Dietary fish oil protects against stretch-induced vulnerability to atrial fibrillation in a rabbit model

The Cardioprotective Effects of Polyunsaturated Fatty Acids Depends on the Balance Between Their Anti- and Pro-Oxidative Properties

Polyunsaturated fatty acids (PUFAs) are not only structural components of membrane phospholipids and energy storage molecules in cells. PUFAs are important factors that regulate various biological functions, including inflammation, oxidation, and immunity. Both n-3 and n-6 PUFAs from cell membranes can be metabolized into pro-inflammatory and anti-inflammatory metabolites that, in turn, influence cardiovascular health in humans. The role that PUFAs play in organisms depends primarily on their structure, quantity, and the availability of enzymes responsible for their metabolism. n-3 PUFAs, such as eicosapentaenoic (EPA) and docosahexaenoic (DHA), are generally known for anti-inflammatory and atheroprotective properties. On the other hand, n-6 FAs, such as arachidonic acid (AA), are precursors of lipid mediators that display mostly pro-inflammatory properties and may attenuate the efficacy of n-3 by competition for the same enzymes. However, a completely different light on the role of PUFAs was shed due to studies on the influence of PUFAs on new-onset atrial fibrillation. This review analyzes the role of PUFAs and PUFA derivatives in health-related effects, considering both confirmed benefits and newly arising controversies.

n-3 fatty acids and the risk of atrial fibrillation, review

Atrial fibrillation (AF) is the most frequent type of cardiac arrhythmia that affects over six million individuals in Europe. The incidence and prevalence of AF rises with age, and often occurs after cardiac surgery. Other risk factors correlated with AF comprise high blood pressure, diabetes mellitus, left atrial enlargement, ischemic heart disease, and congestive heart failure. Considering the high prevalence of AF in aging societies, strategies to prevent serious complications, such as stroke or heart failure, are important because they are correlated with high morbidity and mortality. The supplementation of sea-derived n-3 polyunsaturated fatty acids (PUFA) is widely discussed in this context, but the results of experimental and observational studies are in contrast to randomized placebo-controlled intervention trials (RCTs). Specifically, larger placebo-controlled n-3 PUFA supplementation studies with long follow-up showed a dose-dependent rise in incident AF. Daily n-3 PUFA doses of ≥1 g/d are correlated with a 50 % increase in AF risk, whereas a daily intake of <1 g/d causes AF in only 12 %. Individuals with a high cardiovascular risk (CVD) risk and high plasma-triglycerides seem particularly prone to develop AF upon n-3 PUFA supplementation. Therefore, we should exercise caution with n-3 PUFA supplementation especially in patients with higher age, CVD, hypertriglyceridemia or diabetes. In summary, existing data argue against the additive intake of n-3 PUFA for preventative purposes because of an incremental AF risk and lacking CVD benefits. However, more clinical studies are required to disentangle the discrepancy between n-3 PUFA RCTs and observational studies showing a lower CVD risk in individuals who regularly consume n-3 PUFA-rich fish.

Omega-3 Fatty Acids and Arrhythmias

The pro- and antiarrhythmic effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been extensively studied in preclinical and human trials. Despite early evidence of an antiarrhythmic role of n-3 PUFA in the prevention of sudden cardiac death and postoperative and persistent atrial fibrillation (AF), subsequent well-designed randomized trials have largely not shown an antiarrhythmic benefit. Two trials that tested moderate and high-dose n-3 PUFA demonstrated a reduction in sudden cardiac death, but these findings have not been widely replicated, and the potential of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to reduce arrhythmic death in combination, or as monotherapy, remains uncertain. The accumulated clinical evidence does not support supplementation of n-3 PUFA for postoperative AF or secondary prevention of AF. Several large, contemporary, randomized controlled trials of high-dose n-3 PUFA for primary or secondary cardiovascular prevention have demonstrated a small, significant, dose-dependent increased risk of incident AF compared with mineral oil or corn oil comparator. These findings were reproduced with both icosapent ethyl monotherapy and a mixed EPA+DHA formulation. The proarrhythmic mechanism of increased AF in contemporary cohorts exposed to high-dose n-3 PUFA is unknown. EPA and DHA and their metabolites have pleiotropic cardiometabolic and pro- and antiarrhythmic effects, including modification of the lipid raft microenvironment; alteration of cell membrane structure and fluidity; modulation of sodium, potassium, and calcium currents; and regulation of gene transcription, cell proliferation, and inflammation. Further characterization of the complex association between EPA, EPA+DHA, and DHA and AF is needed. Which formulations, dose ranges, and patient subgroups are at highest risk, remain unclear.

Efficacy and Safety of Omega-3 Fatty Acids in the Prevention of Cardiovascular Disease: A Systematic Review and Meta-analysis

BACKGROUND

It is widely accepted that omega-3 fatty acids are beneficial in the prevention of cardiovascular disease, but many large randomized controlled trial studies and meta-analyses have come to different conclusions. The evidence for omega-3 fatty acids supplementation to prevent cardiovascular disease remains insufficient. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of several types of omega-3 fatty acids supplements.

METHODS

We comprehensively searched the online database and found 15 RCTs. The primary efficacy outcomes included major cardiovascular events, myocardial infarction, heart failure, atrial fibrillation, stroke, cardiovascular death, and all-cause death. The safety endpoints included gastrointestinal problems, bleeding-related disorders, and cancer. Subgroup analysis was conducted according to the main characteristics of the population, and the dose-response relationship of omega-3 fatty acids was evaluated by meta-regression. All results were calculated by the random effect model. Statistical heterogeneity was assessed using chi-square tests and quantified using I-square statistics.

