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

Tapping into Nature's Arsenal: Harnessing the Potential of Natural Antioxidants for Human Health and Disease Prevention

Numerous natural antioxidants commonly found in our daily diet have demonstrated significant benefits for human health and various diseases by counteracting the impact of reactive oxygen and nitrogen species. Their chemical properties enable a range of biological actions, including antihypertensive, antimicrobial, anti-inflammatory, anti-fibrotic, and anticancer effects. Despite promising outcomes from preclinical studies, ongoing debate persists regarding their reproducibility in human clinical models. This controversy largely stems from a lack of understanding of the pharmacokinetic properties of these compounds, coupled with the predominant focus on monotherapies in research, neglecting potential synergistic effects arising from combining different antioxidants. This study aims to provide an updated overview of natural antioxidants, operating under the hypothesis that a multitherapeutic approach surpasses monotherapy in efficacy. Additionally, this study underscores the importance of integrating these antioxidants into the daily diet, as they have the potential to prevent the onset and progression of various diseases. To reinforce this perspective, clinical findings pertaining to the treatment and prevention of non-alcoholic fatty liver disease and conditions associated with ischemia and reperfusion phenomena, including myocardial infarction, postoperative atrial fibrillation, and stroke, are presented as key references.

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.

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

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

Association Between Plasma Trans-Fatty Acid Concentrations and Measures of Glucose Homeostasis and Cardiovascular Risk Factors in Adults in NHANES 1999-2000

There is limited evidence on the association between plasma trans-fatty acids (TFAs) and cardiometabolic risk factors. Therefore, we examined the association between plasma TFA concentrations and glucose homeostasis and cardiovascular (CV) risk factors in adult Americans from the 1999 to 2000 National Health and Nutrition Examination Survey participants. Derivatized TFAs were separated by capillary gas chromatography. Of the 1678 participants, 46.5% were men. The mean age was 50.5 years overall, with no significant difference between men and women ( P = .101). In age-, sex- and race-adjusted analyses, mean waist circumference, fat-free mass, fat mass, C-peptide, insulin, hemoglobin A_1c (HbA_1c), homeostatic model assessment of insulin resistance (HOMA-IR), serum triglycerides (TGs), and total cholesterol (TC) increased across increasing quarters of TFAs (for all P < .001), while mean serum high-density lipoprotein cholesterol decreased across increasing quarters of plasma TFAs ( P < .001). In multivariable adjusted linear regressions, there remained significant positive associations between all plasma TFAs and body mass index, waist circumference, fat-free mass, fat mass, C-peptide, insulin, fasting blood glucose, HOMA-IR, HbA_1c, TGs, low-density lipoprotein cholesterol, and TC ( P < .001). In conclusion, our findings support a possible association between plasma TFAs concentrations and measures of glucose homeostasis and several CV risk factors.

Omega-3 polyunsaturated fatty acids reduce vascular tone and inflammation in human saphenous vein

Dietary intake of omega-3 polyunsaturated fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been reported to have beneficial cardiovascular effects. However, little is known about the effect of EPA and DHA on human vascular tone. Therefore, the aim of this study is to evaluate the effect of EPA and DHA on vascular tone of the human saphenous vein (SV) obtained from patients undergoing coronary bypass operation under normal and inflammatory conditions. Moreover, we aimed to investigate the effect of EPA and DHA on the release of inflammatory mediators from SV. Pretreatment of SV with EPA and DHA (100μM, 18h) decreased the contractile response of SV to norepinephrine (NE) under normal and inflammatory conditions. Moreover, EPA and DHA pretreatment diminished increased Monocyte Chemoattractant Protein-1 (MCP-1) and Tumor Necrosis Factor-alpha (TNF-α) release from SV under inflammatory conditions. In conclusion, our results suggest that EPA and DHA pretreatment may be beneficial to counteract graft vasospasm and vascular inflammation in SV which are important factors in graft failure development. Therefore, dietary intake of EPA and DHA may have potential clinical applications in improving coronary bypass graft patency.

