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

Outcome of pharmacological rhythm control for new-onset persistent atrial fibrillation in patients with systolic heart failure: a comparison with patients with normal left ventricular function

AIMS

To compare outcome of a serial cardioversion strategy in atrial fibrillation (AF) patients with and without systolic heart failure (HF).

METHODS AND RESULTS

In patients with new-onset persistent AF and systolic HF [left ventricular ejection fraction (LVEF) <0.40] outcome of a serial electrical cardioversion (ECV) and serial antiarrhythmic drug strategy was compared with a control group of patients without HF. Follow-up was 18 months. Sixty-four consecutive patients with systolic HF (mean age 64 +/- 12 years, 50% coronary artery disease, LVEF 0.30 +/- 0.07) were enrolled and compared with 48 consecutive patients without HF (mean age 66 +/- 8 years, all LVEF >0.50, 40% lone AF). Success of ECV and occurrence of subacute and late recurrences in patients with and without HF were comparable. After the first relapse, AF was accepted in significantly more HF patients (23 vs. 4%, P < 0.01). Significantly less HF patients underwent serial ECV and antiarrhythmic drug approach (42 vs. 71%, respectively, P < 0.001). At the end of follow-up more HF patients were in permanent AF (45 vs. 29%, P = 0.03).

CONCLUSION

Recurrence pattern after ECV is comparable between patients with and without systolic HF, but outcome of a serial cardioversion strategy is worse in HF patients, possibly related to a less stringent use of this approach.

Losartan prevents stretch-induced electrical remodeling in cultured atrial neonatal myocytes

Atrial fibrillation (AF) is the most frequent arrhythmia found in clinical practice. In recent studies, a decrease in the development or recurrence of AF was found in hypertensive patients treated with angiotensin-converting enzyme inhibitors or angiotensin receptor-blocking agents. Hypertension is related to an increased wall tension in the atria, resulting in increased stretch of the individual myocyte, which is one of the major stimuli for the remodeling process. In the present study, we used a model of cultured atrial neonatal rat cardiomyocytes under conditions of stretch to provide insight into the mechanisms of the preventive effect of the angiotensin receptor-blocking agent losartan against AF on a molecular level. Stretch significantly increased protein-to-DNA ratio and atrial natriuretic factor mRNA expression, indicating hypertrophy. Expression of genes encoding for the inward rectifier K(+) current (I(K1)), Kir 2.1, and Kir 2.3, as well as the gene encoding for the ultrarapid delayed rectifier K(+) current (I(Kur)), Kv 1.5, was significantly increased. In contrast, mRNA expression of Kv 4.2 was significantly reduced in stretched myocytes. Alterations of gene expression correlated with the corresponding current densities: I(K1) and I(Kur) densities were significantly increased in stretched myocytes, whereas transient outward K(+) current (I(to)) density was reduced. These alterations resulted in a significant abbreviation of the action potential duration. Losartan (1 microM) prevented stretch-induced increases in the protein-to-DNA ratio and atrial natriuretic peptide mRNA expression in stretched myocytes. Concomitantly, losartan attenuated stretch-induced alterations in I(K1), I(Kur), and I(to) density and gene expression. This prevented the stretch-induced abbreviation of action potential duration. Prevention of stretch-induced electrical remodeling might contribute to the clinical effects of losartan against AF.

Polymorphism modulates symptomatic response to antiarrhythmic drug therapy in patients with lone atrial fibrillation

BACKGROUND

The angiotensin-converting enzyme (ACE) deletion allele, ACE D, is associated with increased ACE activity and adverse outcomes in cardiovascular disease. Although activation of the renin-angiotensin-aldosterone system (RAAS) now appears to play a role in the pathophysiology of atrial fibrillation (AF), it remains to be determined if ACE genotype impacts response to conventional AAD therapy in patients with AF.

OBJECTIVES

The purpose of this study was to investigate whether response to antiarrhythmic drug (AAD) therapy in patients with AF is modulated by the ACE I/D polymorphism.

METHODS

We studied 213 patients (147 men, 66 women; ages 52 +/- 15 years) prospectively enrolled in the Vanderbilt AF Registry. AAD therapy outcome was defined prospectively as response if there was a >or=75% reduction in symptomatic AF burden or nonresponse if AF burden was unchanged, necessitating a change in drugs or therapy.

RESULTS

Lone AF (age <65 years, no identifiable cause) was present in 72 (34%) patients, whereas hypertension was the most common underlying disease in the remaining 141 (41%). AF was paroxysmal in 170 (80%) and persistent in 43 (20%). The frequencies of the DD, ID, and II genotypes were in Hardy-Weinberg equilibrium. Lone AF and DD/ID genotypes were highly significant predictors of failure of drug therapy (P <.005). In patients with lone AF, failure of drug response was 5%, 41%, and 47% in patients with II, ID, and DD genotypes, respectively, (P <.005, II vs. ID/DD).