RESULTS

The incidence of major cardiovascular events (RR 0.95, 95%CI 0.91 to 0.99, P = 0.026), myocardial infarction (RR 0.90, 95%CI 0.83 to 0.98; P = 0.021), and cardiovascular death (RR 0.94, 95%CI 0.88 to 0.99; P = 0.028) was reduced in the omega-3 fatty acid group compared with the control group. An increased risk of atrial fibrillation (RR 1.25, 95%CI 1.10 to 1.41; P = 0.000) was observed in patients in the omega-3 fatty acid group. No statistical differences were observed between the two groups in heart failure, stroke, and all-cause death. For safety endpoints, there were no statistically significant differences between the two groups in gastrointestinal problems, bleeding-related disorders, and cancer. Subgroup analysis showed that the cardiovascular benefit of omega-3 fatty acids was primarily attributable to the prescription of EPA ethyl ester. Omega-3 fatty acids may reduce the risk of major cardiovascular events in patients with cardiovascular disease or risk factors, and reduce the risk of myocardial infarction in patients without cardiovascular disease; however, they may increase the risk of stroke in patients with myocardial infarction. In addition, prescription omega-3 acid ethyl ester has a good safety profile, and prescription EPA ethyl ester has a high risk of bleeding.

CONCLUSION

Moderate evidence showed that the use of omega-3 fatty acids may reduce the risk of major cardiovascular events, myocardial infarction, and cardiovascular death. Compared to other types of omega-3 fatty acids supplements, we support the use of prescription EPA ethyl ester formulations for the prevention of cardiovascular disease, but the potential risk of atrial fibrillation and bleeding cannot be ignored. It is important to note that omega-3 fatty acids should be applied with caution in patients with previous myocardial infarction, which may increase the risk of stroke. Finally, omega-3 fatty acids are relatively safe and in general do not increase gastrointestinal problems, bleeding-related disorders, or cancer, but attention needs to be paid to the risk of bleeding with prescription EPA ethyl ester formulations.

In Vitro Models for Improved Therapeutic Interventions in Atrial Fibrillation

Atrial fibrillation is the most common type of cardiac arrhythmias in humans, mostly caused by hyper excitation of specific areas in the atrium resulting in dyssynchronous atrial contractions, leading to severe consequences such as heart failure and stroke. Current therapeutics aim to target this condition through both pharmacological and non-pharmacological approaches. To test and validate any of these treatments, an appropriate preclinical model must be carefully chosen to refine and optimise the therapy features to correctly reverse this condition. A broad range of preclinical models have been developed over the years, with specific features and advantages to closely mimic the pathophysiology of atrial fibrillation. In this review, currently available models are described, from traditional animal models and in vitro cell cultures to state-of-the-art organoids and organs-on-a-chip. The advantages, applications and limitations of each model are discussed, providing the information to select the appropriate model for each research application.

Omega-3 fatty acids and atrial fibrillation

Although some clinical trials have demonstrated reduced incidence of cardiovascular disease with the use of omega-3 fatty acids, others have found an increased risk of atrial fibrillation (AF). AF is the most common sustained cardiac arrhythmia worldwide. It is associated with high morbidity and mortality rates and significant public health burden. Previous studies of the effect of omega-3 fatty acids on AF occurrence have reported contradictory results. Here we reviewed the effect of omega-3 fatty acids on the risk of AF.

Mediterranean Diet: A Tool to Break the Relationship of Atrial Fibrillation with the Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease

Atrial fibrillation (AF) is the most common supraventricular arrhythmia associated with increased cardiovascular and non-cardiovascular morbidity and mortality. As multiple factors may predispose the onset of AF, the prevention of the occurrence, recurrence and complications of this arrhythmia is still challenging. In particular, a high prevalence of cardio-metabolic comorbidities such as the metabolic syndrome (MetS) and in its hepatic manifestation, the non-alcoholic fatty liver disease (NAFLD), have been described in the AF population. A common pathogenetic mechanism linking AF, MetS and NAFLD is represented by oxidative stress. For this reason, in the past decades, numerous studies have investigated the effect of different foods/nutrients with antioxidant properties for the prevention of, and their therapeutic role is still unclear. In this narrative comprehensive review, we will summarize current evidence on (1) the association between AF, MetS and NAFLD (2) the antioxidant role of Mediterranean Diet and its components for the prevention of AF and (3) the effects of Mediterranean Diet on MetS components and NAFLD.

Association Between Omega-3 Fatty Acid Treatment and Atrial Fibrillation in Cardiovascular Outcome Trials: A Systematic Review and Meta-Analysis

PURPOSE

Data on the relationship between omega-3 fatty acid (n-3 FA) therapy with atrial fibrillation (AF) have been inconsistent. We investigate the association between n-3 FA and risk for AF by pooling data from available large, cardiovascular outcome trials.

METHODS

We performed a systematic search on PubMed and Embase for studies on n-3 FA with AF as an outcome measure. Large (≥ 1000 participants) randomized controlled trials with ≥ 1-year follow-up period were included. The association between n-3 FA and risk of AF or stroke was assessed. Mantel-Haenszel random effects model was used to calculate risk ratios (RR) with 95% confidence intervals (CI). We then performed meta-regression to evaluate effect on AF by dose of n-3 FA therapy.

RESULTS

A total of 8 randomized control trials encompassing 83,112 participants were included in the meta-analysis. Of these, five trials assessed a lower dose of n-3 FA (≤ 1 g daily, n = 61,096) while 3 trials assessed a higher dose (> 1 g daily, n = 22,016). In meta-analysis, a significant association was noted between n-3 FA treatment and risk of AF (4.0% vs 3.3%; RR 1.24, 95% CI 1.11-1.38, p = 0.0002). There was a modest but still significant association in the lower dose (n-3 FA ≤ 1 g daily) sub-group (RR 1.12, 95% CI 1.04-1.21, p = 0.004) and stronger association in the higher dose (n-3 FA > 1 g daily) sub-group (RR 1.51, 95% CI 1.26-1.80, p < 0.001; p-interaction between low versus high subgroups = 0.003). There was no increase in stroke risk (RR 1.04, 95% CI 0.90-1.20). Meta-regression demonstrated a significant association between dose of n-3 FA with risk for AF events (log RR 0.103, 95% CI 0.048-0.159, p < 0.001).

