Use of irbesartan to maintain sinus rhythm in patients with long-lasting persistent atrial fibrillation: a prospective and randomized study

Novel Pharmacological Interventions to Maintain Sinus Rhythm after DC Cardioversion

Despite the availability of potentially curative interventions for atrial fibrillation, there remains an important role for conventional anti-arrhythmic therapy and anti-coagulation combined with direct current cardioversion. Unfortunately, the latter approach is disturbed by high recurrence rates of atrial fibrillation. In recent years, several adjunctive therapies have emerged which may facilitate the maintenance of sinus rhythm. These novel therapies and their potential mechanisms of action are reviewed in this article.

Atrial fibrillation in athletes

Atrial fibrillation (AF) is the most common arrhythmia in the athletic community and is more frequently observed in middle-aged than in young athletes. Recent studies have shown that the prevalence of AF is higher in individuals who are involved in intense short-term training and long-term sports participation compared to general population of the same age although clear evidence about the causal relation between these conditions is lacking. Anatomic adaptation, chronic systemic inflammation, and alterations in the autonomic system are all possible explanations for the increased prevalence of AF in athletes. AF associated with sports is usually paroxysmal with occasional crisis. Treatment of AF in this population can be challenging because of a lack of randomized trials and clear guidelines. Antiarrhythmic agents are usually the preferred choice of drugs. Several reports of catheter ablation have demonstrated encouraging results. Further studies are needed to understand the mechanism of autonomic hyperactivation and its interaction with the atrial substrate to develop new ablation strategies in this group of patients. Also, studies on the intensity and duration of exercise that would negate the proarrhythmic cardiac effects are also warranted.

Renin-Angiotensin System and AtrialFibrillation:Understanding the Connection

Atrial fibrillation (AF) arises as a result of a complex interaction of triggers, perpetuators and the substrate. The recurrence of AF may be partially related to a biologic phenomenon known as remodeling, in which the electrical, mechanical, and structural properties of the atrial tissue and cardiac cells are progressively altered,creating a more favorable substrate. Atrial remodeling is in part a consequence of arrhythmia itself. Therefore,to prevent and to treat AF, much attention has been directed to upstream therapies to alter the arrhythmia substrate and to reduce atrial remodeling. The renin-angiotensin-aldosterone system (RAAS) plays a keyrole in these strategies. In this review we analyze the experimental and clinical evidence regarding the efficacy of RAAS inhibitors in AF treatment. In the primary prevention of AF, meta-analyses have shown that risk of new-onset AF in patients with congestive heart failure and left ventricular dysfunction is reduced by RAAS inhibitors, whereas in hypertensive and post-myocardial infarction patients, the results are less evident. In the secondary prevention of AF, some large, prospective, randomized, placebo-controlled studieswith angiotensin II-receptor blockers returned negative results. Unfortunately, the approach of using RAASinhibitors as antiarrhythmic drugs to prevent both new-onset and recurrent AF is in decline because negativetrial results are accumulating, with the exception of the results in patients with congestive heart failure.

Hypertension and atrial fibrillation: epidemiology, pathophysiology and therapeutic implications

Hypertension is one of the most important risk factors associated with atrial fibrillation (AF) and increased the risk of cardiovascular events in patients with AF. However, the pathophysiological link between hypertension and AF is unclear. Nevertheless, this can be explained by the hemodynamic changes of the left atrium secondary to long standing hypertension, resulting in elevated left atrium pressure and subsequently left atrial enlargement. Moreover, the activation of renin-angiotensin-aldosterone system (RAAS) activation in patients with hypertension induces left atrial fibrosis and conduction block in the left atrium, resulting in the development of AF. Accordingly, recent studies have shown that effective blockage of RAAS by angiotensin converting enzyme inhibitors or angiotensin receptor antagonist may be effective in both primary and secondary prevention of AF in patients with hypertension, although with controversies. In addition, optimal antithrombotic therapy, blood pressure control as well as rate control for AF are key to the management of patients with AF.

Left atrial function assessed by speckle tracking echocardiography as a predictor of new-onset non-valvular atrial fibrillation: results from a prospective study in 580 adults

AIMS

The aim of this prospective study was to evaluate left atrial (LA) function for the prediction of increased risk of new-onset non-valvular atrial fibrillation (AF). Risk stratification for new-onset AF based on LA remodelling may have a major public health impact. Although left atrial volume (LAV) or LA dimension have been proposed as predictors of AF, other predictive parameters of LA function have not yet been fully examined.

METHODS AND RESULTS

LA emptying function (EF), strain rate (SR), and LAV were evaluated in the apical four-chamber view by speckle tracking echocardiography in 580 consecutive adults (age 64 ± 17, 303 men) without a history of atrial arrhythmias. During a follow-up period of 28 months, 32 subjects (age 73 ± 9, 18 men) developed electrocardiographically confirmed AF. Subjects with new-onset AF had lower LA active EF (16 ± 5 vs. 28 ± 8%, P< 0.001) and lower LA SR at atrial contraction (-0.9 ± 0.2 vs. -1.4 ± 0.5 S(-1), P< 0.001), but larger maximum LAV index (59 ± 12 vs. 46 ± 16 mL/m(2), P< 0.001) compared with non-AF subjects at baseline. In multivariate logistic regression analysis, LA active EF was the only independent predictor of new-onset AF. Using an LA active EF cut-off of ≤20%, the sensitivity and specificity for new-onset AF based on receiver operator characteristic curve analysis were 88 and 81%, respectively (area under the curve: 0.92).

