Nonantiarrhythmic drug therapy for atrial fibrillation

Left atrial epicardial adipose tissue is closely associated with left atrial appendage flow velocity in patients with nonvalvular atrial fibrillation

Epicardial adipose tissue (EAT) can play an important role in the occurrence and development of atrial fibrillation and stroke. In this study, we explored the relationship between left atrial epicardial adipose tissue (LA-EAT) and left atrial appendage flow velocity (LAA-FV) in patients with nonvalvular atrial fibrillation (NV-AF). A total of 145 patients with NV-AF who underwent their first radiofrequency ablation were enrolled. They underwent left aortopulmonary vein computed tomography angiography (CTA) and transesophageal echocardiography (TEE) before AF ablation. Left atrial (LA) electroanatomical mapping was performed intraoperatively to assess left atrial voltage. Univariate regression analysis showed that LAA-FV was lower in patients with a low voltage zone (LAA-FV; 35.02 ± 10.78 cm/s vs. 50.60 ± 12.17 cm/s, P < 0.001). A multiple linear regression model showed that the left atrial low voltage zone (β = − 0.311 P < 0.001), LA-EAT volume (β = − 0.256 P < 0.001), left atrial appendage shape (β = − 0.216 P = 0.041), LAVI (β = − 0.153 P = 0.041), and type of atrial fibrillation (paroxysmal vs. persistence) (β = − 0.146 P < 0.048) were independent predictors of LAA-FV. In NV-AF patients, the increase in LA-EAT volume is related to the decrease in LAA-FV.

Research Priorities in the Secondary Prevention of Atrial Fibrillation: A National Heart, Lung, and Blood Institute Virtual Workshop Report

There has been sustained focus on the secondary prevention of coronary heart disease and heart failure; yet, apart from stroke prevention, the evidence base for the secondary prevention of atrial fibrillation (AF) recurrence, AF progression, and AF-related complications is modest. Although there are multiple observational studies, there are few large, robust, randomized trials providing definitive effective approaches for the secondary prevention of AF. Given the increasing incidence and prevalence of AF nationally and internationally, the AF field needs transformative research and a commitment to evidenced-based secondary prevention strategies. We report on a National Heart, Lung, and Blood Institute virtual workshop directed at identifying knowledge gaps and research opportunities in the secondary prevention of AF. Once AF has been detected, lifestyle changes and novel models of care delivery may contribute to the prevention of AF recurrence, AF progression, and AF-related complications. Although benefits seen in small subgroups, cohort studies, and selected randomized trials are impressive, the widespread effectiveness of AF secondary prevention strategies remains unknown, calling for development of scalable interventions suitable for diverse populations and for identification of subpopulations who may particularly benefit from intensive management. We identified critical research questions for 6 topics relevant to the secondary prevention of AF: (1) weight loss; (2) alcohol intake, smoking cessation, and diet; (3) cardiac rehabilitation; (4) approaches to sleep disorders; (5) integrated, team-based care; and (6) nonanticoagulant pharmacotherapy. Our goal is to stimulate innovative research that will accelerate the generation of the evidence to effectively pursue the secondary prevention of AF.

Molecular Targets and Pathways Contributing to the Effects of Wenxin Keli on Atrial Fibrillation Based on a Network Pharmacology Approach

BACKGROUND

Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with high rates of mortality and morbidity. The traditional Chinese medicine Wenxin Keli (WXKL) can effectively improve clinical symptoms and is safe for the treatment of AF. However, the active substances in WXKL and the molecular mechanisms underlying its effects on AF remain unclear. In this study, the bioactive compounds in WXKL, as well as their molecular targets and associated pathways, were evaluated by systems pharmacology.

MATERIALS AND METHODS

Chemical constituents and potential targets of WXKL were obtained via the Traditional Chinese Medicine Systems Pharmacology (TCMSP). The TTD, DrugBank, DisGeNET, and GeneCards databases were used to collect AF-related target genes. Based on common targets related to both AF and WXKL, a protein interaction network was generated using the STRING database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGGs) pathway enrichment analyses were performed. Network diagrams of the active component-target and protein-protein interactions (PPIs) were constructed using Cytoscape.

RESULTS

A total of 30 active ingredients in WXKL and 219 putative target genes were screened, including 83 genes identified as therapeutic targets in AF; these overlapping genes were considered candidate targets for subsequent analyses. The effect of treating AF was mainly correlated with the regulation of target proteins, such as IL-6, TNF, AKT1, VEGFA, CXCL8, TP53, CCL2, MMP9, CASP3, and NOS3. GO and KEGG analyses revealed that these targets are associated with the inflammatory response, oxidative stress reaction, immune regulation, cardiac energy metabolism, serotonergic synapse, and other pathways.