CONCLUSION

While overall AF event rates were low, n-3 FA treatment is associated with increased risk for AF.

Novel high-docosahexaenoic-acid tuna oil supplementation modulates gut microbiota and alleviates obesity in high-fat diet mice

Studies have documented the benefits of fish oil in different diseases because of its high n-3 polyunsaturated fatty acid content. However, these studies mostly used commercially available fish oil supplements with a ratio of 18/12 for eicosapentaenoic acid and docosahexaenoic acid (DHA). However, increasing DHA content for this commonly used ratio might bring out a varied metabolic effect, which have remained unclear. Thus, in this study, a novel tuna oil (TO) was applied to investigate the effect of high-DHA content on the alteration of the gut microbiota and obesity in high-fat diet mice. The results suggest that high-DHA TO (HDTO) supplementation notably ameliorates obesity and related lipid parameters and restores the expression of lipid metabolism-related genes. The benefits of TOs were derived from their modification of the gut microbiota composition and structure in mice. A high-fat diet triggered an increased Firmicutes/Bacteroidetes ratio that was remarkably restored by TOs. The number of obesity-promoting bacteria-Desulfovibrio, Paraeggerthella, Terrisporobacter, Millionella, Lachnoclostridium, Anaerobacterium, and Ruminiclostridium-was dramatically reduced. Desulfovibrio desulfuricans, Alistipes putredinis, and Millionella massiliensis, three dysbiosis-related species, were especially regulated by HDTO. Regarding the prevention of obesity, HDTO outperforms the normal TO. Intriguingly, HDTO feeding to HFD-fed mice might alter the arginine and proline metabolism of intestinal microbiota.

Cardiac Mechano-Electric Coupling: Acute Effects of Mechanical Stimulation on Heart Rate and Rhythm

The heart is vital for biological function in almost all chordates, including humans. It beats continually throughout our life, supplying the body with oxygen and nutrients while removing waste products. If it stops, so does life. The heartbeat involves precise coordination of the activity of billions of individual cells, as well as their swift and well-coordinated adaption to changes in physiological demand. Much of the vital control of cardiac function occurs at the level of individual cardiac muscle cells, including acute beat-by-beat feedback from the local mechanical environment to electrical activity (as opposed to longer term changes in gene expression and functional or structural remodeling). This process is known as mechano-electric coupling (MEC). In the current review, we present evidence for, and implications of, MEC in health and disease in human; summarize our understanding of MEC effects gained from whole animal, organ, tissue, and cell studies; identify potential molecular mediators of MEC responses; and demonstrate the power of computational modeling in developing a more comprehensive understanding of ‟what makes the heart tick.ˮ.

How does high DHA fish oil affect health? A systematic review of evidence

The health benefits of fish oil, and its omega-3 long chain polyunsaturated fatty acid content, have attracted much scientific attention in the last four decades. Fish oils that contain higher amounts of eicosapentaenoic acid (EPA; 20:5n-3) than docosahexaenoic acid (DHA; 22:6n-3), in a distinctive ratio of 18/12, are typically the most abundantly available and are commonly studied. Although the two fatty acids have traditionally been considered together, as though they were one entity, different physiological effects of EPA and DHA have recently been reported. New oils containing a higher quantity of DHA compared with EPA, such as fractionated and concentrated fish oil, tuna oil, calamari oil and microalgae oil, are increasingly becoming available on the market, and other oils, including those extracted from genetically modified oilseed crops, soon to come. This systematic review focuses on the effects of high DHA fish oils on various human health conditions, such as the heart and cardiovascular system, the brain and visual function, inflammation and immune function and growth/Body Mass Index. Although inconclusive results were reported in several instances, and inconsistent outcomes observed in others, current data provides substantiated evidence in support of DHA being a beneficial bioactive compound for heart, cardiovascular and brain function, with different, and at times complementary, effects compared with EPA. DHA has also been reported to be effective in slowing the rate of cognitive decline, while its possible effects on depression disorders are still unclear. Interestingly, gender- and age- specific divergent roles for DHA have also been reported. This review provides a comprehensive collection of evidence and a critical summary of the documented physiological effects of high DHA fish oils for human health.

Atrial fibrillation and its complications in arterial hypertension: The potential preventive role of ω-3 polyunsaturated fatty acids

Atrial fibrillation (AF) is the most common type of arrhythmia in the general population with a prevalence that reaches one third of patients with arterial hypertension. Several risk factors frequently associated with hypertension predispose the myocardium to AF by inducing atrial inflammation and fibrosis and altering atrial electrical and mechanical characteristics. AF influences the quality of life of hypertensive patients since it increases incidence of stroke and other thromboembolic events, and mortality. Polyunsaturated fatty acids of the ω-3 family (ω-3 PUFA) have been demonstrated to be beneficial in cardiovascular disease prevention by reducing plasma lipids and blood pressure levels and decreasing the risk of sudden death. These fatty acids can act as potent anti-inflammatory and anti-arrhythmic agents. Many studies have investigated a possible preventive effect of ω-3 PUFA on incident AF reporting contradictory results. This article overviews the evidence currently available on this important topic and provides some conclusive remarks on the possibility that these fatty acids could be beneficial in hypertensive patients.