CONCLUSION

Reduced LA active EF (booster pump function) assessed by speckle tracking echocardiography independently predicts the risk of new-onset AF, suggesting a stronger association between LA functional remodelling and AF than between LA size and AF.

Primary stroke prevention and hypertension treatment: which is the first-line strategy?

Hypertension (HT) is considered the main classic vascular risk factor for stroke and the importance of lowering blood pressure (BP) is well established. However, not all the benefit of antihypertensive treatment is due to BP reduction per se, as the effect of reducing the risk of stroke differs among classes of antihypertensive agents. Extensive evidences support that angiotensin-converting enzyme inhibitors (ACEI), angiotensin II receptor blockers (ARB), dihydropyridine calcium channel blockers (CCB) and thiazide diuretics each reduced risk of stroke compared with placebo or no treatment. Therefore, when combination therapy is required, a combination of these antihypertensive classes represents a logical approach. Despite the efficacy of antihypertensive therapy a large proportion of the population, still has undiagnosed or inadequately treated HT, and remain at high risk of stroke. In primary stroke prevention current guidelines recommend a systolic/diastolic BP goal of <140/<90 mmHg in the general population and <130/80 mmHg in diabetics and in subjects with high cardiovascular risk and renal disease. The recent release in the market of the fixed-dose combination (FDC) of ACEI or ARB and CCB should provide a better control of BP. However to confirm the efficacy of the FDC in primary stroke prevention, clinical intervention trials are needed.

Atrial fibrillation and heart failure parallels: lessons for atrial fibrillation prevention

Heart failure (HF) and atrial fibrillation (AF) are 2 of the most common cardiovascular diseases encountered in clinical practice, and the prevalence of these diseases continues to grow worldwide with the aging of the global population. While recognizing that AF is a heterogeneous disorder, we submit that the parallels between AF and HF may arise because many cases of AF and HF result from the cumulative exposure of the atria and ventricles to a common set of systemic cardiovascular risk factors. Over time, exposure to risk factors promotes development of atrial and ventricular structural and functional abnormalities through activation of several biologic pathways in concert: upregulation of neurohormonal signaling cascades, release of inflammatory mediators, programmed cell death, and fibrosis. Cardiac structural remodeling occurs in concert with electrophysiologic remodeling, both of which contribute to atrial and ventricular rhythm disturbances, including AF. AF and HF, instead of representing distinct disease processes, often represent different endpoints along a disease continuum. By reviewing some of the mechanistic parallels between AF and HF, we hope to emphasize the connection between established cardiovascular risk factors, cardiac remodeling and AF, with a view to promote strategies for AF prevention.

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

Fundamental research into molecular mechanisms of atrial fibrillation (AF) and improved understanding of processes involved in the initiation and maintenance of AF have transformed the traditional approach to its management by targeting only the electrical aspects, usually with antiarrhythmic drugs and, recently, by ablation. The antiarrhythmic potential of upstream therapies, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers (ARBs), statins, and n-3 (ω-3) polyunsaturated fatty acids, extends beyond the benefit of treating underlying heart disease to modifying the atrial substrate and intervening in specific mechanisms of AF. The key target is structural remodelling of the atria, particularly inflammation and fibrosis, although there is evidence to suggest the direct involvement at the ion channel level. Positive clinical reports supported by robust experimental data have suggested that upstream therapies can be valuable strategies for primary prevention of AF in selected patients and have resulted in several class IIA recommendations in the new European guidelines on AF. However, these results have not been consistently replicated in the secondary prevention setting, and several recent randomized controlled studies failed to demonstrate any effect of upstream therapies on AF burden or on major cardiovascular outcomes. Part II of the review summarizes the evidence base for the use of upstream therapies for secondary prevention of AF.

Relationship between -344T/C polymorphism in the aldosterone synthase gene and atrial fibrillation in patients with essential hypertension

INTRODUCTION

Aldosterone plays an important role in the pathogenesis of non-familial atrial fibrillation (AF). We tested the hypothesis that the -344T/C polymorphism in the aldosterone synthase gene may be associated with non-familial AF in Chinese patients with hypertension.

MATERIALS AND METHODS

We performed a 1:1 paired case-control study in 310 cases of hypertension with AF and same number matched controls. The -344T/C polymorphism was determined with polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The distribution of the CYP11B2 genotypes (TT, TC and CC) was 41.9%, 50.6%, and 7.4% in AF patients, which was not different from controls (48.4%, 44.5%, and 7.1%, χ(2) = 2.675, p = 0.263). The difference between the C allele (32.3% vs. 29.4%) was also not significant between two groups (χ(2) = 1.661, p = 0.197). Logistic regression analysis showed that LAD and LVEDD (both p < 0.001), rather than the C allele of the CYP11B2 gene (p= 0.107) were significant predictors for AF. The LAD of C allele carriers is significantly larger than that of non-C allele carriers (p = 0.009).