Probing the intermolecular interactions of PPARγ-LBD with polyunsaturated fatty acids and their anti-inflammatory metabolites to infer most potential binding moieties

Background

PPARγ is an isoform of peroxisome proliferator-activated receptor (PPAR) belonging to a super family of nuclear receptors. PPARγ receptor is found to play a crucial role in the modulation of lipid and glucose homeostasis. Its commotion has been reported to play a significant role in a broad spectrum of diseases such as type 2 diabetes mellitus, inflammatory diseases, Alzheimer’s disease, and in some cancers. Hence, PPARγ is an important therapeutic target. Polyunsaturated fatty acids (PUFAs) and their metabolites (henceforth referred to as bioactive lipids) are known to function as agonists of PPARγ. However, agonistic binding modes and affinity of these ligands to PPARγ are yet to be deciphered.

Methods

In this study, we performed a comparative molecular docking, binding free energy calculation and molecular dynamics simulation to infer and rank bioactive lipids based on the binding affinities with the ligand binding domain (LBD) of PPARγ.

Results

The results inferred affinity in the order of resolvin E1 > neuroprotectin D1 > hydroxy-linoleic acid > docosahexaenoic acid > lipoxin A4 > gamma-linolenic acid, arachidonic acid > alpha-linolenic acid > eicosapentaenoic acid > linoleic acid. Of all the bioactive lipids studied, resolvin E1, neuroprotectin D1 and hydroxy-linoleic acid showed significant affinity comparable to proven PPARγ agonist namely, rosiglitazone, in terms of Glide XP docking score, H-bond formation with the key residues, binding free energy and stable complex formation with LBD favouring co-activator binding, as inferred through Molecular Dynamics trajectory analysis.

Conclusion

Hence, these three bioactive lipids (resolvin E1, neuroprotectin D1 and hydroxy-linoleic acid) may be favourably considered as ideal drug candidates in therapeutic modulation of clinical conditions such as type 2 DM, Alzheimer’s disease and other instances where PPARγ is a key player.

Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease.

Lipid-lowering and anti-inflammatory effects of omega 3 ethyl esters and krill oil: a randomized, cross-over, clinical trial

INTRODUCTION

Polyunsaturated fatty acids (PUFAs) derived from different sources could have different lipid-lowering effects in humans. The main aim of our study was to compare the short-term triglyceride-lowering efficacy of krill oil and purified omega 3 ethyl ester PUFAs in mildly overweight hypertriglyceridemic subjects.

MATERIAL AND METHODS

This double-blind, randomized clinical trial was carried out in 25 moderately hypertriglyceridemic subjects (TG = 150-500 mg/dl). After a 4-week run-in, participants were allocated to treatment with similar pills containing omega 3 ethyl ester PUFAs 1000 mg twice a day vs. krill oil 500 mg twice a day. After 4 weeks of treatment, participants were asked to observe a 4-week wash-out period, and they were then assigned to the alternative treatment for a further period of 4 weeks.

RESULTS

Although both PUFA sources were able to improve TG plasma levels, esterified omega 3 PUFAs were more efficacious than krill oil (p < 0.05). Nonetheless, only krill oil treatment was able to significantly improve high-density lipoprotein cholesterol and apolipoprotein AI levels, compared to both baseline (p < 0.05) and end of treatment with esterified omega 3 PUFAs (p < 0.05) values. Both treatments were able to significantly reduce high-sensitivity C-reactive protein (hs-CRP) levels from the baseline (p < 0.05), but krill oil improved it more efficaciously than esterified omega 3 PUFAs (p < 0.05).

CONCLUSIONS

Krill oil has lipid-lowering effects comparable with those obtained through a 4-fold higher dose of purified omega 3 ethyl ester PUFAs in mildly overweight hypertriglyceridemic subjects, while more efficaciously reducing hs-CRP.

Omega 3 and atrial fibrillation: Where are we?

Anti-arrhythmic properties of n-3 polyunsaturated fatty acids, at least in part mediated by anti-oxidant, anti-inflammatory and anti-fibrotic power, have been widely proved. Effect of fish oil on atrial fibrillation, both in primary and in secondary prevention and after cardiac surgery, are controversial, mostly due to lack of homogeneity between studies but also due to individual variability in response to fatty acids administration. Inclusion of measurement of incorporation of fish oil into cell membranes, appears to be essential in future studies, to assess their antiarrhythmic effect.