A meta-analysis on Omega-3 supplements in preventing recurrence of atrial fibrillation

Previous studies had suggested that Omega-3 fatty acids have pleiotropic effects and favourable safety profile, which may potentially increase the efficacy of antiarrhythmic drugs in suppressing atrial arrhythmias through combination therapy. This meta-analysis aimed to determine the effectiveness of using Omega-3 polyunsaturated fatty acids as a sole anti-arrhythmic agent or as an adjunct to existing pharmacological therapies in preventing atrial fibrillation recurrence. Randomized controlled trials published in English, from inception to December 2016, were considered. We searched for published studies in the following electronic databases: Cochrane Central Register of Controlled Trials, PubMed, EMBASE, Medline, Scopus, and Cumulative Index to Nursing and Allied Health Literature. Pooled hazard ratio (HR) and corresponding 95% confidence intervals (CI) for time to first atrial fibrillation recurrence was analysed using a fixed effects model. Four RCTs with 1,268 participants were included in the review. Our results showed that Omega-3 polyunsaturated fatty acid therapy had no effect on preventing atrial fibrillation recurrence compared to control/placebo group (HR: 1.13, 95% CI: 0.96 to 1.33, p = 0.14), with no significant heterogeneity found among those studies (Q value = 0.15, 9 = 0.99, I² = 0%). Therefore, current evidence does not support treatment benefit of Omega-3 fatty acids in preventing atrial fibrillation recurrence among patients who have not been treated by any conventional reversion treatment, or who have only been treated with pharmacological therapy.

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.

Effect of eicosapentaenoic acid and pitavastatin on electrophysiology and anticoagulant gene expression in mice with rapid atrial pacing

Atrial remodeling is considered to be any persistent change in atrial structure or function, and is responsible for the development and perpetuation of atrial fibrillation (AF). Oxidative stress and intracellular pH regulation may also be linked to AF; however it remains unclear whether eicosapentaenoic acid (EPA) or statins have beneficial therapeutic effects. The aim of the present study was to investigate the effects of EPA and pitavastatin on the electrophysiology of and gene expressions in mice with rapidly-paced atria. Mice were treated with EPA (10 mg/g/day) or pitavastatin (30 ng/g/day) for 6 weeks, following which AF was simulated by 8-h atrial pacing at 1,800 bpm. The atrial electrophysiological properties and the expression of cardiac genes, potassium voltage-gated channel subfamily A member 5 (Kcna5), Kcn subfamily D member 2 (Kcnd2), Kv channel-interacting protein 2 (KChIP2), solute carrier family 9 member A1, thrombomodulin (TM) and tissue factor pathway inhibitor (TFPI) were examined using reverse transcription-quantitative polymerase chain reaction. In control mice, significant atrial electrical remodeling was observed (P<0.05); however, treatment with either EPA or pitavastatin ameliorated these electrophysiological changes (P>0.05). mRNA levels of Kcnd2, KChIP2 and Kcna5 were significantly upregulated in control mice (P<0.05), whereas treatment with EPA or pitavastatin attenuated this upregulation (P>0.05). Administration of pitavastatin significantly reduced the downregulation of both TFPI and TM (P<0.05). EPA treatment attenuated the TFPI downregulation compared with control mice (P>0.05), however no significant effect on TM expression was observed. In addition, both EPA (P>0.05) and pitavastatin (P<0.05) suppressed the overexpression of endothelial nitric oxide synthase. This was also exhibited in Ras-related C3 botulinum toxin substrate 1 genes (P<0.01 for both treatments). In conclusion, the results of the present study suggested that EPA and pitavastatin are able to prevent atrial electrical remodeling, thrombotic states and oxidative stress in rapidly-paced murine atria.

Rabbit models of cardiac mechano-electric and mechano-mechanical coupling

Cardiac auto-regulation involves integrated regulatory loops linking electrics and mechanics in the heart. Whereas mechanical activity is usually seen as 'the endpoint' of cardiac auto-regulation, it is important to appreciate that the heart would not function without feed-back from the mechanical environment to cardiac electrical (mechano-electric coupling, MEC) and mechanical (mechano-mechanical coupling, MMC) activity. MEC and MMC contribute to beat-by-beat adaption of cardiac output to physiological demand, and they are involved in various pathological settings, potentially aggravating cardiac dysfunction. Experimental and computational studies using rabbit as a model species have been integral to the development of our current understanding of MEC and MMC. In this paper we review this work, focusing on physiological and pathological implications for cardiac function.

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.

Novel therapeutic targets in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, contributing to increased morbidity and reduced survival through its associations with stroke and heart failure. AF contributes to a four- to fivefold increase in the risk of stroke in the general population and is responsible for 10-15 % of all ischemic strokes. Diagnosis and treatment of AF require considerable health care resources. Current therapies to restore sinus rhythm in AF are suboptimal and are limited either by their pro-arrhythmic effects or by their procedure-related complications. These limitations have necessitated identification of newer therapeutic targets to expand the treatment options. There has been a considerable amount of research interest in investigating the mechanisms of initiation and propagation of AF. Despite extensive research focused on the pathogenesis of AF, a thorough understanding of various pathways mediating initiation and propagation of AF still remains limited. Research efforts focused on the identification of these pathways and molecular mediators have generated a great degree of interest for developing more targeted therapies. This review discusses the potential therapeutic targets and the results from experimental and clinical research investigating these targets.

MicroRNA-1 accelerates the shortening of atrial effective refractory period by regulating KCNE1 and KCNB2 expression: an atrial tachypacing rabbit model

Background

The potential mechanisms of microRNA-1 (miR-1) in the electrical remodeling of atrial fibrillation remain unclear. The purpose of this study was to evaluate the effects of miR-1 on the atrial effective refractory period (AERP) in a right atrial tachypacing model and to elucidate the potential mechanisms.

Methods and Results

QRT-PCR and western blot were used to detect the expression of the miR-1, KCNE1, and KCNB2 genes after 1-week of right atrial tachypacing in New Zealand white rabbits. The AERP was measured using a programmable multichannel stimulator, and atrial fibrillation was induced by burst stimulation invivo. The slowly activating delayed rectifier potassium current (IKs) and AERP in atrial cells were measured by whole cell patch clamp invitro. Right atrial tachypacing upregulated miR-1 expression and downregulated KCNE1 and KCNB2 in this study, while the AERP was decreased and the atrial IKs increased. The downregulation of KCNE1 and KCNB2 levels was greater when miR-1 was further upregulated through invivo lentiviral infection. Electrophysiological tests indicated a shorter AERP, a great increase in the IKs and a higher atrial fibrillation inducibility. In addition, similar results were found when the levels of KCNE1 and KCNB2 were downregulated by smallinterferingRNA while keeping miR-1 level unaltered. Conversely, knockdown of miR-1 by anti-miR-1 inhibitor oligonucleotides alleviated the downregulation of KCNE1 and KCNB2, the shortening of AERP, and the increase in the IKs. KCNE1 and KCNB2 as the target genes for miR-1 were confirmed by luciferase activity assay.