CONCLUSIONS

Our results indicate that the -344T/C polymorphism in the aldostrone synthase gene is not associated with AF but it might be associated with atrial remodelling in hypertensives.

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.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers decrease the incidence of atrial fibrillation: a meta-analysis

BACKGROUND

There is not a general agreement regarding antiarrhythmic effects on atrial fibrillation (AF) of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs). This study was to assess whether ACEIs and ARBs could decrease the incidence of AF.

MATERIALS AND METHODS

Medline, Embase and Cochrane Library databases were searched for trials reported from 1950 to May 2009. Search terms included 'randomized controlled trial (RCT), controlled clinical trials, random allocation' and medical subject headings that included all spellings of ACEIs and ARBs agents, 'atrial fibrillation' and 'atrial flutter'. Randomized, controlled human trials of ACEIs or ARBs reporting AF were included. Data were extracted independently by two reviewers using a predefined data extraction sheet, including study quality indicators. Meta-analysis and subgroup analyses were carried out with a random effects model.

RESULTS

Twenty-one trials including 91,381 patients and 5730 AF events were identified. Overall, ACEIs/ARBs reduced the relative risk (c) of AF by 25%. In primary and secondary prevention, ACEIs/ARBs decreased the incidence of AF by 24% and 27%, respectively. Patients with hypertension (RR: 0·71, 95%CI: 0·54-0·92), patients with chronic heart failure (RR: 0·58, 95%CI: 0·39-0·87) and those with AF (RR: 0·71, 95%CI: 0·52-0·96) benefited from ACEIs/ARBs treatment.

CONCLUSIONS

ACEIs/ARBs are effective for primary prevention and secondary prevention of AF. They decrease the incidence of AF especially in patients with hypertension, patients with chronic heart failure and those with AF.

Clinical characteristics and cardiovascular outcomes of hemodialysis patients with atrial fibrillation: a prospective follow-up study

BACKGROUND/AIMS

Among the cardiovascular complications in dialysis patients, atrial fibrillation (AF) is the most common arrhythmia. The purpose of this study was to clarify the characteristics and mortality of hemodialysis patients with AF, which are not completely elucidated.

METHODS

The prevalence of AF in patients undergoing hemodialysis in our institutions was assessed. Patients with AF (AF group) and without AF (control group) were included in this study. Patients in the control group were matched for several important clinical risk factors. For further analysis, AF patients were divided into two groups on the basis of the type of AF (chronic AF (CAF) and paroxysmal AF (PAF) groups). These patients were evaluated for their clinical characteristics, laboratory data and echocardiographic parameters and prospectively followed up for 48 months.

RESULTS

Among 328 study patients, 30 had AF (9.1%). Left atrial diameter (LAD) and the left ventricular mass index were significantly greater in the AF group than in the control group. Furthermore, cardiovascular and all-cause mortality and cumulative incidence of cardiovascular events were significantly higher in the AF group than in the control group, and tended to be higher in the CAF group.

CONCLUSIONS

Our findings demonstrated that the prevalence of AF as 9.1% in hemodialysis patients, and that AF, especially CAF, were associated with high mortality.

Long-term use and tolerability of irbesartan for control of hypertension

In this review, we discuss the pharmacological and clinical properties of irbesartan, a noncompetitive angiotensin II receptor type 1 antagonist, successfully used for more than a decade in the treatment of essential hypertension. Irbesartan exerts its antihypertensive effect through an inhibitory effect on the pressure response to angiotensin II. Irbesartan 150-300 mg once daily confers a lasting effect over 24 hours, and its antihypertensive efficacy is further enhanced by the coadministration of hydrochlorothiazide. Additionally and partially beyond its blood pressure-lowering effect, irbesartan reduces left ventricular hypertrophy, favors right atrial remodeling in atrial fibrillation, and increases the likelihood of maintenance of sinus rhythm after cardioversion in atrial fibrillation. In addition, the renoprotective effects of irbesartan are well documented in the early and later stages of renal disease in type 2 diabetics. Furthermore, both the therapeutic effectiveness and the placebo-like side effect profile contribute to a high adherence rate to the drug. Currently, irbesartan in monotherapy or combination therapy with hydrochlorothiazide represent a rationale pharmacologic approach for arterial hypertension and early-stage and late-stage diabetic nephropathy in hypertensive type II diabetics.