CONCLUSIONS

This study demonstrated the multicomponent, multitarget, and multichannel characteristics of WXKL, providing a basis for further studies of the mechanism underlying the beneficial effects of WXKL in AF.

Oxidative stress and inflammation as central mediators of atrial fibrillation in obesity and diabetes

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans. Several risk factors promote AF, among which diabetes mellitus has emerged as one of the most important. The growing recognition that obesity, diabetes and AF are closely intertwined disorders has spurred major interest in uncovering their mechanistic links. In this article we provide an update on the growing evidence linking oxidative stress and inflammation to adverse atrial structural and electrical remodeling that leads to the onset and maintenance of AF in the diabetic heart. We then discuss several therapeutic strategies to improve atrial excitability by targeting pathways that control oxidative stress and inflammation.

The importance of the neutrophil-to-lymphocyte ratio in patients with hypertrophic cardiomyopathy

INTRODUCTION

Previous studies have demonstrated the predictive value of the neutrophil-to-lymphocyte ratio (NLR) in many cardiovascular disorders. The aim of this study was to assess whether NLR is associated with echocardiographic or electrocardiographic parameters, or with predicted five-year risk of sudden cardiac death (SCD), in patients with hypertrophic cardiomyopathy (HCM).

METHODS

This prospective observational study included 74 controls and 97 HCM patients. Three years of follow-up results for HCM patients were evaluated.

RESULTS

NLR was significantly higher in patients with fragmented QRS, ventricular tachycardia, and presyncope than in those without (p=0.031, 0.030, and 0.020, respectively). NLR was significantly higher in patients whose predicted five-year risk of SCD was more than 6% and whose corrected QT interval was greater than 440 ms (p=0.022 and 0.001, respectively). It was also significantly higher in patients whose left ventricular ejection fraction (LVEF) was <60% than in those with LVEF >60% (p=0.017).

CONCLUSION

NLR was significantly higher in patients with HCM compared to the control group. A high NLR is associated with a higher five-year risk of SCD in patients with HCM.

Connexin mutant embryonic stem cells and human diseases

Intercellular communication via gap junctions allows cells within multicellular organisms to share small molecules. The effect of such interactions has been elucidated using mouse gene knockout strategies. Although several mutations in human gap junction-encoding connexin (Cx) have been described, Cx mutants in mice do not always recapitulate the human disease. Among the 20 mouse Cxs, Cx26, Cx43, and Cx45 play roles in early cardiac or placental development, and disruption of the genes results in lethality that hampers further analyses. Embryonic stem cells (ESCs) that lack Cx43 or Cx45 have made analysis feasible in both in vitro differentiated cell cultures and in vivo chimeric tissues. The success of mouse ESCs studies is leading to the use of induced pluripotent stem cells to learn more about the pathogenesis of human Cx diseases. This review summarizes the current status of mouse Cx disruption models and ESC differentiation studies, and discusses their implication for understanding human Cx diseases.

Statin Therapy for Primary Prevention of Atrial Fibrillation: Guided by CHADS2/CHA2DS2VASc Score

Atrial fibrillation (AF) is the most common arrhythmia and is associated with increased cardiovascular morbidity and mortality. The anti-arrhythmic effect of statins on AF prevention appears to be highly significant in most clinical studies. However, some discrepancies do exist among different clinical studies. Different clinical settings and types of stains used may explain these differences between trials. The CHADS₂ and CHA₂DS₂VASc scoring systems have been used for stroke risk stratification in AF patients. The recent study suggested that these scores can also be used to guide statin therapy for AF prevention. Patients with higher scores had a higher risk of developing AF and gained more benefits from statins therapy than those with lower scores. This review article focused on the ability of these scores to predict AF prevention by statins.

Association between CHADS2 score and the preventive effect of statin therapy on new-onset atrial fibrillation in patients with acute myocardial infarction

OBJECTIVES

New-onset atrial fibrillation (AF) commonly occurs in patients with acute myocardial infarction (AMI). Data regarding the value of the CHADS2 score in patients hospitalized for AMI is limited. This study aimed to determine whether the CHADS2 score is associated with new-onset AF and if it can help identify the patients who will benefit most from statin use for the prevention of arrhythmia after AMI.

METHODS

A total of 724 consecutive AMI patients were enrolled in this study. The patients were divided into 3 groups according to their CHADS2 scores: group 1, score 0; group 2, score 1-2; and group 3, score 3-6. The study endpoint was an episode of new-onset AF that lasted more than 30 seconds during hospitalization at the coronary care unit.