Potential role of dietary lipids in the prophylaxis of some clinical conditions

An imbalance of dietary lipids may potentially have a significant role in the pathobiology of some chronic diseases. Public health dietary fat recommendations have emphasized that low saturated fat, high monounsaturated fat, and high polyunsaturated fat with a lower ω-6 to ω-3 fatty acid ratio intake are necessary for normal health. However, such universal recommendations are likely to be hazardous, since the outcome of recommended lipid intake may depend on the consumption of other important dietary constituents that have an important role in the metabolism of lipids. In addition, consumption of fatty acids as per the individually tailored specific requirements in the context of other nutritional factors may have the potential to stabilize hormones, mood and sleep, and minimize adverse events. In support of this proposal, we review various factors that influence fatty acid metabolism, which need to be taken into consideration for appropriate utilization and consequently prevention of various diseases.

Bedside tool for predicting the risk of postoperative atrial fibrillation after cardiac surgery: the POAF score

Background

Atrial fibrillation (AF) remains the most common complication after cardiac surgery. The present study aim was to derive an effective bedside tool to predict postoperative AF and its related complications.

Methods and Results

Data of 17 262 patients undergoing adult cardiac surgery were retrieved at 3 European university hospitals. A risk score for postoperative AF (POAF score) was derived and validated. In the overall series, 4561 patients (26.4%) developed postoperative AF. In the derivation cohort age, chronic obstructive pulmonary disease, emergency operation, preoperative intra‐aortic balloon pump, left ventricular ejection fraction <30%, estimated glomerular filtration rate <15 mL/min per m² or dialysis, and any heart valve surgery were independent AF predictors. POAF score was calculated by summing weighting points for each independent AF predictor. According to the prediction model, the incidences of postoperative AF in the derivation cohort were 0, 11.1%; 1, 20.1%; 2, 28.7%; and ≥3, 40.9% (P<0.001), and in the validation cohort they were 0, 13.2%; 1, 19.5%; 2, 29.9%; and ≥3, 42.5% (P<0.001). Patients with a POAF score ≥3, compared with those without arrhythmia, revealed an increased risk of hospital mortality (5.5% versus 3.2%, P=0.001), death after the first postoperative day (5.1% versus 2.6%, P<0.001), cerebrovascular accident (7.8% versus 4.2%, P<0.001), acute kidney injury (15.1% versus 7.1%, P<0.001), renal replacement therapy (3.8% versus 1.4%, P<0.001), and length of hospital stay (mean 13.2 versus 10.2 days, P<0.001).

Conclusions

The POAF score is a simple, accurate bedside tool to predict postoperative AF and its related or accompanying complications.

A randomized controlled trial to prevent post-operative atrial fibrillation by antioxidant reinforcement

OBJECTIVES

This study was designed to assess whether the reinforcement of the antioxidant system, through n-3 fatty acids plus antioxidant vitamin supplementation, could reduce the incidence of post-operative atrial fibrillation.

BACKGROUND

Therapy to prevent post-operative atrial fibrillation remains suboptimal. Although oxidative stress plays a key role in the pathogenesis of this arrhythmia, antioxidant reinforcement has produced controversial results.

METHODS

A total of 203 patients scheduled for on-pump cardiac surgery were randomized to placebo or supplementation with n-3 polyunsaturated fatty acids (2 g/day) (eicosapentaenoic acid:docosahexaenoic acid ratio 1:2), vitamin C (1 g/day), and vitamin E (400 IU/day). The primary outcome was the occurrence of post-operative atrial fibrillation. Secondary outcomes were the biomarkers related to oxidative stress and inflammation.

RESULTS

Post-operative atrial fibrillation occurred in 10 of 103 patients (9.7%) in the supplemented group versus 32 of 100 patients (32%) in the placebo group (p < 0.001). Early after surgery, placebo patients presented with increased levels of biomarkers of inflammation and oxidative stress, which were markedly attenuated by antioxidant supplementation. The activity of catalase, superoxide dismutase, and glutathione peroxidase in atrial tissue of the supplemented patients was 24.0%, 17.1%, and 19.7% higher than the respective placebo values (p < 0.05). The atrial tissue of patients who developed atrial fibrillation showed NADPH oxidase p47-phox subunit protein and mRNA expression 38.4% and 35.7% higher, respectively, than patients in sinus rhythm (p < 0.05).

CONCLUSIONS

This safe, well-tolerated, and low-cost regimen, consisting of n-3 polyunsaturated fatty acids plus vitamins C and E supplementation, favorably affected post-operative atrial fibrillation, increased antioxidant potential, and attenuated oxidative stress and inflammation. (Prevention of Post-Operative Atrial Fibrillation: Pathophysiological Characterization of a Pharmacological Intervention Based on a Novel Model of Nonhypoxic Pre-Conditioning; ISRCTN45347268).

