages, mast cells, and neutrophils were significantly infiltrated in LA tissues from patients with AF. The expression levels of immune genes such as CHGB, HLA-DRA, LYZ, IGKV1-17 and TYROBP were significantly upregulated in patients with AF, which were correlated with infiltration of immune cells. ceRNA networks of DEGs were constructed and has_circ_0006314 and hsa_circ_0055387 were found to have potential predictive values for POAF. Conclusion: Synthesis of extracellular matrix and inflammatory response were main processes involved in development and progression of AF. Infiltration of immune cells was significantly different between patients with or without AF. Has_circ_0006314 and hsa_circ_0055387 were found to have potential predictive values for POAF.

Prednisone Ameliorates Atrial Inflammation and Fibrosis in Atrial Tachypacing Dogs

Atrial inflammation and fibrosis have long been considered culprits in the development of atrial fibrillation (AF). Prior clinical studies showed that corticosteroid therapy is beneficial in patients with AF. Here we sought to determine whether prednisone treatment prevents atrial tachypacing (ATP) induced atrial fibrosis.Dogs were randomized into the sham, ATP, ATP + low-dose prednisone (ALP), and ATP + high-dose prednisone (AHP) groups. After 6 days of recovery from surgery, dogs were subjected to ATP at 400 beats per minute for 4 weeks while being treated with prednisone (15 or 40 mg/day) or a placebo. Pacemakers were not activated in the sham group.Compared with the ATP group, the expression of collagen I, collagen III, α-smooth muscle actin, transforming growth factor-β1 and connective tissue growth factor were significantly reduced in the ALP and AHP groups. Fluorescence assays showed that reactive oxygen species formation in the right atrium was suppressed in the ALP and AHP groups compared with the ATP group. The protein level of NADPH oxidase 2 was reduced in the ALP and AHP groups' versus ATP group, while NOX4 and NOX5 were unchanged. ATP-induced downregulation of BH4 and eNOS uncoupling in the atria was partially restored in the prednisone-treated groups.Our study demonstrated that atrial fibrosis induced by ATP were suppressed by prednisone. Low-dose prednisone was also effective in suppressing the development of atrial fibrosis.

Electroimmunology and cardiac arrhythmia

Conduction disorders and arrhythmias remain difficult to treat and are increasingly prevalent owing to the increasing age and body mass of the general population, because both are risk factors for arrhythmia. Many of the underlying conditions that give rise to arrhythmia - including atrial fibrillation and ventricular arrhythmia, which frequently occur in patients with acute myocardial ischaemia or heart failure - can have an inflammatory component. In the past, inflammation was viewed mostly as an epiphenomenon associated with arrhythmia; however, the recently discovered inflammatory and non-canonical functions of cardiac immune cells indicate that leukocytes can be arrhythmogenic either by altering tissue composition or by interacting with cardiomyocytes; for example, by changing their phenotype or perhaps even by directly interfering with conduction. In this Review, we discuss the electrophysiological properties of leukocytes and how these cells relate to conduction in the heart. Given the thematic parallels, we also summarize the interactions between immune cells and neural systems that influence information transfer, extrapolating findings from the field of neuroscience to the heart and defining common themes. We aim to bridge the knowledge gap between electrophysiology and immunology, to promote conceptual connections between these two fields and to explore promising opportunities for future research.

Anti-arrhythmic and anti-heart failure effects of low-level electrical stimulation on aortic root ventricular ganglionated plexi

BACKGROUND

It remains uncertain whether low-level electrical stimulation (LL-ES) of the ventricular ganglionated plexi (GP) improves heart function. This study investigated the anti-arrhythmic and anti-heart failure effects of LL-ES of the aortic root ventricular GP (ARVGP).

METHODS

Thirty dogs were divided randomly into control, drug, and LL-ES groups after performing rapid right ventricular pacing to establish a heart failure (HF) model. The inducing rate of arrhythmia; levels of bioactive factors influencing HF, including angiotensin II type I receptor (AT-1R), transforming growth factor-beta (TGF-β), matrix metalloproteinase (MMP), and phosphorylated extracellular signal-regulated kinase (p-ERK1/2); left ventricular stroke volume (LVSV), and left ventricular ejection fraction (LVEF)were measured after treatment with placebo, drugs, and LL-ES.