Polymorphisms of the angiotensin-converting enzyme and angiotensinogen gene in patients with atrial fibrillation

Activation of the renin-angiotensin system (RAS) is associated with atrial fibrillation (AF). The aim of this study was to investigate the relation between AF and polymorphisms in RAS. One hundred and fifty patients with AF, 100 patients with no documented episode of AF and 100 healthy subjects were consecutively recruited into the study. The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism, and the M235T, A-20C, and G-6A polymorphisms of the angiotensinogen gene were genotyped. Patients with AF had significantly lower frequency of II genotype of ACE I/D and higher frequency of angiotensinogen M235T polymorphism T allele and TT genotype and G-6A polymorphism G allele and GG genotype compared with the controls. AF patients had significantly larger left atrium, higher left ventricular mass index (LVMI) and higher frequency of significant valvular pathology. ACE I/D polymorphism II genotype, angiotensinogen M235T polymorphism TT genotype and G allele and GG genotype of angiotensinogen G-6A polymorphism were still independently associated with AF when adjusted for left atrium, LVMI and presence of significant valvular pathology. Genetic predisposition might be underlying the prevalence of acquired AF. Patients with a specific genetic variation in the RAS genes may be more liable to develop AF.

New drugs vs. old concepts: a fresh look at antiarrhythmics

Common arrhythmias, particularly atrial fibrillation (AF) and ventricular tachycardia/fibrillation (VT/VF) are a major public health concern. Classic antiarrhythmic (AA) drugs for AF are of limited effectiveness, and pose the risk of life-threatening VT/VF. For VT/VF, implantable cardiac defibrillators appear to be the unique, yet unsatisfactory, solution. Very few AA drugs have been successful in the last few decades, due to safety concerns or limited benefits in comparison to existing therapy. The Vaughan-Williams classification (one drug for one molecular target) appears too restrictive in light of current knowledge of molecular and cellular mechanisms. New AA drugs such as atrial-specific and/or multichannel blockers, upstream therapy and anti-remodeling drugs, are emerging. We focus on the cellular mechanisms related to abnormal Na⁺ and Ca²⁺ handling in AF, heart failure, and inherited arrhythmias, and on novel strategies aimed at normalizing ionic homeostasis. Drugs that prevent excessive Na⁺ entry (ranolazine) and aberrant diastolic Ca²⁺ release via the ryanodine receptor RyR2 (rycals, dantrolene, and flecainide) exhibit very interesting antiarrhythmic properties. These drugs act by normalizing, rather than blocking, channel activity. Ranolazine preferentially blocks abnormal persistent (vs. normal peak) Na⁺ currents, with minimal effects on normal channel function (cell excitability, and conduction). A similar "normalization" concept also applies to RyR2 stabilizers, which only prevent aberrant opening and diastolic Ca²⁺ leakage in diseased tissues, with no effect on normal function during systole. The different mechanisms of action of AA drugs may increase the therapeutic options available for the safe treatment of arrhythmias in a wide variety of pathophysiological situations.

Lower levels of high-density lipoprotein cholesterol on admission and a recurrence of ischemic stroke: a 12-month follow-up of the Fukuoka Stroke Registry

BACKGROUND

Despite recent progress in treatments for secondary prevention, ischemic stroke recurs in 8% to 12% of stroke survivors. We investigated the predisposing factors associated with recurrence within the first 12 months after an ischemic event to explore more effective preventive strategies.

METHODS

Between June 2007 and April 2008, acute (within 7 days of onset) ischemic stroke patients were registered in the Fukuoka Stroke Registry (FSR), a multicenter, prospective, observational database. The clinical characteristics on admission were analyzed, and the patients were followed for 12 months.

RESULTS

Two hundred sixty patients (151 males and 109 females, 71 ± 11 years of age) were registered; 25 (9.6%) had recurrence of ischemic stroke during the follow-up period. Kaplan-Meier curve analysis revealed a significant difference in recurrence-free survival between patients with high-density lipoprotein (HDL) cholesterol <40 mg/dL on admission and those with HDL cholesterol ≥ 40 mg/dL (P = .042). Adjusted multivariate logistic regression analysis showed that age (odds ratio 1.06; 95% CI, 1.00-1.11; P = .035) and HDL cholesterol <40 mg/dL (odds ratio 2.73; 95% CI, 1.01-7.38; P = .048) on admission were independently associated with a recurrence of ischemic stroke within 12 months of the initial onset.

CONCLUSIONS

Aging and low HDL cholesterol levels are considered independent risk factors for a recurrence of ischemic stroke.

Update on the association of inflammation and atrial fibrillation

Atrial fibrillation (AF) is a common arrhythmia and is associated with significant morbidity and mortality. The pathogenesis of AF remains incompletely understood and management remains a difficult task. Over the past decade there has been accumulating evidence implicating inflammation in the pathogenesis of AF. Inflammation appears to play a significant role in the initiation and perpetuation of AF as well as the prothrombotic state associated with AF. Inflammatory biomarkers (C-reactive protein and interleukin-6) have been shown to be associated with the future development, recurrence and burden of AF, and the likelihood of successful cardioversion. Therapies directed at attenuating the inflammatory burden appear promising. Animal and clinical studies have evaluated statins, angiotensin-converting enzyme inhibitors/angiotensin-II receptor blockers, and corticosteroids for the treatment or prevention of AF. The purpose of this review is to provide current evidence on the relationship between inflammation and AF and potential therapies available to modulate the inflammatory state in AF.