Conclusions

These results indicate that miR-1 accelerates right atrial tachypacing-induced AERP shortening by targeting potassium channel genes, which further suggests that miR-1 plays an important role in the electrical remodeling of atrial fibrillation and exhibits significant clinical relevance as a potential therapeutic target for atrial fibrillation.

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.

Role of Long-Chain Omega-3 Fatty Acids in Psychiatric Practice

Nutrition plays a minor role in psychiatric practice which is currently dominated by a pharmacological treatment algorithm. An accumulating body of evidence has implicated deficits in the dietary essential long-chain omega-3 (LCn-3) fatty acids, eicosapenaenoic acid (EPA) and docosahexaenoic acid (DHA), in the pathophysiology of several major psychiatric disorders. LCn-3 fatty acids have an established long-term safety record in the general population, and existing evidence suggests that increasing LCn-3 fatty acid status may reduce the risk for cardiovascular disease morbidity and mortality. LCn-3 fatty acid supplementation has been shown to augment the therapeutic efficacy of antidepressant, mood-stabilizer, and second generation antipsychotic medications, and may additionally mitigate adverse cardiometabolic side-effects. Preliminary evidence also suggests that LCn-3 fatty acid supplementation may be efficacious as monotherapy for primary and early secondary prevention and for perinatal symptoms. The overall cost-benefit ratio endorses the incorporation of LCn-3 fatty acids into psychiatric treatment algorithms. The recent availability of laboratory facilities that specialize in determining blood LCn-3 fatty acid status and emerging evidence-based consensus guidelines regarding safe and efficacious LCn-3 fatty acid dose ranges provide the infrastructure necessary for implementation. This article outlines the rationale for incorporating LCn-3 fatty acid treatment into psychiatric practice.

The use of ω-3 poly-unsaturated fatty acids in heart failure: a preferential role in patients with diabetes

PURPOSE

To review the evidence for a beneficial effect of ω-3 PUFAs in heart failure (HF) and its co-morbidities, their possible preferential effect in diabetes and the potential mechanism for their benefit.

METHODS

We summarize the clinical studies which investigated the use of ω-3 PUFAs in patients with HF with an emphasis on diabetes. We briefly summarize the evidence for an effect of ω-3 PUFAs in patients with coronary artery disease (CAD), atrial fibrillation (AF) and ventricular arrhythmias. We also discuss the proposed mechanisms of ω-3 PUFA action in cardiovascular diseases.

RESULTS

While there is emerging evidence for a beneficial effect of ω-3 PUFA supplementation in patients with HF, the evidence for other indications have been variable and conflicting. In HF patients with diabetes, ω-3 PUFAs may have a preferential therapeutic benefit. Randomized controlled trials did not show considerable beneficial effects of ω-3 PUFAs in other conditions such as CAD and AF. In a diabetic and insulin-resistant state, ω-3 PUFAs bind to the G-protein coupled receptor, GPR120, resulting in reduced cytokine production from inflammatory macrophages and improved signaling in adipocytes, leading to a reduction in insulin resistance.

CONCLUSIONS

There is promising evidence showing that use of ω-3 PUFA supplementation improves clinical outcomes of HF patients with diabetes. Further clinical trials are needed in this regard.

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.

Omega-3 PUFAs and atrial fibrillation: have we made up our mind yet?

Atrial fibrillation (AF) is the most common type of arrhythmia in adults, accounting for about one third of total arrhythmia-related hospitalizations. AF impact on daily clinical practice is steadily rising, together with population aging and increased survival from underlying conditions closely associated with AF such as coronary heart disease and heart failure. Although antiarrhythmic therapy, oral anticoagulation, implanted device therapy, and ablation techniques are now all common and promptly available strategies in AF management, some of them are burdened by a low efficacy rate, while others are associated with increased proarrhythmic or hemorrhagic risk. Consequently, useful alternatives are being sought. Between those, polyunsaturated fatty acids (n-3 PUFAs) have risen from mere alternative to statins in dyslipidemia management to powerful and well-tolerated antiinflammatory, antithrombotic, and antiarrhythmogenic drugs. From the evidence collected through basic science studies, whether on in vivo myocytes, animal models, or surrogate end points in human, n-3 PUFAs seem to offer innumerable advantages. On the other hand, epidemiological and clinical trials failed to demonstrate a clear efficacy of n-3 PUFAs as antiarrhythmic drugs, although covered by an optimal safety profile. The aim of the present review is to summarize the most important evidences currently available on the role of n-3 PUFA in AF management and therapy.

Docosahexaenoic Acid, but Not Eicosapentaenoic Acid, Supplementation Reduces Vulnerability to Atrial Fibrillation

Background—

The potential health benefits of ω-3 polyunsaturated fatty acids (PUFAs) usually are studied using a combination of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). This combination reduces vulnerability to experimentally induced atrial fibrillation (AF). It is unknown whether EPA and DHA have differential effects when taken alone. Using a model of pacing-induced atrial hemodynamic overload, we investigated the individual effects of EPA and DHA on vulnerability to AF and atrial remodeling.