CONCLUSIONS

These results provide further evidence for a role of RAAS activation in the pathophysiology of AF and point to a potential role for stratification of therapeutic approaches by ACE genotype.

Prevención de la fibrilación auricular en el paciente hipertenso

A large percentage of patients with hypertension suffer from atrial fibrillation (AF). The presence of hypertension increases the risk of AF, which in turn aggravates hypertension. The ability of drugs to interfere with specific signal transduction pathways easing the presence of AF in hypertensive patients is promising. To date, the most effective mechanism appears to be the inhibition of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin-II receptor blockers (ARBs). This approach is under active investigation. Several trials have assessed the effectiveness of these drugs in the prevention of AF. Data show that both, ACEIs and ARBs, appear effective to prevent AF. However, a lack of prospective randomized double-blind trials data limits their application in absence of any other indication.

Prevalence of Paroxysmal Atrial Fibrillation Depending on the Regression of Left Ventricular Hypertrophy in Arterial Hypertension

Arterial hypertension (HTN) represents one of the major causes of atrial fibrillation, a cardiac arrhythmia with high prevalence and comorbidity. The aim of this study was to investigate whether paroxysmal atrial fibrillation can be treated by the regression of left ventricular hypertrophy achieved by antihypertensive therapy. Included in the present study were 104 patients who had had HTN for more than 1 year. None of them suffered from coronary heart disease. All patients were investigated by 24-h Holter ECG and echocardiography at baseline and after a mean of 24 months. Patients were divided into two groups: group A consisted of those (53.8%) who showed a regression of the left ventricular muscle mass index (LVMMI) during the follow-up (154.9+/-5.1 vs. 123.5+/-2.8 g/m(2)), and group B those (45.2%) who showed a progression of LVMMI (122.2+/-3.2 vs. 143.2+/-3.2 g/m(2)). In group A the prevalence of atrial fibrillation decreased from 12.5% to 1.8% (p<0.05), while it was increased in group B from 8.5% to 17.0%. The left atrial diameter was reduced following antihypertensive therapy in group A from 39.1+/-5.3 mm to 37.4+/-4.6 mm (p<0.01) and increased in group B from 37.0+/-0.7 mm to 39.0+/-0.9 mm (p<0.01). We conclude that a regression of the left ventricular muscle mass leads to a reduction of left atrial diameter and consecutively to a decrease in the prevalence of intermittent atrial fibrillation. This may be explained by a better left ventricular diastolic function following decreased vascular and extravascular resistance of the coronary arteries. This relation shows the benefits of causal antihypertensive therapy for the treatment of paroxysmal atrial fibrillation.

Upstream Therapy for Atrial Fibrillation

There are multiple factors for the etiology of atrial fibrillation (AF), including stretch, autonomic imbalance, hyperthyroidism, and inflammation. Of these factors for AF, stretch and inflammation increase the angiotensin II level, thereby inducing calcium over load, and inducing ectopic focal activities that initiate AF. Angiotensin II activates the Erk cascade through the AT(1)R and induces interstitial fibrosis of the atria, which compromises intra-atrial conduction. Short atrial refractoriness and slow conduction form multiple re-entry, before maintaining AF. Anti-arrhythmic drugs used for downstream therapy can suppress the focal activities and re-entry, but cannot prevent the development of a structural substrate. In contrast, angiotensin-converting enzyme, angiotensin II type 1 receptor blocker and statins might constitute upstream therapy through the prevention of structural remodeling that promotes AF.

Prevention of new-onset atrial fibrillation and its predictors with angiotensin II-receptor blockers in the treatment of hypertension and heart failure

Atrial fibrillation is the most frequent occurring sustained cardiac arrhythmia and it is related to common cardiac disease conditions. Hypertension increases the risk of atrial fibrillation by approximately two-fold and, because of the high prevalence of hypertension, it accounts for more cases of atrial fibrillation than any other risk factor. In recent years, there are two large hypertension trials (LIFE and VALUE) and two large heart failure trials (CHARM and Val-HeFT) reporting the beneficial effect of angiotensin II-receptor blockers (ARBs) on new-onset atrial fibrillation, beyond the blood pressure-lowering effect. Blockade of the renin-angiotensin system may prevent left atrial dilatation, atrial fibrosis, dysfunction and conduction velocity slowing. Some studies also indicate direct anti-arrhythmic properties. This review aims to consider the preventive effect of ARBs on new-onset atrial fibrillation observed in recent reports from these trials, and to discuss possible mechanisms of the beneficial effect of angiotensin II-receptor blockade.