Focus on renin-angiotensin system modulation and atrial fibrillation control after GISSI AF results

Atrial fibrillation is the most frequently encountered arrhythmia in clinical practice. Given that atrial fibrillation is steadily increasing and that the medium to long-term efficacy of antiarrhythmic drugs has proved poor, it is essential to seek new therapies to prevent its onset and to effectively control recurrences. The study of nonantiarrhythmic drugs that act on the atrial remodeling that constitutes the substrate of the arrhythmia is a new and very interesting field of research. In this regard, several molecules that interact with the renin-angiotensin system at the level of the enzymatic or receptor cascade have been investigated in the past 10 years; some results have been very promising, whereas others have been extremely disappointing. In particular, the publication in 2008 of the results of GISSI AF, a rigorously designed Italian prospective study conducted on a large number of patients, revealed no statistically significant differences between the active drug and a placebo in preventing arrhythmia recurrences. In this study, we reassess the rationale behind the use of this class of drugs for 'antiarrhythmic' purposes, re-examine the most significant results reported in the clinical literature since 1999 and discuss the results of the GISSI AF study in this light.

Inhibition of the renin-angiotensin system for prevention of atrial fibrillation

Atrial fibrillation (AF) is a source of considerable morbidity and mortality. There has been compelling evidence supporting the role of renin-angiotensin system (RAS) in the genesis and perpetuation of AF through atrial remodeling, and experimental studies have validated the utilization of RAS inhibition for AF prevention. This article reviews clinical trials on the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) for the prevention of AF. Results have been variable, depending on the clinical background of treated patients. ACEIs and ARBs appear beneficial for primary prevention of AF in patients with heart failure, whereas they are not equally effective in hypertensive patients with normal left ventricular function. Furthermore, the use of ACEIs or ARBs for secondary prevention of AF has been found beneficial only after electrical cardioversion. Additional data are needed to establish the potential clinical role of renin-angiotensin inhibition for prevention of AF.

The pharmaceutical pipeline for atrial fibrillation

Atrial fibrillation (AF) is associated with a significant burden of morbidity and increased risk of mortality. Beyond outstanding advances in catheter ablation procedures, antiarrhythmic drug therapy remains a corner-stone to restore and maintain sinus rhythm. However, potentially life-threatening hazards (proarrhythmia) and significant non-cardiac organ toxicity have made new drug development of prominent relevance. Multichannel blocking, atrial selectivity, and the reduction of the risk of adverse events have all constituted the main theme of modern antifibrillatory drug development. Dronedarone, an analog of amiodarone, has the unique characteristic of being the first antiarrhythmic drug demonstrated to reduce hospitalizations in AF. Dronedarone is associated with less systemic toxicity than amiodarone, although being less effective for sinus rhythm maintenance. Atrial selective agents have been developed to target ion channels expressed selectively in the atria. Among the most promising drugs of this class is vernakalant, which has been shown effective for the acute conversion of AF with small risk of proarrhythmia. Finally, increasing evidences support antiarrhythmic effectiveness of traditional non-antiarrhythmic drugs, such as renin-angiotensin system blockers, statins, and omega-3 fatty acids. In this article, we will focus on recent advances in antiarrhythmic therapy for AF, reviewing the possible clinical utility of novel antifibrillatory agents.

Prevention of recurrent atrial fibrillation with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers: a systematic review and meta-analysis of randomized trials

BACKGROUND

Controversy persists regarding the efficacy of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in the prevention of recurrent atrial fibrillation (AF). We performed a meta-analysis of randomized controlled trials (RCTs), not designed a priori to test this hypothesis, to explore whether ACEs and ARBs reduce recurrent AF.

METHODS

We performed a systematic literature search for RCTs using ACEIs or ARBs and providing data on the outcome of recurrent AF. Statistical heterogeneity across the trials was tested using the Cochran Q statistic and I(2) was computed to quantify heterogeneity. A 2-sided α error of less than .05 was considered statistically significant (P < .05).

RESULTS

The analysis was based on 8 RCTs including 2323 patients. The Mantel-Haenszel random-effect model was used to calculate relative risk (RR) for studies using ACEIs or ARBs, and for studies using ARBs. The fixed-effect model was used to calculate RR for studies using ACEIs. Meta-analysis of the studies revealed that ACEIs or ARBs significantly reduced the incidence of recurrent AF (RR, 0.611; 95% CI, 0.441-0.847; P = .003). The RR for recurrent AF was 0.643 (95% CI, 0.439-0.941; P = .023) for studies using ARBs and 0.54 (95% CI, 0.377-0.80; P = .002) for studies using ACEIs.

CONCLUSION

In this meta-analysis of RCTs not designed a priori to test the hypothesis, ACEs and ARBs were associated with a significant reduction in recurrent AF. Large-scale randomized trials designed a priori to test the hypothesis are necessary to complete the totality of evidence.