Methods and Results—

Thirty-four dogs were randomized into 3 groups, all of which underwent simultaneous atrial and ventricular pacing at 220 beats per minute for 14 days. One group received purified DHA (≈1 g/d) orally for 21 days beginning 7 days before pacing began. Similarly, 1 group received ≈1 g/d purified EPA. In a third (control) group (No-PUFAs), 8 dogs received ≈1 g/d olive oil, and 12 were unsupplemented. Electrophysiological and echocardiographic measurements were taken at baseline and 21 days. Atrial tissue samples were collected at 21 days for histological and molecular analyses. Persistent AF inducibility was significantly reduced by DHA compared with No-PUFAs median [25–75 percentiles], 0% [0%–3%] for DHA versus 3.1% [2.2%–11%] for No-PUFAs; P =0.007) but not by EPA (3.4% [1.9%–8.9%]). DHA also reduced atrial fibrosis compared with No-PUFAs (11±6% versus 20±4%, respectively; P <0.05), whereas EPA did not (15±5%; P >0.05).

Conclusions—

DHA is more effective than EPA in attenuating AF vulnerability and atrial remodeling in structural remodeling–induced 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).

Effect of Omega-3 Polyunsaturated Fatty Acid Supplementation in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained atrial arrhythmia conferring a higher morbidity and mortality. Despite the increasing incidence of AF; available therapies are far from perfect. Dietary fish oils, containing omega 3 fatty acids, also called polyunsaturated fatty acid [PUFA] have demonstrated beneficial electrophysiological, autonomic and anti-inflammatory effects on both atrial and ventricular tissue. Multiple clinical trials, focusing on various subsets of patients with AF, have studied the role of PUFA and their potential role in reducing the incidence of this common arrhythmia. While PUFA appears to have a beneficial effect in the primary prevention of AF in the elderly with structural heart disease, this benefit has not been universally observed. In the secondary prevention of AF, PUFA seems to have a greater impact in the reducing AF in patients with paroxysmal or persistent AF, stages of AF associated with less atrial fibrosis and negative structural remodeling. However, AF suppression has not been consistently demonstrated in clinical trials. In patients undergoing heart surgery, increasing PUFA intake has yielded mixed results in terms of AF prevention post-operatively; however, increased PUFA has been associated with a reduction in hospital stay. Therefore recommending the use of PUFA for the purpose of AF reduction remains controversial. This is in part attributable to the complexity of AF. Other conflicting variables include: heterogeneous patient populations studied; variable dosing; duration of follow-up; comorbidities; and, concomitant pharmacotherapy. This review article reviews in detail available basic and clinical research studies of fish oil in the treatment of AF, and its role in the treatment of this common disorder.

ABBREVIATIONS

AF=Atrial fibrillation, CHS=Cardiovascular Health Study,CABG=Coronary artery bypass surgery, d=Day, DHA=Docosahexaenoic acid, EPA=Eicosapentaenoic acid, ERP= Effective refractory period, g=Gram, PAF= Paroxysmal atrial fibrillation, PeAF= Persistent atrial fibrillation PUFA= Polyunsaturated fatty acid.

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.

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.

n-3 polyunsaturated fatty acids in the prevention of atrial fibrillation recurrences after electrical cardioversion: a prospective, randomized study

BACKGROUND

n-3 polyunsaturated fatty acids (n-3 PUFAs) exert antiarrhythmic effects and reduce sudden cardiac death. However, their role in the prevention of atrial fibrillation remains controversial. We aimed to determine the effect of n-3 PUFAs in addition to amiodarone and a renin-angiotensin-aldosterone system inhibitor on the maintenance of sinus rhythm after direct current cardioversion in patients with persistent atrial fibrillation.

METHODS AND RESULTS

We conducted a randomized, double-blind, placebo-controlled, parallel-arm trial in patients with persistent atrial fibrillation, with at least 1 relapse after cardioversion, and treated with amiodarone and a renin-angiotensin-aldosterone system inhibitor. Participants were assigned to placebo or n-3 PUFAs 2 g/d and then underwent direct current cardioversion 4 weeks later. The primary end point was the probability of maintenance of sinus rhythm at 1 year after cardioversion. Of 254 screened patients, 199 were found to be eligible and randomized. At the 1-year follow up, the probability of maintenance of sinus rhythm was significantly higher in the n-3 PUFAs-treated patients compared with the placebo group (hazard ratio, 0.62 [95% confidence interval, 0.52 to 0.72] and 0.36 [95% confidence interval, 0.26 to 0.46], respectively; P=0.0001).

CONCLUSIONS

In patients with persistent atrial fibrillation on amiodarone and a renin-angiotensin-aldosterone system inhibitor, the addition of n-3 PUFAs 2 g/d improves the probability of the maintenance of sinus rhythm after direct current cardioversion. Our data suggest that n-3 PUFAs may exert beneficial effects in the prevention of atrial fibrillation recurrence. Further studies are needed to confirm and expand our findings. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT01198275.

Effects of chronic omega-3 polyunsaturated fatty acid supplementation on human pulmonary vein and left atrial electrophysiology in paroxysmal atrial fibrillation

Omega-3 polyunsaturated fatty acids in fish oils may have antifibrillatory effects; however, their electrophysiologic effects in paroxysmal atrial fibrillation (PAF) remain unknown. The aim of this study was to investigate the effects of chronic fish oil supplementation on human pulmonary vein (PV) and left atrial electrophysiology in PAF. Patients with PAF undergoing PV isolation were randomized ≥1 month before their procedure into a control group (n = 18) or a fish oil group (n = 18) in an unblinded fashion. The latter were supplemented with fish oil 6 g/day for a mean of 40 ± 12 days. Pulmonary venous and left atrial effective refractory periods (ERPs), PV conduction, and susceptibility to AF initiated within PVs were assessed. Compared to the control group, the fish oil group had (1) longer left-sided (p = 0.002) and right-sided (p = 0.001) pulmonary venous ERPs; (2) less dispersion of pulmonary venous ERPs (left PVs p = 0.001, right PVs p = 0.07); (3) longer left atrial ERPs (p = 0.02); (4) no difference in pulmonary venous conduction; (5) lower incidence of AF initiated from PVs during ERP testing (77% vs 31%, p = 0.02); and (6) prolongation of mean AF cycle length (p = 0.009) and shortest AF cycle length in PVs (p = 0.04). In conclusion, patients with PAF chronically supplemented with fish oils exhibit distinctive electrophysiologic properties including prolonged pulmonary venous and left atrial ERPs and decreased susceptibility to initiation AF from within PVs. These changes may in part explain the antifibrillatory effect of chronic omega-3 polyunsaturated fatty acid supplementation in patients with PAF.