RESULTS

The inducing rate of atrial arrhythmia decreased from 60% in the control group to 50% in the drug group and 10% in the LL-ES group (p = .033 vs. drug group) after 1 week of treatment. The ventricular effective refractory period was prolonged from 139 ± 8 ms in the drug group to 166 ± 13 ms in the LL-ES group (p = .001). Compared to the drug group, the expressions of AT-1R, TGF-β, and MMP proteins were down-regulated in the LL-ES group, whereas that of p-ERK1/2 was significantly increased (all p = .001). Moreover, in the LL-ES group, LVSV increased markedly from 13.16 ± 0.22 to 16.86 ± 0.27 mL, relative to that in the drug group (p = .001), and LVEF increased significantly from 38.48% ± 0.53% to 48.94% ± 0.57% during the same time frame (p = .001).

CONCLUSION

Short-term LL-ES of ARVGP had both anti-arrhythmic and anti-inflammatory effects and contributed to the treatment of tachycardia-induced HF and its associated arrhythmia.

Postoperative Atrial Fibrillation: Features, Mechanisms, and Clinical Management

Advances in atrial fibrillation (AF) management, perioperative medicine, and surgical techniques have reignited an interest in postoperative AF (POAF). POAF results from the interaction among subclinical atrial substrate, surgery-induced substrate, and transient postoperative factors. Prophylaxis for POAF after cardiac surgery is well established but the indications for preoperative treatment in noncardiac surgery need further investigation. A rate-control strategy is adequate for most asymptomatic patients with POAF and anticoagulation should be initiated for POAF more than 48 to 72 hours postsurgery. Research is needed to improve evidence-based management of POAF and guide long-term management in view of the substantial late recurrence-rate.

Systematic review of pre-clinical therapies for post-operative atrial fibrillation

BACKGROUND

Post-operative atrial fibrillation (POAF) is a frequent cardiothoracic surgery complication that increases hospital stay, mortality and costs. Despite decades of research, there has been no systematic overview and meta-analysis of preclinical therapies for POAF in animal models.

METHODS

We performed a systematic search of MEDLINE and EMBASE from their inception through September 2020 to determine the effect of preclinical POAF therapies on primary efficacy outcomes using a prospectively registered protocol (CRD42019155649). Bias was assessed using the SYRCLE tool and CAMARADES checklist.

RESULTS

Within the 26 studies that fulfilled our inclusion criteria, we identified 4 prevention strategies including biological (n = 5), dietary (n = 2), substrate modification (n = 2), and pharmacological (n = 17) interventions targeting atrial substrate, cellular electrophysiology or inflammation. Only one study altered more than 1 pathophysiological mechanism. 73% comprised multiple doses of systemic therapies. Large animal models were used in 81% of the studies. Preclinical therapies altogether attenuated atrial fibrosis (SMD -2.09; 95% confidence interval [CI] -2.95 to -1.22; p < 0.00001; I2 = 47%), AF inducibility (RR 0.40; 95% CI 0.21 to 0.79; p = 0.008; I2 = 39%), and AF duration (SMD -2.19; 95% CI -3.05 to -1.32; p < 0.00001; I2 = 50%). However, all the criteria needed to evaluate the risk of bias was unclear for many outcomes and only few interventions were independently validated by more than 1 research group.

CONCLUSION

Treatments with therapies targeting atrial substrate, cellular electrophysiology or inflammation reduced POAF in preclinical animal models compared to controls. Improving the quality of outcome reporting, independently validating promising approaches and targeting complimentary drivers of POAF are promising means to improve the clinical translation of novel therapies for this highly prevalent and clinically meaningful disease.

Colchicine prevents atrial fibrillation promotion by inhibiting IL-1β-induced IL-6 release and atrial fibrosis in the rat sterile pericarditis model

A few clinical trials have recently reported the potential effect of colchicine in preventing post-operative atrial fibrillation (POAF) and early atrial fibrillation (AF) recurrence after catheter pulmonary vein isolation. However, the molecular mechanisms through which colchicine inhibits AF remain unclear. We aim to assess the anti-AF effect of colchicine in the rat sterile pericarditis (SP) model and to investigate its molecular mechanisms. SP was induced in Sprague-Dawley rats by the epicardial application of sterile talc. Treatment with colchicine or vehicle began 1 d before pericardiotomy. AF was induced by transesophageal burst pacing on day 3 after surgery. Treatment with colchicine reduced the duration of AF and the probability of induction of AF in SP rats. The dose of 0.5 mg kg^-1·day^-1 had the best effect. Such treatment also reduced neutrophil infiltration, the mRNA expression of IL-6, TGF-β, and TNF-α, atrial fibrosis, fibrosis related genes, and signal molecules (STAT3, P38, and AKT). Meanwhile, the release of IL-1β (4-24 h) and IL-6 (4-72 h) in atria after surgery was significantly inhibited by colchicine. In cultured rat cardiac fibroblasts, colchicine treatment inhibited IL-1β-induced expression of IL-6, which was accompanied by significantly decreased phosphorylation of P38, AKT, JNK, and NFκB. Interestingly, the supplementation of IL-6 abolished the anti-AF effect of colchicine in SP rats. Colchicine prevents AF in SP rats through the inhibition of IL-1β-induced IL-6 release and subsequent atrial fibrosis. However, further studies are required to investigate whether colchicine inhibits POAF through other mechanisms.