RESULTS

Seventy-eight (10.8%) patients developed new-onset AF, and 273 (37.7%) were on a statin upon admission. The incidence of new-onset AF increased significantly from 5.8% in group 1 to 11.3% in group 2 and 14.3% in group 3 (χ(2) for linear trend, P = 0.017). Statin use (odds ratio [OR], 0.22; 95% CI, 0.06-0.85) and CHADS2 score (OR, 1.53; 95% CI, 1.02-2.28) were independent predictors of new-onset AF in AMI patients. Patients with CHADS2 score ≤2 had significantly reduced C-reactive protein level and lower risk of developing new-onset AF if they were taking statins (P < 0.05). Multivariate logistic regression analysis demonstrated the benefit of statin use for preventing new-onset AF in patients with CHADS2 scores ≤2 (OR, 0.34; 95% CI, 0.14-0.81).

CONCLUSIONS

The CHADS2 score is a convenient scoring system for predicting the incidence of new-onset AF and may help in identifying the patients who will benefit most from statin use for the prevention of arrhythmia after AMI.

[Non-antiarrhythmic drug therapy for the prevention of atrial fibrillation?]

In atrial fibrillation (AF), the absence of a clear benefit of a rhythm-control strategy over a rate-control strategy seen in recent trials may be due to the fact that many of the usual antiarrhythmic strategy have significant weaknesses. Besides research efforts to improve the efficacy and safety of conventional antiarrhythmic agents, therapies directed 'upstream'of the electrical aspects of AF, towards the underlying anatomical substrate and atrial remodelling, have been proposed as new pharmacological therapeutic approaches. Potential upstream therapies for AF comprise a variety of agents such as angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB), statins, N-3 polyunsaturated fatty acids and steroids. On the basis of experimental data, clinical studies have provided information on the potential of upstream therapy for the prevention of AF across a broad spectrum of cardiovascular patient groups. In patients with heart failure or hypertension, data are sufficient to support the use of ACEI or ARB as treatment that may decrease the risk of AF beyond their other beneficial effects. Similarly, it is highly possible that the use of statin in patients with a recognized indication may be associated with a benefit against AF. However, in most clinical settings, the evidence appears to be insufficient to drive changes in therapy management per se, and large-scale, randomized controlled trials with adequately defined endpoints are still needed. The results from these trials may help to understand the complex mechanisms that lead to AF, and may clarify the benefit-to-risk ratio of these new therapeutic approaches.

Non-antiarrhythmic drugs to prevent atrial fibrillation

Atrial fibrillation (AF) is the most frequent arrhythmia found in clinical practice. The majority of patients with AF are still candidates for antiarrhythmic drug treatment, not only for acute reversion to sinus rhythm but also for long-term treatment to prevent recurrences of AF. Currently available antiarrhythmic drugs, however, are unable to provide complete efficacy in all patients, and present problematic risks of proarrhythmia. The progressively increasing prevalence of AF supports the need to develop improved therapeutic approaches for the clinical management of arrhythmia. Accordingly, new treatment techniques aimed at suppressing the origin of the arrhythmogenic foci have been developed in the last decade. However, ablative treatments are only available for selected patients. Because of these factors, and also because primary prevention of AF should be our goal, the introduction of non-antiarrhythmic agents that could prevent both new-onset AF and recurrences of AF may eventually improve patient outcomes and reduce the incidence of this epidemic disease. The potential clinical value of these non-antiarrhythmic options is currently under active investigation. There is now clinical and experimental evidence that many drugs may have beneficial effects in preventing AF through several possible mechanisms. Non-antiarrhythmic drugs, such as ACE inhibitors and angiotensin receptor blockers, HMG-CoA reductase inhibitors (statins), corticosteroids, and N-3 polyunsaturated fatty acids may have a positive effect in patients with AF or in preventing AF in patients at risk.

Oxidative stress on pulmonary vein and left atrium arrhythmogenesis

BACKGROUND

Oxidative stress and pulmonary veins (PVs) play critical roles in the pathophysiology of atrial fibrillation. The purpose of the present study was to investigate whether oxidative stress and antioxidant agents can change the electrophysiological characteristics of the left atrium (LA) and PVs.