Upstream therapies for management of atrial fibrillation: review of clinical evidence and implications for European Society of Cardiology guidelines. Part I: primary prevention

Atrial fibrillation (AF) is associated with significant morbidity and mortality. It is also a progressive disease secondary to continuous structural remodelling of the atria due to AF itself, to changes associated with ageing, and to deterioration of underlying heart disease. Current management aims at preventing the recurrence of AF and its consequences (secondary prevention) and includes risk assessment and prevention of stroke, ventricular rate control, and rhythm control therapies including antiarrhythmic drugs and catheter or surgical ablation. The concept of primary prevention of AF with interventions targeting the development of substrate and modifying risk factors for AF has emerged as a result of recent experiments that suggested novel targets for mechanism-based therapies. Upstream therapy refers to the use of non-antiarrhythmic drugs that modify the atrial substrate- or target-specific mechanisms of AF to prevent the occurrence or recurrence of the arrhythmia. Such agents include angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), statins, n-3 (ω-3) polyunsaturated fatty acids, and possibly corticosteroids. Animal experiments have compellingly demonstrated the protective effect of these agents against electrical and structural atrial remodelling in association with AF. The key targets of upstream therapy are structural changes in the atria, such as fibrosis, hypertrophy, inflammation, and oxidative stress, but direct and indirect effects on atrial ion channels, gap junctions, and calcium handling are also applied. Although there have been no formal randomized controlled studies (RCTs) in the primary prevention setting, retrospective analyses and reports from the studies in which AF was a pre-specified secondary endpoint have shown a sustained reduction in new-onset AF with ACEIs and ARBs in patients with significant underlying heart disease (e.g. left ventricular dysfunction and hypertrophy), and in the incidence of AF after cardiac surgery in patients treated with statins. In the secondary prevention setting, the results with upstream therapies are significantly less encouraging. Although the results of hypothesis-generating small clinical studies or retrospective analyses in selected patient categories have been positive, larger prospective RCTs have yielded controversial, mostly negative, results. Notably, the controversy exists on whether upstream therapy may impact mortality and major non-fatal cardiovascular events in patients with AF. This has been addressed in retrospective analyses and large prospective RCTs, but the results remain inconclusive pending further reports. This review provides a contemporary evidence-based insight into the role of upstream therapies in primary (Part I) and secondary (Part II) prevention of AF.

Differential effects of antipsychotic medications on polyunsaturated fatty acid biosynthesis in rats: Relationship with liver delta6-desaturase expression

Polyunsaturated fatty acids (PUFA), a lipid family comprised of omega-3 (n-3) and n-6 fatty acids, are a critical component of cellular membranes, and recent in vitro studies have found that antipsychotic medications up-regulate genes responsible for PUFA biosynthesis. To evaluate this effect in vivo, rats were treated with risperidone (1.5, 3, 6mg/kg/day), paliperidone (1.5, 3, 6mg/kg/day), olanzapine (2.5, 5, 10mg/kg/day), quetiapine (5, 10, 20mg/kg/day), haloperidol (1, 3mg/kg/day) or vehicle through their drinking water for 40day. Effects on liver Fads1, Fads2, Elovl2, and Elovl5 mRNA expression, plasma indices of n-3 (plasma 22:6/18:3 and 20:5/18:3 ratios) and n-6 (plasma 20:4/18:2 and 20:3/18:2 ratios) biosynthesis, and peripheral (erythrocyte, heart) and central (frontal cortex) membrane PUFA composition were determined. Only risperidone and its metabolite paliperidone significantly and selectively up-regulated liver delta-6 desaturase (Fads2) mRNA expression, and robustly increased plasma indices of n-3 and n-6 fatty acid biosynthesis. In risperidone- and paliperidone-treated rats, plasma indices of n-3 and n-6 fatty acid biosynthesis were all positively correlated with liver Fads2 mRNA expression, but not Fads1, Elovl2, or Elovl5 mRNA expression. All antipsychotics at specific doses increased erythrocyte docosahexaenoic acid (DHA, 22:6n-3) composition, and all except quetiapine increased arachidonic acid (AA, 20:4n-6) composition. Risperidone, paliperidone, and olanzapine increased heart DHA and AA composition, and no antipsychotic altered frontal cortex DHA or AA composition. These in vivo data demonstrate that augmentation of PUFA biosynthesis is not common to all antipsychotic medications, and that risperidone and paliperidone uniquely increase delta-6 desaturase (Fads2) mRNA expression and most robustly increase PUFA biosynthesis and peripheral membrane composition.

Effects of chronic omega-3 polyunsaturated fatty acid supplementation on human atrial electrophysiology

BACKGROUND

Omega-3 polyunsaturated fatty acids in fish oils may have antifibrillatory effects. Their mechanism of action in humans is poorly understood.

OBJECTIVE

The purpose of this study was to investigate the effects of chronic fish oil supplementation on human atrial electrophysiology (EP).

METHODS

Two groups of patients without clinical AF or structural heart disease and fish intake ≤1/week were prospectively recruited into a control group (n = 30) and a fish oil group (n = 31). The latter were prescribed 6 g/day of fish oil for ≥1 month before an EP study. The following were compared at time of EP study: serum omega-3 levels; right atrial and coronary sinus effective refractory periods (ERPs); interatrial, intra-atrial, left atrial, and coronary sinus conduction at baseline and the maximal conduction delay with the shortest propagated extrastimulus; and inducibility of AF (10 inductions/patient).