New-onset postoperative atrial fibrillation after heart surgery

BACKGROUND

New-onset postoperative atrial fibrillation (poAF) complicates approximately 20-60% of all cardiac surgical procedures and is associated with an increased periprocedural mortality and morbitity, prolonged hospital stay, increased costs, and worse long-term survival. Unfortunately multiple advances in surgery and perioperative care over the last two decades have not led to a reduction in the incidence of poAF or associated complications in the daily clinical practice.

METHODS

A narrative review of the available literature was performed.

RESULTS

An extensive review of the pathophysiology of poAF following cardiac surgery, clinical, and procedural risk-factors is provided, as well as prophylactic measures and treatment.

CONCLUSION

Multiple strategies to prevent and manage poAF following heart surgery already exist. Our hope is that this review will facilitate more rigorous testing of prevention strategies, implementation of prophylaxis regimens as well as optimal treatment of this common and serious complication.

Omega-3 Index and Anti-Arrhythmic Potential of Omega-3 PUFAs

Omega-3 polyunsaturated fatty acids (PUFAs), namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are permanent subjects of interest in relation to the protection of cardiovascular health and the prevention of the incidence of both ventricular and atrial arrhythmias. The purpose of this updated review is to focus on the novel cellular and molecular effects of omega-3 PUFAs, in the context of the mechanisms and factors involved in the development of cardiac arrhythmias; to provide results of the most recent studies on the omega-3 PUFA anti-arrhythmic efficacy and to discuss the lack of the benefit in relation to omega-3 PUFA status. The evidence is in the favor of omega-3 PUFA acute and long-term treatment, perhaps with mitochondria-targeted antioxidants. However, for a more objective evaluation of the anti-arrhythmic potential of omega-3 PUFAs in clinical trials, it is necessary to monitor the basal pre-interventional omega-3 status of individuals, i.e., red blood cell content, omega-3 index and free plasma levels. In the view of evidence-based medicine, it seems to be crucial to aim to establish new approaches in the prevention of cardiac arrhythmias and associated morbidity and mortality that comes with these conditions.

Signal Transducer and Activator of Transcription 3/MicroRNA-21 Feedback Loop Contributes to Atrial Fibrillation by Promoting Atrial Fibrosis in a Rat Sterile Pericarditis Model

Supplemental Digital Content is available in the text.

Background—

Postoperative atrial fibrillation is a frequent complication in cardiac surgery. The aberrant activation of signal transducer and activator of transcription 3 (STAT3) contributes to the pathogenesis of atrial fibrillation. MicroRNA-21 (miR-21) promotes atrial fibrosis. Recent studies support the existence of reciprocal regulation between STAT3 and miR-21. Here, we test the hypothesis that these 2 molecules might form a feedback loop that contributes to postoperative atrial fibrillation by promoting atrial fibrosis.

Methods and Results—

A sterile pericarditis model was created using atrial surfaces dusted with sterile talcum powder in rats. The inflammatory cytokines interleukin (IL)-1β, IL-6, transforming growth factor-β, and tumor necrosis factor-α, along with STAT3 and miR-21, were highly upregulated in sterile pericarditis rats. The inhibition of STAT3 by S3I-201 resulted in miR-21 downregulation, which ameliorated atrial fibrosis and decreased the expression of the fibrosis-related genes, α-smooth muscle actin, collagen-1, and collagen-3; reduced the inhomogeneity of atrial conduction; and attenuated atrial fibrillation vulnerability. Meanwhile, treatment with antagomir-21 decreased STAT3 phosphorylation, alleviated atrial remodeling, abrogated sterile pericarditis–induced inhomogeneous conduction, and prevented atrial fibrillation promotion. The culturing of cardiac fibroblasts with IL-6 resulted in progressively augmented STAT3 phosphorylation and miR-21 levels. S3I-201 blocked IL-6 induced the expression of miR-21 and fibrosis-related genes in addition to cardiac fibroblast proliferation. Transfected antagomir-21 decreased the IL-6–induced cardiac fibroblast activation and STAT3 phosphorylation. The overexpression of miR-21 in cardiac fibroblasts caused the upregulation of STAT3 phosphorylation, enhanced fibrosis-related genes, and increased cell numbers.