METHODS AND RESULTS

Conventional microelectrodes were used to record the action potentials (APs) in isolated rabbit PV and LA specimens before and after H(2)O(2) administration with or without ascorbic acid or N-mercaptopropionyl-glycine (N-MPG, a free radical .OH scavenger). H(2)O(2) (0.02 and 0.2 mmol/L) decreased the PV spontaneous rates from 2.0+/-0.1 Hz to 1.6+/-0.1 Hz, and 1.7+/-0.1 Hz (n=10, P<0.05), but H(2)O(2) (2 mmol/L) increased PV spontaneous rates from 2.0+/-0.1 Hz to 2.8+/-0.2 Hz. H(2)O(2) easily induced PV burst firing and early afterdepolarizations, but not in the LA. H(2)O(2) shortened the AP duration and increased the contractile force to a greater extent in the LA than in PVs. In addition, the H(2)O(2)-induced PV burst firing and increasing spontaneous rates were suppressed or attenuated by pretreatment with ascorbic acid (1 mmol/L) or N-MPG (10 mmol/L).

CONCLUSIONS

H(2)O(2) significantly changed the electrophysiological characteristics of PV and LA through activation of free radicals and may facilitate the occurrence of atrial fibrillation.

Use of vitamins C and E as a prophylactic therapy to prevent postoperative atrial fibrillation

Oxidative stress has been strongly involved in the underlying mechanism of atrial fibrillation, particularly in the arrhythmia occurring in patients undergoing cardiac surgery with extracorporeal circulation (postoperative atrial fibrillation). The ischemia/reperfusion injury thus occurring in the myocardial tissue contributes to the development of tissue remodeling, thought to be responsible for the functional heart impairment. Consequently, structural changes due to the cardiac tissue biomolecules attack by reactive oxygen and/or nitrogen species could account for functional changes in ion channels, transporters, membrane conductance, cytosolic transduction signals, and other events, all associated with the occurrence of arrhythmic consequences. The lack of success and significant side effects of anti-arrhythmic drugs have given rise to attempts aimed to develop alternative novel pharmacologic treatments. On this line, the biological properties of the antioxidant vitamins C and E suggest that they could decrease the vulnerability of the heart to the oxidative damage. Nevertheless, very few studies to assess their anti-arrhythmic effects have been reported in humans. The clinical and experimental evidence supporting the view that the pharmacological use of antioxidant vitamins could contribute to prevent postoperative atrial fibrillation is presented.

Atrial fibrillation in congestive heart failure: current management

Atrial fibrillation (AF) and congestive heart failure are common conditions and each predisposes to the development of the other. Basic research using animal models of the two conditions continues to yield insights that may improve therapies. The role of medical therapies aimed at the underlying structural changes in AF continues to be a subject of ongoing studies. Cardiac resynchronization therapy is effective in appropriately selected patients with both sinus rhythm and AF. Catheter ablation is emerging as a potential alternative to antiarrhythmic drug therapy, but large randomized trials will be needed to assess its role.

[Is resynchronization therapy necessary when optimizing right ventricular stimulation?]

Cardiac resynchronization therapy (CRT) using biventricular stimulation is hampered by coronary venous imponderabilities, complex implantation procedures, technical malfunctions and complications as well as disappointing responder rates. Despite its pathophysiological soundness and some initial success, the use of AV sequential pacing for the treatment of heart failure has been abandoned because right ventricular (RV) apical stimulation may be detrimental for cardiac mechanics, may worsen heart failure and may increase mortality. Attempts at avoiding desynchronizing effects and improving hemodynamics by pacing from alternative RV sites have been numerous but not convincing. Whether patients with left ventricular dysfunction or overt heart failure may benefit from pacing the RV outflow tract or septum, from dual site RV or His bundle stimulation instead of left ventricular based resynchronization is the topic of this review.

Clinical use of and future perspectives on antiarrhythmic drugs

Cardiac arrhythmias are associated with significant morbidity and mortality. Antiarrhythmic drug therapy was traditionally the mainstay of arrhythmia treatment; however, the limited efficacy and proarrhythmic potential of conventional antiarrhythmic drugs has generated interest in new approaches to the treatment of arrhythmias. Over the last decade, there has been improved characterization of the molecular pathways that culminate in arrhythmias. By analyzing mechanisms that increase susceptibility to arrhythmias in individuals with genetic syndromes, it might be possible to not only improve current therapies but also to develop novel approaches to treat and prevent common arrhythmias.