Management of atrial fibrillation: translating clinical trial data into clinical practice

Atrial fibrillation is a supraventricular tachyarrhythmia with significant consequences in terms of morbidity and mortality. In light of the limitations of available pharmacologic treatment options (suboptimal efficacy plus safety and tolerability issues), atrial fibrillation management should be individualized based on patient characteristics and comorbidities that could influence response to specific management approaches. The importance of adequate anticoagulation should not be overlooked. This review provides a practical guide for primary care physicians, internists, and cardiologists on current management strategies for atrial fibrillation, based on recent guidelines and current clinical data.

Sympathetic neurons express and secrete MMP-2 and MT1-MMP to control nerve sprouting via pro-NGF conversion

Recently, we have shown that high frequency electrical field stimulation (HFES) of sympathetic neurons (SN) induces nerve sprouting by up-regulation of nerve growth factor (NGF) which targets the tyrosine kinase A receptor (TrkA) in an autocrine/paracrine manner. There is increasing evidence that matrix metalloproteinase-2 (MMP-2) is not only involved in extracellular matrix (ECM) turnover but may also exert beneficial effects during neuronal growth. Therefore, this study aimed to investigate the regulation and function of MMP-2 and its major activator membrane type 1-matrix metalloproteinase (MT1-MMP) as well its inhibitor TIMP-1 in SN under conditions of HFES. Moreover, we analyzed molecular mechanisms of the beneficial effect of losartan, an angiotensin II type I receptor (AT-1)blocker on HFES-induced nerve sprouting. Cell cultures of SN from the superior cervical ganglia (SCG) of neonatal rats were electrically stimulated for 48 h with a frequency of 5 or 50 Hz. HFES increased MMP-2 and MT1-MMP mRNA and protein expression, whereas TIMP-1 expression remained unchanged. Under conditions of HFES, we observed a shift from pro- to active-MMP-2 indicating an increase in MMP-2 enzyme activity. Specific pharmacological MMP-2 inhibition contributed to an increase in pro-NGF amount in the cell culture supernatant and significantly reduced HFES-induced neurite outgrowth. Losartan abolished HFES-induced nerve sprouting in a significant manner by preventing HFES-induced NGF, MMP-2, and MT1-MMP up-regulation. In summary, specific MMP-2 blockade prevents sympathetic nerve sprouting (SNS) by inhibition of pro-NGF conversion while losartan abolishes HFES-induced SNS by reducing total NGF, MMP-2 and MT1-MMP expression.

Combined effects of up- and downstream therapies on atrial fibrillation in a canine rapid stimulation model

BACKGROUND

Recent reports suggest angiotensin receptor blockers (ARBs) and some antiarrhythmic agents affect atrial remodeling in atrial fibrillation (AF). We evaluated the effect of combination therapy with olmesartan (Olm) and bepridil (Bep) in a canine model of AF.

METHODS AND RESULTS

An atrial stimulation device was implanted in 10 dogs undergoing 6-week pacing at 400 bpm. They were divided into Olm (2 mg/kg/day) (n=5) and Olm+Bep (Olm, 2 mg/kg/day; Bep, 10 mg/kg/day) groups (n=5). Atrial effective refractory period (AERP), conduction velocity (CV), and AF inducibility were evaluated weekly, and hemodynamics, atrial histology, and mRNA expression and protein expression of ion-channel and gap junction-related molecules at 6 weeks. Data were compared between groups and with non-pacing control and pacing-control groups from our previous report. The pacing-control group exhibited shortened AERP, decreased CV, increased AF inducibility and tissue fibrosis, and down-regulated L-type Ca(2+) channel (LCC), SCN5A, Kv4.3 and connexin43 (Cx43). By comparison, the Olm group exhibited suppression of the decrease in CV and of the increase in AF inducibility, but no change in AERP shortening. The Olm+Bep group exhibited suppression of AERP shortening as well as the greatest decrease in AF inducibility. Histologically, tissue fibrosis was suppressed in Olm and Olm+Bep groups. Down-regulation of Cx43 was partly suppressed in the Olm group while that of LCC, SCN5A, and Cx43 was suppressed in the Olm+Bep group.

CONCLUSION

Olm and Bep in combination suppressed AF inducibility more strongly than Olm alone, and may be more useful in the suppression of AF.

Angiotensin II induces complex fractionated electrogram in a cultured atrial myocyte monolayer mediated by calcium and sodium-calcium exchanger

Angiotensin II (AngII) has been implicated in the mechanism of atrial fibrillation (AF). There may be calcium-dependent pro-fibrillatory effect of AngII on atrial myocytes. We used cultured confluent HL-1 atrial myocyte monolayer with spontaneously propagated depolarization to study direct pro-fibrillatory effect of AngII and its molecular mechanism. AngII stimulation induced fibrillatory-like complex electrogram and calcium wave propagation. AngII shortened action potential duration and augmented calcium transient, thus increasing electrochemical gradient of forward-mode sodium-calcium exchanger (NCX) current and induced frequent irregular afterdepolarizations. AngII increased expression of sodium-calcium exchanger (NCX), further increasing calcium-membrane voltage coupling gain. The fibrillatory effect of AngII was attenuated by NCX blocker SEA0400 and NCX siRNA knockdown. AngII increased expression of L-type calcium channel and augmented calcium transient through PKC and CREB. The fibrillatory effect of AngII was also attenuated by PKC inhibitor chelerythrine and dominant negative form of CREB. In conclusions, AngII itself may electrically contribute to the mechanism of AF through increasing NCX expression and augmenting calcium transient, which is PKC and CREB dependent. Specific genetic knockdown of NCX attenuated calcium mediated afterdepolarization and complex electrogram.