Conclusions—

Our results have uncovered a novel reciprocal loop between STAT3 and miR-21 that is activated after heart surgery and can contribute to atrial fibrillation.

Omega-3 polyunsaturated fatty acids in cardiac surgery patients: An updated systematic review and meta-analysis

BACKGROUND

Omega-3 polyunsaturated fatty acids (ω-3 PUFA) supplementation is an attractive therapeutic option for patients undergoing open-heart surgery due to their anti-inflammatory and anti-arrhythmic properties. Several randomized controlled trials (RCT) have found contradictory results for perioperative ω-3 PUFA administration. Therefore, we conducted an updated systematic review and meta-analysis evaluating the effects of perioperative ω-3 PUFA on some clinically important outcomes for cardiac surgery.

METHODS

A systematic literature search was conducted to find RCT evaluating clinical outcomes after ω-3 PUFA therapy in adult patients undergoing cardiac surgery. Intensive care unit (ICU) length of stay (LOS) was the primary outcome; secondary outcomes were hospital LOS, postoperative atrial fibrillation (POAF), mortality and duration of mechanical ventilation (MV). Predefined subgroup analysis and sensibility analysis were performed.

RESULTS

A total of 19 RCT including 4335 patients met inclusion criteria. No effect of ω-3 PUFA on ICU LOS was found (weighted mean difference WMD -2.95, 95% confidence interval, CI -10.28 to 4.39, P = 0.43). However, ω-3 PUFA reduced hospital LOS (WMD -1.37, 95% CI -2.41 to -0.33; P = 0.010) and POAF incidence (Odds Ratio OR = 0.78, 95% CI 0.68 to 0.90; P = 0.004). No effects were found on mortality or MV duration. Heterogeneity remained in subgroup analysis and we found a significant POAF reduction when ω-3 PUFA doses were administered to patients exposed to extra-corporeal circulation. Oral/enteral administration seemed to further reduce POAF.

CONCLUSIONS

In patients undergoing cardiac surgery, ω-3 PUFA supplementation by oral/enteral and parenteral route reduces hospital LOS and POAF. Nonetheless considerable clinical and statistical heterogeneity weaken our findings.

Ischemic Stroke after Heart Transplantation

Cerebrovascular complications after orthotopic heart transplantation (OHT) are more common in comparison with neurological sequelae subsequent to routine cardiac surgery. Ischemic stroke and transient ischemic attack (TIA) are more common (with an incidence of up to 13%) than intracranial hemorrhage (2.5%). Clinically, ischemic stroke is manifested by the appearance of focal neurologic deficits, although sometimes a stroke may be silent or manifests itself by the appearance of encephalopathy, reflecting a diffuse brain disorder. Ischemic stroke subtypes distribution in perioperative and postoperative period after OHT is very different from classical distribution, with different pathogenic mechanisms. Infact, ischemic stroke may be caused by less common and unusual mechanisms, linked to surgical procedures and to postoperative inflammation, peculiar to this group of patients. However, many strokes (40%) occur without a well-defined etiology (cryptogenic strokes). A silent atrial fibrillation (AF) may play a role in pathogenesis of these strokes and P wave dispersion may represent a predictor of AF. In OHT patients, P wave dispersion correlates with homocysteine plasma levels and hyperhomocysteinemia could play a role in the pathogenesis of these strokes with multiple mechanisms increasing the risk of AF. In conclusion, stroke after heart transplantation represents a complication with considerable impact not only on mortality but also on subsequent poor functional outcome.

The Current Role of Omega-3 Fatty Acids in the Management of Atrial Fibrillation

Background: The main dietary source of omega-3 polyunsaturated fatty acids (n-3 PUFA) is fish, which contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In the present manuscript, we aimed to review the current evidence regarding the clinical role of n-3 PUFA in the prevention of atrial fibrillation (AF) and the possible underlying mechanisms. Methods: A literature search based on PubMed listings was performed using “Omega-3 fatty acids” and “atrial fibrilation” as key search terms. Results: n-3 PUFA have been shown to attenuate structural atrial remodeling, prolong atrial effective refractory period through the prevention of reentry and suppress ectopic firing from pulmonary veins. Dietary fish intake has been found to have no effect on the incidence of AF in the majority of studies. Circulating DHA has been consistently reported to be inversely associated with AF risk, whereas EPA has no such effect. The majority of studies investigating the impact of n-3 PUFA supplementation on the incidence of AF following cardiac surgery reported no benefit, though most of them did not use n-3 PUFA pretreatment for adequate duration. Studies using adequate four-week pretreatment with n-3 PUFA before cardioversion of AF showed a reduction of the AF incidence. Conclusions: Although n-3 PUFA have antiarrhythmogenic properties, their clinical efficacy on the prevention of AF is not consistently supported. Further well-designed studies are needed to overcome the limitations of the existing studies and provide robust conclusions.