The potential role of thiazolidinediones in atrial fibrillation

Thiazolidinediones (TZDs) represent insulin sensitizing drugs that are being increasingly used for the treatment of type 2 diabetes. These agents have also pleiotropic properties that possibly contribute to their favorable cardiovascular effects. In particular, TZDs have anti-inflammatory and anti-oxidant potential while they modulate cardiovascular remodeling. On the other hand, atrial electrical and structural remodeling constitutes the substrate for atrial fibrillation (AF) development and perpetuation. Of note, inflammation and oxidative stress have been recently implicated in the pathogenesis of AF while non-channel blocking drugs with pleiotropic properties, including anti-inflammatory and anti-oxidant, seem to favorably affect atrial remodeling. It is therefore reasonable to assume that TZDs may have a role in the management of AF. Despite some limited observations, no study to date has examined the effect of TZDs therapy on AF development. In addition, the role of these agents in atrial remodeling has not been clarified yet.

Meta-analysis of association between C-reactive protein and immediate success of electrical cardioversion in persistent atrial fibrillation

Current evidence links atrial fibrillation (AF) to the inflammatory state. Also, increased C-reactive protein (CRP) levels have been associated with greater risk of recurrence of AF after successful electrical cardioversion (EC). We conducted a meta-analysis of observational studies to examine the association between baseline CRP levels and the immediate success of EC in persistent AF. We searched the literature published November 2007 or earlier. In addition, a manual search was performed using all review articles on this topic, reference lists of studies, and abstracts from conference reports. Of the 342 initially identified studies, 6 prospective observational studies with a combined 366 patients (297 with successful and 69 with failed EC) were analyzed. Overall, CRP levels were greater in patients with failed EC. The standardized mean difference in the CRP levels between patients with successful and those with failed EC was -0.41 units (95% confidence intervals -0.68 to -0.14) and the Z score for overall effect was 2.98 (p=0.003). The heterogeneity test showed that there were no significant differences between the individual studies (p=0.36; I(2)=9.1%). In conclusion, our meta-analysis suggests that increased CRP levels are associated with greater risk of EC failure. CRP assessment before cardioversion may provide prognostic information regarding the success of the procedure.

Astaxanthin: a novel potential treatment for oxidative stress and inflammation in cardiovascular disease

Oxidative stress and inflammation are implicated in several different manifestations of cardiovascular disease (CVD). They are generated, in part, from the overproduction of reactive oxygen species (ROS) and reactive nitrogen species (RNS) that activate transcriptional messengers, such as nuclear factor-kappaB, tangibly contributing to endothelial dysfunction, the initiation and progression of atherosclerosis, irreversible damage after ischemic reperfusion, and even arrhythmia, such as atrial fibrillation. Despite this connection between oxidative stress and CVD, there are currently no recognized therapeutic interventions to address this important unmet need. Antioxidants that provide a broad, "upstream" approach via ROS/RNS quenching or free radical chain breaking seem an appropriate therapeutic option based on epidemiologic, dietary, and in vivo animal model data. However, human clinical trials with several different well-known agents, such as vitamin E and beta-carotene, have been disappointing. Does this mean antioxidants as a class are ineffective, or rather that the "right" compound(s) have yet to be found, their mechanisms of action understood, and their appropriate targeting and dosages determined? A large class of potent naturally-occurring antioxidants exploited by nature-the oxygenated carotenoids (xanthophylls)-have demonstrated utility in their natural form but have eluded development as successful targeted therapeutic agents up to the present time. This article characterizes the mechanism by which this novel group of antioxidants function and reviews their preclinical development. Results from multiple species support the antioxidant/anti-inflammatory properties of the prototype compound, astaxanthin, establishing it as an appropriate candidate for development as a therapeutic agent for cardiovascular oxidative stress and inflammation.

A genetic framework for improving arrhythmia therapy

Abnormalities in heart rhythm continue to cause high rates of illness and death. Better treatment could be provided by solving two main challenges: the early identification of patients who are at risk, and the characterization of molecular pathways that culminate in arrhythmias. By analysing mechanisms that increase susceptibility to arrhythmia in individuals with genetic syndromes, it might be possible to improve current therapies and to develop new ways to treat and prevent common arrhythmias.

[His-bundle stimulation and alternative RV stimulation sites]

The increasing evidence that right ventricular (RV) apical stimulation is detrimental for cardiac mechanics and increases the risk of new onset heart failure and mortality promotes strategies to avoid ventricular pacing and - if not applicable due to atrioventricular block - stipulates the search for alternative techniques of pacing the heart from the right ventricle. Despite more than 15 years of clinical research it remains unclear whether pacing from the right ventricular outflow tract or septum, dual site RV stimulation or selective pacing of the His bundle results in hemodynamic and prognostic benefit over the traditional method of apical RV pacing. The article reviews pertinent literature and tries to demonstrate pathophysiological mechanisms.