Tachycardia of atrial myocytes induces collagen expression in atrial fibroblasts through transforming growth factor β1

AIMS

We investigated the molecular mechanism of rapid-depolarization-induced atrial fibrosis.

METHODS AND RESULTS

We used a direct atrial myocyte-fibroblast contact co-culture and a fibroblast-specific transforming growth factor β1 (TGF-β1), connective tissue growth factor (CTGF) and procollagen type I α-1 (COL1A1) luciferase reporter system to investigate the possible molecular mechanism of rapid-depolarization-induced atrial fibrosis. Mouse atrial fibroblasts were first transfected with promoter-luciferase reporters, and then co-cultured with HL-1 atrial myocytes. Rapid depolarization of atrial myocytes by rapid electrical field stimulation induced increased TGF-β1, CTGF and COL1A1 promoter activities in the co-cultured atrial fibroblasts (2.4 ± 0.3-fold increase, P= 0.008 for TGF-β1; 2.9 ± 0.4-fold increase, P< 0.001 for CTGF; and 2.1 ± 0.2-fold increase, P= 0.008 for COL1A1). Rapid depolarization of atrial myocytes increased paracrine secretion of angiotensin II (Ang II) and reactive oxygen species in the co-culture medium. Rapid electrical field stimulation-induced ROS generation in atrial myocytes was attenuated by the membrane NADPH oxidase inhibitor, apocynin. Atrial myocyte-induced expression of TGF-β1, CTGF and COL1A1 in atrial fibroblasts was attenuated by co-treatment with the Ang II receptor blocker, losartan, and apocynin. Atrial myocyte-induced COL1A1 expression in atrial fibroblasts was attenuated by anti-TGF-β1 antibody and RNA interference knockdown of the TGF-β1 receptor.

CONCLUSION

We first demonstrated that tachycardia of atrial myocytes induced paracrine secretion of Ang II and reactive oxygen species, which in turn induced expression of CTGF and procollagen in co-cultured atrial fibroblasts through increasing TGF-β1 expression. The results may imply that use of an Ang II receptor blocker, in combination with an anti-oxidant, blocks rapid-depolarization-induced atrial fibrosis.

Remodeling of ion channel expression in patients with chronic atrial fibrillation and mitral valvular heart disease

BACKGROUND/AIMS

Underlying cardiac pathology and atrial fibrillation (AF) affect the molecular remodeling of ion channels in the atria. Changes in the expression of these molecules have not been demonstrated in Korean patients with mitral valvular heart disease. Thus, the purpose of this study was to analyze ion channel expression in patients with chronic AF and mitral valvular heart disease.

METHODS

A total of 17 patients (eight males and nine females; mean age, 57 ± 14 years [range, 19 to 77]) undergoing open-heart surgery were included in the study. Twelve patients (seven with coronary artery disease and five with aortic valvular disease) had sinus rhythm, and five patients (all with mitral valvular disease) had chronic, permanent AF. A piece of right atrial appendage tissue (0.5 g) was obtained during surgery. RT-PCR was used to evaluate the expression of L-type Ca(2+) channels, ryanodine receptor (RyR2), sarcoplasmic reticular Ca(2+)-ATPase (SERCA2), gene encoding the rapid component of the delayed rectifier I(kr) (HERG), gene encoding calcium-independent transient outward current I(to1) (Kv4.3), gene encoding the ultrarapid component of the delayed rectifier I(ku) (Kv1.5), K(+) channel-interacting protein 2 (KChIP2), hyperpolarization-activated cation channel 2 associated with the pacemaker current I(f) (HCN2), and gene encoding Na(+) channel (SCN5A).

RESULTS

Reduced L-type Ca(2+) channel, RyR2, SERCA2, Kv1.5, and KChIP2 expression and borderline increased HCN2 expression were observed in the patients with AF and mitral valvular heart disease. Left atrial diameter was negatively correlated with RyR2 and KChIP2 expression. Fractional area shortening of the left atrium was positively correlated with RyR2 and KChIP2 expression.

CONCLUSIONS

Alterations in ion channel expression and the anatomical substrate may favor the initiation and maintenance of AF in patients with mitral valvular heart disease.

[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.