RESULTS

The following significant differences were noted favoring the fish oil group at time of EP: (1) twofold higher total omega-3 levels (P < .001); (2) lengthening of ERPs by 8%-14% at all measured sites and pacing cycle lengths (P < .05); (3) no effect on baseline interatrial, intra-atrial, left atrial, and coronary sinus conduction but a significant attenuation of maximal conduction delay (P < .05); (4) less inducible AF (AF ≥30 seconds: 24.2% vs. 7.9%; P < .001); (5) shorter mean duration of induced AF (P = .003); and (6) prolongation of induced AF cycle length (P < .001).

CONCLUSIONS

Chronic fish oil supplementation in humans prolongs atrial refractoriness and reduces vulnerability to inducible AF. These EP changes may explain the antifibrillatory effect of chronic fish oil ingestion.

Atrial protective effects of n-3 polyunsaturated fatty acids: a long-term study in ovine chronic heart failure

BACKGROUND

It has been suggested that omega-3 polyunsaturated fatty acids (n-3 PUFAs) may prevent the development of atrial fibrillation (AF).

OBJECTIVE

The purpose of this study was to evaluate the impact of these agents on development of the AF substrate in heart failure (HF).

METHODS

In this study, HF was induced by intracoronary doxorubicin infusions. Twenty-one sheep [7 with n-3 PUFAs treated HF (HF-PUFA), 7 with olive oil-treated HF controls (HF-CTL), 7 controls (CTL)] were studied. Open chest electrophysiologic study was performed with assessment of biatrial effective refractory period (ERP) and conduction. Cardiac function was monitored by magnetic resonance imaging. Atrial n-3 PUFAs levels were quantified using chromatography. Structural analysis was also performed.

RESULTS

Atrial n-3 PUFAs levels were twofold to threefold higher in the HF-PUFA group. n-3 PUFAs prevented the development of HF-related left atrial enlargement (P = .001) but not left ventricular/atrial dysfunction. Atrial ERP was significantly lower in the HF-PUFA group (P <.001), but ERP heterogeneity was unchanged. In addition, n-3 PUFAs suppressed atrial conduction abnormalities seen in HF of prolonged P-wave duration (P = .01) and slowed (P <.001) and heterogeneous (P <.05) conduction. The duration of induced AF episodes in HF-PUFA was shorter (P = .02), although AF inducibility was unaltered (P = NS). A 20% reduction of atrial interstitial fibrosis was seen in the HF-PUFA group (P <.05).

CONCLUSION

In this ovine HF study, chronic n-3 PUFAs use protected against adverse atrial remodeling by preventing atrial enlargement, fibrosis, and conduction abnormalities leading to shorter AF episodes despite lower ERP.

[New developments in the antiarrhythmic therapy of atrial fibrillation]

Atrial fibrillation, which is associated with a worsening of congestive heart failure symptoms, an increased rate of stoke, and increased mortality, is still difficult to treat. New therapies must not only increase effectiveness, but also have to have an improved safety profile, in order to avoid sodium channel block in the ventricle of older patients with atrial fibrillation, and also prevent electrical and morphological remodeling. Dronedarone is less effective compared to amiodarone, but has a better side effect profile which leads to fewer discontinuations of treatment. The atrial ion channels are specifically blocked by a number of prospective antiarrhythmic substances. The most advanced is the testing of vernakalant (RSD1235), which primarily suppresses the I(Kur) current. Ranolazine is a new antianginal substance which influences the atrial ion channels and leads to a significant reduction of atrial and more specifically ventricular tachyarrhythmias. A number of other drugs are in development. They will lead to a better understanding of which form of atrial fibrillation can be best treated with which antiarrhythmic agent.

n-3 polyunsaturated fatty acids for the prevention of arrhythmia recurrence after electrical cardioversion of chronic persistent atrial fibrillation: a randomized, double-blind, multicentre study

AIMS

Persistent atrial fibrillation (AF) often recurs after direct current electrical cardioversion (ECV). As several experimental and clinical studies suggest that n-3 polyunsaturated fatty acids (PUFAs) may have antiarrhythmic properties even at the atrial level, we aimed to evaluate whether oral supplementation with PUFAs, in addition to conventional antiarrhythmic drugs, could reduce the recurrence rate of the arrhythmia after ECV of persistent AF.

METHODS AND RESULTS

Two hundred and four patients (mean age 69.3 years, 33% females) with persistent AF were randomly assigned to receive 3 g/day of PUFAs until ECV and 2 g/day thereafter (104 patients) or placebo (100 patients) for 6 months, beginning at least 1 week before ECV. Selection of conventional antiarrhythmic prophylaxis was left to local medical advice. The cardiac rhythm was assessed by both trans-telephonic monitoring and clinical visits. Primary end-point was the recurrence rate of AF. Sinus rhythm was restored, either spontaneously or after ECV, in 187 patients (91.7%); 95 patients (91.4%) on PUFAs and 92 patients (92.0%) on placebo (P=not significant). AF relapsed in 56 (58.9%) of the PUFAs patients and in 47 (51.1%) of the placebo patients (P=0.28). The mean time to AF recurrence was 83±8 days in the PUFAs group and 106±9 days in the placebo group (P=0.29).

CONCLUSION

Our results do not support the hypothesis that, in patients undergoing ECV of chronic persistent AF, supplementation with PUFAs in addition to the usual antiarrhythmic treatment reduces recurrent AF.

Upstream effect for atrial fibrillation: still a dilemma?

Atrial fibrillation is the most common arrhythmia in clinical practice. Ion channel blocking agents are often characterized by limited long-term efficacy and several side effects. In addition, ablative invasive procedures are neither easily accessible nor always efficacious. The "upstream therapy," which includes angiotensin-converting enzyme inhibitors, aldosterone receptor antagonists, statins, glucocorticoids, and ω-3 poly-unsaturated fatty acids, targets arrhythmia substrate, influencing atrial structural and electrical remodeling that play an essential role in atrial fibrillation induction and maintenance. The mechanisms involved and the most important clinical evidence regarding the upstream therapy influence on atrial fibrillation are presented in this review. Some open questions are also proposed.