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.

APOE genotype modifies the association between plasma omega-3 fatty acids and plasma lipids in the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

The benefits of fish oil fatty acids eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) on plasma lipid profiles have been inconsistent but may partially depend on individual Apolipoprotein E (APOE) genotypes. We aimed to determine whether APOE genotype modifies the association of lipid profile characteristics with plasma EPA and DHA levels.

METHODS

APOE genotype was determined in this cross-sectional analysis of 2340 Multi-Ethnic Study of Atherosclerosis (MESA) participants. Relative plasma phospholipid EPA and DHA levels, plasma lipids, and lipoprotein subclass particle sizes and concentrations were measured.

RESULTS

Significant gene-EPA interactions were found with HDL-C, and particle concentrations of large and total HDL (p(interaction) = 0.0002, 0.006, and 0.007, respectively). The above lipid targets were positively associated with EPA in the E2 groups, whereas negative trends were observed among the E4 participants. Gene-DHA interactions were noted for small LDL particle concentrations alone (p(interaction) = 0.01), where a positive trend was found among E4 but not E2 or E3 participants.

CONCLUSIONS

These results indicate a significant contribution of the APOE genotype to the EPA-lipid profile relationship; however, the results do not explain the differences in previous findings regarding LDL-C, triglycerides or total cholesterol. Future investigators examining the effects of EPA on HDL-C or lipoprotein characteristics may consider including APOE genotype in their analyses.

Atrial fibrillation in the 21st century: a current understanding of risk factors and primary prevention strategies

Atrial fibrillation (AF) is the most common arrhythmia worldwide, and it has a significant effect on morbidity and mortality. It is a significant risk factor for stroke and peripheral embolization, and it has an effect on cardiac function. Despite widespread interest and extensive research on this topic, our understanding of the etiology and pathogenesis of this disease process is still incomplete. As a result, there are no set primary preventive strategies in place apart from general cardiology risk factor prevention goals. It seems intuitive that a better understanding of the risk factors for AF would better prepare medical professionals to initially prevent or subsequently treat these patients. In this article, we discuss widely established risk factors for AF and explore newer risk factors currently being investigated that may have implications in the primary prevention of AF. For this review, we conducted a search of PubMed and used the following search terms (or a combination of terms): atrial fibrillation, metabolic syndrome, obesity, dyslipidemia, hypertension, type 2 diabetes mellitus, omega-3 fatty acids, vitamin D, exercise toxicity, alcohol abuse, and treatment. We also used additional articles that were identified from the bibliographies of the retrieved articles to examine the published evidence for the risk factors of AF.

Omega-3 Polyunsaturated Fatty Acid Supplementation: Mechanism and Current Evidence in Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent arrhythmia and is associated with considerable morbidity and mortality. Available pharmacologic antiarrhythmic therapies are often ineffective in preventing the recurrence of AF, possibly because these drugs target a single pathophysiological mechanism. Given their beneficial effects on ventricular arrhythmias, omega-3 polyunsaturated fatty acids (n-3 PUFAs) have recently been investigated as possible candidates in the treatment of supraventricular arrhythmias. In this review, we explore the current understanding of the antiarrhythmic effects attributed to n-3 PUFAs including direct modulation of ionic channels, improvement of membrane fluidity, anti-inflammatory and antifibrotic effects, and modulation of sympatho-vagal balance. We will then focus on the results of epidemiologic studies exploring the associations between nutritional intake of n3 PUFAs and the incidence of AF, and will review the findings of the clinical trials investigating the effects of n-3 PUFAs supplementation in the prophylaxis of AF and in the prevention of its recurrences.

How Are n-3 LCPUFAs Antiarrhythmic? A Reassessment of n-3 LCPUFAs in Cardiac Disease

Long-chain n-3-polyunsaturated fatty acids (n-3 LCPUFAs), referring particularly to marine-derived eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to be effective in treating arrhythmias in some clinical trials and animal studies. The mechanism for this effect of n-3 LCPUFAs is not well understood. Experimental studies and clinical trials published in the 1980s and 1990s suggested that n-3 LCPUFAs may be antiarrhythmic drugs, but more recent trials have not confirmed this. In this paper, we examine evidence for, and against, the direct antiarrhythmic action of n-3 LCPUFAs and suggest that antistructural remodeling effects of n-3 LCPUFAs may be more relevant in accounting for their clinical effects.