Augmenting Maintenance of Sinus Rhythm in the Control of Atrial Fibrillation by Antiarrhythmic Drug Combinations

In recent years, a major development in the treatment of atrial fibrillation (AF) is the use of catheter ablation, and a significant number of patients may benefit from this mode of therapy. On a global scale, it may not be feasible to deal with most patients solely on the basis of ablation. Therefore, it is likely that much of the therapy for AF will continue to rely on antiarrhythmic agents for maintaining sinus rhythm. For many years, amiodarone and sotalol have been the dominant antiarrhythmic agents, with amiodarone being the most effective antiarrhythmic in suppressing AF; however, amiodarone use is limited due to concerns of end-organ toxicity. Upstream therapies, such as statins, fish oil, angiotensin converting enzyme (ACE) inhibitors, and angiotensin receptor blockers may also provide additive efficacy to these and other membrane-active antiarrhythmics. In recent years, a number of new agents are being developed and the first successful congener of amiodarone, dronedarone, has been shown to be effective in controlling AF and reducing cardiovascular hospitalization. This paper explores the possibility of augmenting the extent of controlling AF by combining multiple potent antiarrhythmic agents old and new.

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.

Relationship between the long-term preventive effect of combined treatment with antiarrhythmic drugs plus angiotensin-converting enzyme inhibitors and circadian variation in the onset of paroxysmal atrial fibrillation

We examined the relationship between the efficacy of combined treatment with antiarrhythmic drugs (AAD) plus enalapril for maintaining sinus rhythm and circadian variation in the onset of paroxysmal AF.Three hundred and forty-four patients with paroxysmal AF (239 men, mean age, 69 ± 11 years) who could be followed up ≥ 12 months were divided into 3 groups on the basis of circadian variation in the onset of AF: a diurnal group (7:00 AM-5:00 PM, n = 57), a nocturnal group (5:00 PM-7:00 AM, n = 108), and a mixed group (onset during both periods, n = 169). The maintenance rate of sinus rhythm during the follow-up period was compared between combined therapy (AAD plus enalapril) and AAD alone.In the diurnal group, the maintenance rates of sinus rhythm at 12, 36, 60, and 90 months were 100%, 100%, 100%, and 100%, respectively, for patients treated with AAD plus enalapril (n = 22) versus 97%, 91%, 89%, and 80% for patients treated with AAD alone (n = 35, P < 0.05). In the nocturnal group, the maintenance rates of sinus rhythm at 12, 36, 60, and 90 months were 96%, 96%, 96%, and 92%, respectively, in patients treated with AAD plus enalapril (n = 24) versus 100%, 100%, 100%, and 100% in patients treated with AAD alone (n = 84, P = NS). In the mixed group, maintenance rates of sinus rhythm at 12, 36, 60, and 90 months were 90%, 71%, 61%, and 57%, respectively, in patients treated with AAD plus enalapril (n = 49) versus 88%, 78%, 68%, and 61% in patients treated with AAD alone (n = 120, P = NS). Our findings suggest that the preventive efficacy of combined therapy with AAD plus enalapril is dependent on the timing of onset of paroxysmal AF, and this regimen seems to be most beneficial for the diurnal type of paroxysmal AF.

Atrial fibrillation-the final frontier

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and represents a significant health care issue. The diagnosis and management of AF uses a significant proportion of the health care budget and is responsible for substantial morbidity and mortality. Restoration and maintenance of sinus rhythm is still an important treatment option for symptomatic AF. Anti-arrhythmic drugs (AADs) have had inconsistent results for the prevention of recurrent AF and have been hampered by significant adverse effects. Catheter ablation has rapidly evolved and is fast becoming an alternative for AF prevention. Although multiple treatment options exist, no single modality is effective for all patients. This review outlines best current practice for AF prevention and future perspectives, focusing on new and promising developments in antiarrhythmic drug therapy, strategies for ablation therapy, and forms of hybrid therapy that may offer improved outcomes in selected patients.

Candesartan decreases type III procollagen-N-peptide levels and inflammatory marker levels and maintains sinus rhythm in patients with atrial fibrillation

This study has evaluated whether candesartans prevent the recurrence of atrial fibrillation (AF) and decrease type III procollagen-N-peptide (PIIINP) levels. A total of 153 patients with AF were enrolled in this study. Three groups of patients were compared; candesartan group was treated with candesartan plus bepridil (n = 52); and carvedilol group with carvedilol plus bepridil (n = 51); and bepridil group with bepridil alone (n = 50). The primary end point was length of time to the recurrence of AF and all patients were ultimately followed-up for 730 days. Serum levels of the biomarkers were measured at baseline and after 24 months. Maintenance of sinus rhythm was achieved in 25 (50%) patients in bepridil group, 37 (73%) in candesartan group, and 34 (67%) in carvedilol group, giving a bepridil group/candesartan group hazard ratio of 0.36 (95% confidence interval 0.21-0.63; P = 0.03). Candesartan significantly decreased PIIINP levels at 24 months than at baseline in sinus rhythm group (0.57 +/- 0.02 vs. 0.64 +/- 0.05 U/mL, P = 0.04) and did not decrease PIIINP levels in the recurrence group. In conclusions, PIIINP might be related to the possibility of the atrial fibrosis for AF. However, further studies are needed to clarify the relationship between PIIINP and AF.