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.

Interleukin-17A contributes to the development of post-operative atrial fibrillation by regulating inflammation and fibrosis in rats with sterile pericarditis

Post-operative atrial fibrillation (AF) remains a common cause of morbidity. Increasing evidence indicates that inflammation and atrial fibrosis contribute to the pathogenesis of this condition. Interleukin (IL)-17A, a potent pro-inflammatory cytokine, has been implicated in the development of a number of cardiovascular diseases. However, its role in post-operative AF remains unknown. In the present study, sterile pericarditis (SP) was induced in rats by the epicardial application of sterile talc. AF was induced by transesophageal burst pacing. Western blot analysis was applied to quantify the expression of IL-17A. Quantitative PCR was used to detect the mRNA expression of IL-17A, IL-6, IL-1β, transforming growth factor-β1 (TGF-β1), collagen type 1 (Col-1), collagen type 3 (Col-3) and α-smooth muscle actin (α-SMA). Gelatin zymography and reverse gelatin zymography were used to quantify the levels of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). Histological analyses were performed to determine the extent of tissue inflammation and fibrosis. The rats with SP presented with a shorter refractoriness, a higher incidence and duration of AF, an enhanced susceptibility to developing AF, increased mRNA levels of AF-related pro-inflammatory cytokines (IL-6, IL-1β and TGF-β1), as well as marked atrial inflammation and fibrosis. The atrial IL-17A levels were elevated and correlated with the probability of developing AF. Treatment with anti-IL-17A monoclonal antibody decreased the levels of atrial IL-17A, prolonged refraction and markedly suppressed the development of AF. Simultaneously, inflammation and fibrosis were alleviated, which was further demonstrated by a decreased expression of AF-related pro-inflammatory cytokines, a down-regulation in fibrosis-related mRNA expression (Col-1, Col-3 and α-SMA) and by the decreased activity of MMP-2/9 and TIMPs. Thus, the findings of our study indicate that IL-17A may play a pathogenic role in post-operative AF by inducing inflammation and fibrosis in rats with SP.

Inflammation and the pathogenesis of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia. However, the development of preventative therapies for AF has been disappointing. The infiltration of immune cells and proteins that mediate the inflammatory response in cardiac tissue and circulatory processes is associated with AF. Furthermore, the presence of inflammation in the heart or systemic circulation can predict the onset of AF and recurrence in the general population, as well as in patients after cardiac surgery, cardioversion, and catheter ablation. Mediators of the inflammatory response can alter atrial electrophysiology and structural substrates, thereby leading to increased vulnerability to AF. Inflammation also modulates calcium homeostasis and connexins, which are associated with triggers of AF and heterogeneous atrial conduction. Myolysis, cardiomyocyte apoptosis, and the activation of fibrotic pathways via fibroblasts, transforming growth factor-β and matrix metalloproteases are also mediated by inflammatory pathways, which can all contribute to structural remodelling of the atria. The development of thromboembolism, a detrimental complication of AF, is also associated with inflammatory activity. Understanding the complex pathophysiological processes and dynamic changes of AF-associated inflammation might help to identify specific anti-inflammatory strategies for the prevention of AF.

Construction and analysis of correlation networks based on gas chromatography-mass spectrometry metabonomics data for lipopolysaccharide-induced inflammation and intervention with volatile oil from Angelica sinensis in rats

Angelica sinensis (AS) is a well-known important traditional Chinese medicine that yields a volatile oil with anti-inflammatory effects.