Ageing improves the antioxidant response against postoperative atrial fibrillation: a randomized controlled trial

OBJECTIVES

Extracorporeal circulation is associated with ischaemia-reperfusion-induced oxidative stress and atrial fibrillation (AF). Ageing is the major risk factor for this arrhythmia. Reinforcing the antioxidant defence system would be expected to protect the myocardium against ischaemia-reperfusion damage. We studied the effect of antioxidant reinforcement and ageing on the occurrence of postoperative AF.

METHODS

A randomized, double-blind, placebo-controlled trial was performed in patients scheduled for cardiac surgery with extracorporeal circulation. Supplementation with omega-3 polyunsaturated fatty acid (PUFA) and vitamins C and E, or placebo was administered to 152 patients divided by age: young patients (30-59 years) and old patients (60-80 years). For the detection of AF, we used 12-lead and Holter EKGs. Antioxidant enzyme activity was determined in atrial tissue. Oxidative stress was assessed through plasma malondialdehyde levels.

RESULTS

Supplemented patients over 60 years old showed higher glutathione peroxidase activity than control patients in the same age range. There was no difference between the supplemented and placebo groups in patients under 60 years old. The decrease in the incidence of postoperative AF in supplemented patients was more marked in the older patients than in the younger ones.

CONCLUSIONS

Since the antioxidant supplementation with n-3 PUFAs and vitamins C and E resulted in a more marked reduction of postoperative AF in older patients, it could be suggested that the efficacy of this therapy improves with ageing.

Effects of n-3 Polyunsaturated Fatty Acids on Cardiac Ion Channels

Dietary n−3 polyunsaturated fatty acids (PUFAs) have been reported to exhibit antiarrhythmic properties, and these effects have been attributed to their capability to modulate ion channels. In the present review, we will focus on the effects of PUFAs on a cardiac sodium channel (Na_v1.5) and two potassium channels involved in cardiac atrial and ventricular repolarization (K_v) (K_v1.5 and K_v11.1). n−3 PUFAs of marine (docosahexaenoic, DHA and eicosapentaenoic acid, EPA) and plant origin (alpha-linolenic acid, ALA) block K_v1.5 and K_v11.1 channels at physiological concentrations. Moreover, DHA and EPA decrease the expression levels of K_v1.5, whereas ALA does not. DHA and EPA also decrease the magnitude of the currents elicited by the activation of Na_v1.5 and calcium channels. These effects on sodium and calcium channels should theoretically shorten the cardiac action potential duration (APD), whereas the blocking actions of n−3 PUFAs on K_v channels would be expected to produce a lengthening of cardiac action potential. Indeed, the effects of n−3 PUFAs on the cardiac APD and, therefore, on cardiac arrhythmias vary depending on the method of application, the animal model, and the underlying cardiac pathology.

A Randomized, Placebo-Controlled Trial of Omega-3 Fatty Acids for Inhibition of Supraventricular Arrhythmias After Cardiac Surgery: The FISH Trial

BACKGROUND

Omega-3 polyunsaturated fatty acids (n3-PUFAs) might have antiarrhythmic properties, but data conflict on whether n3-PUFAs reduce rates of atrial fibrillation (AF) after coronary artery bypass graft surgery (CABG). We hypothesized that n3-PUFAs would reduce post-CABG AF, and we tested this hypothesis in a well-powered, randomized, double-blind, placebo-controlled, multicenter clinical trial.

METHODS AND RESULTS

Patients undergoing CABG were randomized to pharmaceutical-grade n3-PUFAs 2 g orally twice daily (minimum of 6 g) or a matched placebo ≥24 hours before surgery. Gas chromatography was used to assess plasma fatty acid composition of samples collected on the day of screening, day of surgery, and postoperative day 4. Treatment continued either until the primary end point, clinically significant AF requiring treatment, occurred or for a maximum of 2 weeks after surgery. Two hundred sixty patients were enrolled and randomized. Before surgery, n3-PUFA dosing increased plasma n3-PUFA levels from 2.9% to 4% and reduced the n6:n3-PUFA ratio from 9.1 to 6.4 (both P<0.001). Similar changes were noted on postoperative day 4. There were no lipid changes in the placebo group. The rate of post-CABG AF was similar in both groups (30% n3-PUFAs versus 33% placebo, P=0.67). The post-CABG AF odds ratio for n3-PUFAs relative to placebo was 0.89 (95% confidence interval 0.52-1.53). There were no differences in any secondary end points.