PI3K/AKT/PTEN pathway as a target for Crohn's disease therapy (Review)

The pathogenesis of inflammatory bowel disease (IBD), including Crohn's disease, is a subject of increasing interest. Loss-of-function mutations in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) are strong genetic factors linked to Crohn's disease, which eventually leads to an excessive mucosal inflammatory response directed against components of normal gut microbiota. Reactive oxygen species (ROS) play an important role in inflammation processes, as well as in transduction of signals from receptors for several cytokines, such as tumor necrosis factor α (TNFα). ROS activate nuclear factor-κB (NF-κB) via IκB kinase (IKK) through the PI3K/AKT/PTEN pathway. Therefore, this pathway is recognized to play a key role in Crohn's disease. Loss of function has been demonstrated to occur as an early event in a wide variety of diseases. Given this prevalent involvement in a number of diseases, the molecular development that modulates this pathway has been the subject of several studies. In addition, it has been the focus of extensive research and drug discovery activities. A better understanding of the molecular assemblies may reveal novel targets for the therapeutic development against Crohn's disease.

Role of Inflammation in Initiation and Perpetuation of Atrial Fibrillation: A Systematic Review of the Published Data

Inflammation has emerged as being strongly associated with AF initiation and perpetuation, including being implicated as a possible causal factor. Its role needs further elucidation to assist with the optimal prevention and treatment of AF using an individualized strategy. In the present review article the current published data linking inflammation to AF is summarized.

Effects of long-term ω-3 polyunsaturated fatty acid supplementation on paroxysmal atrial tachyarrhythmia burden in patients with implanted pacemakers: results from a prospective randomised study

BACKGROUND

Sino-atrial node disease and aging increase AF risk. We investigated if long-term fish oil supplementation reduces paroxysmal atrial tachycardia/fibrillation (AT/AF) burden in patients aged ≥60 years with sinoatrial node disease and dual chamber pacemakers.

METHODS

Following a run-in period of 6 months (p1) where AT/AF burden was logged,78 patients were randomised to control or fish oil group (total omega-3 6 g/d) and AT/AF burden evaluated after 6 months (p2; 39 controls, 39 fish oil) and 12 months (p3; 39 controls; 18 fish oil). A subset of 21 fish oil patients crossed over to controls in the final 6 months (crossover group).

RESULTS

Median AT/AF burden increased significantly in controls (1.5%, 3.2%, 4.3%, P<.001) but not in fish oil patients at 6 months (1.4% to 2%, P=.46) or those continuing for 12 months (1.5%, 0.98%, 1%, P=.16). Time to first episode of AT/AF >1 min was not significantly different between the groups (P=.9). There was a rebound increase in AT/AF burden in p3 in cross over patients (2.2% to 5.8%, P=.01) reaching a level similar to controls (crossover vs. controls, 5.8% vs. 4.3%, P=.63) and higher than those who continued fish oil for 12 months (crossover vs. continued intake 5.8% vs. 1.2%, P=.02). Fish oil patients had shorter duration episodes of AT/AF with no difference in frequency compared to controls.

CONCLUSION

Long-term fish oil supplementation did not suppress AT/AF burden but may have attenuated its temporal progression related to aging and sinus node disease.

Do Omega-3 Fatty Acids Decrease the Incidence of Atrial Fibrillation?

Although atrial fibrillation is a very common medical problem in general population and has a high incidence in the setting of open heart surgery, there are very few therapies to prevent occurrence or recurrence of atrial fibrillation. N-3 polyunsaturated fatty acids have been shown to change basic physiologic properties of the atrial tissue to make it less susceptible to atrial fibrillation. In this review, we first describe basic physiological mechanisms thought to be responsible for these changes and then discuss observational and interventional studies evaluating the use n-3 polyunsaturated fatty acids for primary and secondary prevention of atrial fibrillation in the general population, in subjects undergoing open heart surgery, and in special subgroups of patients.

The effects of omega-3 polyunsaturated fatty acids on cardiac rhythm: a critical reassessment

Although epidemiological studies provide strong evidence for an inverse relationship between omega-3 polyunsaturated fatty acids (n-3 PUFAs) and cardiac mortality, inconsistent and often conflicting results have been obtained from both animal studies and clinical prevention trials. Despite these heterogeneous results, some general conclusions can be drawn from these studies: 1) n-PUFAs have potent effects on ion channels and calcium regulatory proteins that vary depending on the route of administration. Circulating (acute administration) n-3 PUFAs affect ion channels directly while incorporation (long-term supplementation) of these lipids into cell membranes indirectly alter cardiac electrical activity via alteration of membrane properties. 2) n-3 PUFAs reduce baseline HR and increase HRV via alterations in intrinsic pacemaker rate rather than from changes in cardiac autonomic neural regulation. 3) n-3 PUFAs may be only effective if given before electrophysiological or structural remodeling has begun and have no efficacy against atrial fibrillation. 5) Despite initial encouraging results, more recent clinical prevention and animal studies have not only failed to reduce sudden cardiac death but actually increased mortality in angina patients and increased rather than decreased malignant arrhythmias in animal models of regional ischemia. 6) Given the inconsistent benefits reported in clinical and experimental studies and the potential adverse actions on cardiac rhythm noted during myocardial ischemia, n-3 PUFA must be prescribed with caution and generalized recommendations to increase fish intake or to take n-3 PUFA supplements need to be reconsidered.