CONCLUSIONS

Oral n3-PUFA supplementation begun 2 days before CABG did not reduce AF or other complications after surgery.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov Unique identifier: NCT00446966. (J Am Heart Assoc. 2012;1:e000547 doi: 10.1161/JAHA.111.000547.).

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.

Fish, fish-derived n-3 fatty acids, and risk of incident atrial fibrillation in the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Results of observational and experimental studies investigating the association between intake of long-chain n-3 polyunsaturated fatty acids (PUFAs) and risk of atrial fibrillation (AF) have been inconsistent.

METHODS

We studied the association of fish and the fish-derived n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with the risk of incident AF in individuals aged 45-64 from the Atherosclerosis Risk in Communities (ARIC) cohort (n = 14,222, 27% African Americans). Intake of fish and of DHA and EPA were measured via food frequency questionnaire. Plasma levels of DHA and EPA were measured in phospholipids in a subset of participants (n = 3,757). Incident AF was identified through the end of 2008 using ECGs, hospital discharge codes and death certificates. Cox proportional hazards regression was used to estimate hazard ratios of AF by quartiles of n-3 PUFAs or by fish intake.

RESULTS

During the average follow-up of 17.6 years, 1,604 AF events were identified. In multivariable analyses, total fish intake and dietary DHA and EPA were not associated with AF risk. Higher intake of oily fish and canned tuna was associated with a nonsignificant lower risk of AF (p for trend = 0.09). Phospholipid levels of DHA+EPA were not related to incident AF. However, DHA and EPA showed differential associations with AF risk when analyzed separately, with lower risk of AF in those with higher levels of DHA but no association between EPA levels and AF risk.

CONCLUSIONS

In this racially diverse sample, dietary intake of fish and fish-derived n-3 fatty acids, as well as plasma biomarkers of fish intake, were not associated with AF risk.

Omega-3 Fatty acids: anti-arrhythmic, pro-arrhythmic, or both?

This review focuses on developments after 2008, when the topic was last reviewed by the author. Pertinent publications were found by medline searches and in the author’s personal data base. Prevention of atrial fibrillation (AF) was investigated in a number of trials, sparked by one positive report on the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), considerations of upstream therapy, data from electrophysiologic laboratories and animal experiments. If EPA + DHA prevent postoperative AF, the effect is probably smaller than initially expected. The same is probably true for maintenance of sinus rhythm after cardioversion and for new-onset AF. Larger trials are currently ongoing. Prevention of ventricular arrhythmias was studied in carriers of an implanted cardioverter-defibrillator, with no clear results. This might have been due to a broad definition of the primary endpoint, including any ventricular arrhythmia and any action of the device. Epidemiologic studies support the contention that high levels of EPA + DHA prevent sudden cardiac death (SCD). However, since SCD is a rare occurrence, it is difficult to conduct an adequately powered trial. In patients with congestive heart failure, EPA + DHA reduced total mortality and rehospitalizations, but not SCD or presumed arrhythmic death. Of three trials in patients after a myocardial infarction, two were inadequately powered, and in one, the dose might have been too low. Taken together, while epidemiologic studies support an inverse relation between EPA + DHA and occurrence of SCD or arrhythmic death, demonstrating this effect in intervention trials remained elusive so far. A pro-arrhythmic effect of EPA + DHA has not been seen in intervention studies, and results of epidemiologic and animal studies also rather argue against such an effect. A different, and probably more productive, perspective is provided by a standardized analytical assessment of a person’s status in EPA + DHA by use of the omega-3 index, EPA + DHA in red cell fatty acids. In populations with a high omega-3 index, SCD is rare. Intervention trials can become more effective by including a low omega-3 index into the inclusion criteria, thus creating a study population more likely to demonstrate an effect of EPA + DHA. This is especially relevant in case of rare endpoints, like new-onset AF or SCD.

Prevention of postoperative atrial fibrillation: novel and safe strategy based on the modulation of the antioxidant system

Postoperative atrial fibrillation (AF) is the most common arrhythmia following cardiac surgery with extracorporeal circulation. The pathogenesis of postoperative AF is multifactorial. Oxidative stress, caused by the unavoidable ischemia-reperfusion event occurring in this setting, is a major contributory factor. Reactive oxygen species (ROS)-derived effects could result in lipid peroxidation, protein carbonylation, or DNA oxidation of cardiac tissue, thus leading to functional and structural myocardial remodeling. The vulnerability of myocardial tissue to the oxidative challenge is also dependent on the activity of the antioxidant system. High ROS levels, overwhelming this system, should result in deleterious cellular effects, such as the induction of necrosis, apoptosis, or autophagy. Nevertheless, tissue exposure to low to moderate ROS levels could trigger a survival response with a trend to reinforce the antioxidant defense system. Administration of n-3 polyunsaturated fatty acids (PUFA), known to involve a moderate ROS production, is consistent with a diminished vulnerability to the development of postoperative AF. Accordingly, supplementation of n-3 PUFA successfully reduced the incidence of postoperative AF after coronary bypass grafting. This response is due to an up-regulation of antioxidant enzymes, as shown in experimental models. In turn, non-enzymatic antioxidant reinforcement through vitamin C administration prior to cardiac surgery has also reduced the postoperative AF incidence. Therefore, it should be expected that a mixed therapy result in an improvement of the cardioprotective effect by modulating both components of the antioxidant system. We present novel available evidence supporting the hypothesis of an effective prevention of postoperative AF including a two-step therapeutic strategy: n-3 PUFA followed by vitamin C supplementation to patients scheduled for cardiac surgery with extracorporeal circulation. The present study should encourage the design of clinical trials aimed to test the efficacy of this strategy to offer new therapeutic opportunities to patients challenged by ischemia-reperfusion events not solely in heart, but also in other organs such as kidney or liver in transplantation surgeries.

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.

Fish Oil

Fish and fish oil supplements are often used to lower triglycerides; however, recent studies suggest the beneficial use of fish oil for other cardiovascular reasons. Studies have shown that in addition to decreasing triglycerides, fish oil has shown benefit in providing antiplatelet activity, improving heart failure, and improving vascular function in diabetes. Fish oil was shown to improve triglycerides in combination with other lipid-lowering therapy such as a statin or fibrate. Fish oil also had effects on lowering total cholesterol, very-low-density lipoprotein (VLDL), and increasing high-density lipoprotein (HDL). In terms of its antiplatelet activity, fish oil was shown to lower platelet aggregation when given in combination with clopidogrel and aspirin therapy during PCI, thus fish oil appears to enhance platelet response to clopidogrel. Fish oil has a role in heart failure as well. Fish oil was shown to slightly decrease morbidity and mortality in patients with class II-IV heart failure compared to placebo. Finally, fish oil showed benefit in patients with type II diabetes in terms of improving micro- and macrovascular function.

Do omega-3 fatty acids prevent atrial fibrillation after open heart surgery? A meta-analysis of randomized controlled trials

OBJECTIVES

N-3 polyunsaturated fatty acids have been proposed as a novel treatment for preventing postoperative atrial fibrillation due to their potential anti-inflammatory and anti-arrhythmic effects. However, randomized studies have yielded conflicting results. The objective of this study is to review randomized trials of N-3 polyunsaturated fatty acid use for postoperative atrial fibrillation.

METHODS

Using the CENTRAL, PUBMED, EMBASE, and LILACS databases, a literature search was conducted to identify all of the studies in human subjects that reported the effects of N-3 polyunsaturated fatty acids on the prevention of postoperative atrial fibrillation in cardiac surgery patients. The final search was performed on January 30, 2011. There was no language restriction, and the search strategy only involved terms for N-3 polyunsaturated fatty acids (or fish oil), atrial fibrillation, and cardiac surgery. To be included, the studies had to be randomized (open or blinded), and the enrolled patients had to be ≥18 years of age.

RESULTS

Four randomized studies (three double-blind, one open-label) that enrolled 538 patients were identified. The patients were predominantly male, the mean age was 62.3 years, and most of the patients exhibited a normal left atrial size and ejection fraction. N-3 polyunsaturated fatty acid use was not associated with a reduction in postoperative atrial fibrillation. Similar results were observed when the open-label study was excluded.

CONCLUSIONS

There is insufficient evidence to suggest that treatment with N-3 polyunsaturated fatty acids reduces postoperative atrial fibrillation. Therefore, their routine use in patients undergoing cardiac surgery is not recommended.