Effects of high dose intravenous fish oil on human atrial electrophysiology: implications for possible anti- and pro-arrhythmic mechanisms in atrial fibrillation

BACKGROUND

Intravenous omega-3 polyunsaturated fatty acids (ω-3 PUFAs) may prevent atrial fibrillation (AF) inducibility and perpetuation in animal models. We examined the effect of high dose IV ω-3 PUFAs on human atrial electrophysiology.

METHODS AND RESULTS

We randomised 88 patients with no structural heart disease to receive saline (control group) or high dose IV ω-3 PUFA infusion prior to detailed atrial electrophysiologic evaluation. Biologically active components, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were measured in total lipids, free fatty acid and phospholipid (membrane incorporated) fraction pre and post infusion. Compared to pre-infusion values, EPA and DHA increased significantly in the total lipids and free fatty acid but were unchanged in the phospholipid fraction. IV ω-3 did not alter atrial refractory periods, however it slowed right, left and global atrial conduction (P<.05). Inducible AF was significantly less likely in ω-3 patients compared to controls (AF ≥ 5 min, 20% vs. 58%, P = .02) and was non-sustained (mean AF duration: 14s vs. 39 s, P<.001), however inducible and sustained atrial flutter was more common (≥ 5 min: 28% vs. 0%, P = .01). Organisation of AF into flutter was observed in a greater proportion of inductions in the ω-3 group (8.5% vs. 0.6%, P<.001).

CONCLUSIONS

IV ω-3 PUFAs (as free fatty acids) cause acute atrial conduction slowing, suppress AF inducibility, organise AF into atrial flutter and enhance atrial flutter inducibility. These findings provide a novel insight into potential anti and pro-arrhythmic mechanisms of fish oils in human AF.

A meta-analysis of omega-3 fatty acids and incidence of atrial fibrillation

OBJECTIVES

Atrial fibrillation (AF) is associated with higher health care costs. Although omega-3 (n-3) fatty acids have been associated with a decreased risk of coronary heart disease, their effects on the risk of AF are inconsistent. We therefore sought to review the relation between n-3 fatty acids and the risk of AF.

METHODS

Using an extensive online search, we conducted a meta-analysis of new onset incident/recurrent AF following exposure to fish/fish oil or long-chain n-3 polyunsaturated fatty acids. A random-effect model was used and between-studies heterogeneity was estimated with I(2). The quality of studies was assessed using Jadad and United States Preventive Services Task Force (USPSTF) scoring systems. All analyses were performed with RevMan (version 5.0.20).

RESULTS

Seven cohort studies and 11 randomized controlled trials (RCTs) were included in this meta-analysis. The pooled odds ratio (OR) was 0.79 (95% confidence interval [CI] = 0.56-1.12; p = 0.19) for RCTs and 0.83 (95% CI = 0.59-1.16; p = 0.27) for cohort studies. On sensitivity analysis, no statistically significant difference was noted when stratified by study design or quality of the studies (as graded by Jadad or USPSTF scoring systems).

CONCLUSION

This study does not suggest a major effect of fish/fish oil or n-3 fatty acids on the risk of AF.

Polyunsaturated Fatty acids in atrial fibrillation: looking for the proper candidates

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice with growing prevalence in developed countries. Several medical and interventional therapies, such as atrial specific drugs and pulmonary vein isolation, have demonstrated prevention of recurrences. However, their suboptimal long-term success and significant rate of secondary effects have led to intensive research in the last decade focused on novel alternative and supplemental therapies. One such candidate is polyunsaturated fatty acids (PUFAs). Because of their biological properties, safety, simplicity, and relatively cheap cost, there is a special clinical interest in omega-3 PUFAs as a possible antiarrhythmic agent. Obtained from diets rich in fish, they represent one of the current supplemental therapies. At the cellular level, an increasing body of evidence has shown that n-3 PUFAs exert a variety of effects on cardiac ion channels, membrane dynamic properties, inflammatory cascade, and other targets related to AF prevention. In this article, we review the current basic and clinical evidence pertinent to n-3 PUFAs in AF treatment and prevention. We also discuss controversial outcomes among clinical studies and propose specific subsets of AF patients who will benefit most from n-3 PUFAs.

Primary Prevention of Atrial Fibrillation where are we in 2012?

Drugs to alter or delay myocardial remodelling associated with heart failure, hypertension, or inflammation in the post-operative setting, may prevent the development of atrial fibrillation. Current experimental and clinical evidences support specific treatments for defined patient population (i.e. ACE-inhibitors and ARB for chronic heart failure and hypertension expecially with LV hypertrophy; statins, corticosteroids and possibly colchicine after cardiac surgery).

Fish, Marine n-3 Fatty Acids, and Atrial Fibrillation - Experimental Data and Clinical Effects

Marine n−3 polyunsaturated fatty acids (PUFA) may have beneficial effects in relation to atrial fibrillation (AF) with promising data from experimental animal studies, however, results from studies in humans have been inconsistent. This review evaluates the mechanisms of action of marine n−3 PUFA in relation to AF based on experimental data and provides a status on the evidence obtained from observational studies and interventional trials. In conclusion, there is growing evidence for an effect of marine n−3 PUFA in prevention and treatment of AF. However, further studies are needed to establish which patients are more likely to benefit from n−3 PUFA, the timing of treatment, and dosages.

Omega-3 fatty acids in the prevention of atrial fibrillation recurrences after cardioversion: a meta-analysis of randomized controlled trials

BACKGROUND

Previous randomized studies have reported conflicting results on the efficacy of omega-3 fatty acids in preventing atrial fibrillation (AF) recurrences after cardioversion.

OBJECTIVE

A systematic review and meta-analysis of the role of omega-3 fatty acids in the prevention of atrial fibrillation recurrences after cardioversion was conducted.

METHODS

PubMed, Cochrane Library, Elsevier, Science Online database were searched up to the end of January 2012 to identify all of the studies in human subjects that reported the effects of omega-3 fatty acids on the prevention of atrial fibrillation recurrences after cardioversion.

RESULTS

Overall, omega-3 fatty acids had no significant effect on the prevention of AF recurrences after cardioversion (OR: 0.63,95% CI 0.35-1.13; p=0.12). The heterogeneity among the studies was significant (p=0.01, I(2)=66%). Subgroup analysis showed that by administering omega-3 fatty acids at least 4 weeks prior to cardioversion and continuing thereafter, the recurrence rate of AF is significantly low (OR: 0.39, 95% CI 0.25-0.61; p<0.0001).

CONCLUSION

In the subgroup administered omega-3 fatty acids at least 4 weeks prior to cardioversion and continued thereafter, the recurrence rate of AF was significantly low. More double-blind, randomized, placebo-controlled, multicenter studies with high quality and longer follow-up periods are needed to affirm our conclusion.

Long-term omega-3 polyunsaturated fatty acid supplementation reduces the recurrence of persistent atrial fibrillation after electrical cardioversion

BACKGROUND

Persistent atrial fibrillation (AF) is associated with a high risk of recurrence after electrical cardioversion.

OBJECTIVE

We examined if long-term supplementation with omega-3 polyunsaturated fatty acids in fish oils commenced >1 month prior to electrical cardioversion and continued thereafter reduces recurrence of persistent AF.

METHODS

This was an open-label, randomized study of 178 patients with persistent AF >1-month duration. Participants were assigned to control group (n = 87) or omega-3 group (6 g/d fish oil; n = 91) and underwent cardioversion 1 month later. Concurrent antiarrhythmic use of sotalol or amiodarone was permitted. Fish oil was continued till return of persistent AF or a maximum of 1 year. Intention-to-treat analysis was performed for the primary end point defined as the recurrence of persistent AF.

RESULTS

Mean duration of fish oil intake was 56 days precardioversion and a total of 242 days in follow-up. Eicosapentaenoic acid and docosahexaenoic acid, the active components of fish oils, were 1.8-fold and 2.1-fold higher, respectively, in the omega-3 group compared with controls at the time of cardioversion (P <.001). At 90 days, 38.5% of the patients receiving omega-3 fatty acid supplement had AF recurrence compared with 77.5% of the controls (hazard ratio [omega-3 vs control] 0.38; 95% confidence interval 0.27-0.56; P <.001). Omega-3 intake was associated with a significant reduction in AF recurrence with or without concurrent antiarrhythmic drugs.

CONCLUSIONS

Omega-3 polyunsaturated fatty acid supplementation commenced >1 month prior to electrical cardioversion and continued thereafter reduces the recurrence of persistent AF. Randomized controlled trials on long-term fish oil supplementation are needed to confirm these findings.

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.