Angiotensin II Antagonist in Paroxysmal Atrial Fibrillation (ANTIPAF) Trial

BACKGROUND AND OBJECTIVE

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Recent experimental data and retrospective analyses of clinical trials suggest that increased levels of angiotensin II can induce an arrhythmogenic atrial substrate, which favours the occurrence of AF. The purpose of the ANTIPAF (Angiotensin II Antagonist in Paroxysmal Atrial Fibrillation) trial is to prove the principal concept that blockade of angiotensin II type 1 receptors with olmesartan medoxomil 40 mg/day suppresses paroxysmal AF episodes during a 12-month follow-up. The ANTIPAF trial is the first placebo-controlled trial analysing the occurrence of AF as the primary study endpoint.

METHODS

Examination of the study hypothesis in a prospective, randomised, placebo-controlled, double-blind group comparison in patients with documented paroxysmal AF (total of 422 patients) stratified by beta-adrenoceptor antagonist use. The primary endpoint of the study is the percentage of days with documented episodes of paroxysmal AF identified on daily transtelephonic tele-ECG recordings. Patients will record and transmit at least one 1-minute ECG per day independent of symptoms. Furthermore, tele-ECG recordings will be transmitted in any case of symptomatic AF. The present paper summarises the rationale and design of the ANTIPAF trial.

[Therapeutic success of a prospective cardioversion protocol for persistent atrial fibrillation]

INTRODUCTION AND OBJECTIVES

The best therapeutic approach for persistent atrial fibrillation has yet to be defined. Our aim was to investigate the effects of cardioversion in unselected patients with persistent atrial fibrillation who were treated according to a strict protocol involving pretreatment, cardioversion, and follow-up.

METHODS

Consecutive patients with persistent atrial fibrillation of at least 1 months' duration were included prospectively in a cardioversion protocol that involved standard antiarrhythmic pretreatment, with amiodarone being offered first, and follow-up.

RESULTS

The study included 295 patients, 87.5% of whom were taking the antiarrhythmic drug amiodarone. Sinus rhythm was restored in 92.5%, with pharmacologic cardioversion occurring in 9.5%. The recurrence rate was 33.5% in the first month and 54.9% by month 12. Antiarrhythmic treatment had to be modified in 10.8% of patients. Independent risk factors for recurrence during the first year after cardioversion were an atrial fibrillation duration greater than one year, previous cardioversion, and left ventricular dilatation. A simple risk scoring system was able to differentiate between subgroups of patients with a low, intermediate or high risk of recurrence in the first year after cardioversion.

CONCLUSIONS

Sinus rhythm was maintained for 1 year after effective cardioversion in 45.1% of patients who received homogeneous antiarrhythmic pretreatment. There were few side effects. Recurrence can be predicted using clinical variables such as left ventricular dilatation, arrhythmia duration, and previous cardioversion.

Raised Plasma Aldosterone and Natriuretic Peptides in Atrial Fibrillation

BACKGROUND AND AIMS

During atrial fibrillation (AF), the renin-angiotensin-aldosterone system (RAAS) may be activated. In this study, our aim was to evaluate at a long-term follow-up visit the levels of plasma aldosterone and natriuretic peptides as markers of neurohormonal remodeling in patients with earlier, documented AF in relation to present heart rhythm, clinical data, and the left ventricular ejection fraction (LVEF). We hypothesized that increased levels of aldosterone and natriuretic peptides were significantly associated with present AF as markers of RAAS activation during the arrhythmia.

METHODS

We studied 158 patients with earlier ECG-documented AF followed by restored sinus rhythm (SR) attending a follow-up visit 2.6 years (mean) after primary inclusion.

RESULTS

At follow-up, 93 patients had SR. Heart rhythm at follow-up visit (SR/AF), plasma aldosterone, plasma N-terminal pro Brain Natriuretic Peptide (Nt-proBNP), plasma N-terminal pro Atrial Natriuretic Peptide (Nt-proANP), LVEF, medication, and clinical characteristics were recorded. Standard linear multiple regression analysis including age, sex, weight, hypertension, congestive heart failure, ischemic heart disease, present AF at follow-up, total duration of AF disease, ongoing medication, and the LVEF as explanatory variables showed that only ongoing treatment with diuretics was significantly associated (likelihood ratio test, p = 0.0057) with a raised log-transformed plasma aldosterone, although present AF at follow-up was related to a high aldosterone level (p = 0.09). For the natriuretic peptides, present AF at follow-up (p < 0.0001), age (p < 0.0001), female gender (p = 0.0047), ischemic heart disease (p = 0.0154), and ongoing treatment with sotalol (p = 0.0003) were all independently associated with high log-transformed plasma Nt-proANP. Likewise, present AF at follow-up (p = 0.0008) as well as age (p < 0.0001) were associated with high log-transformed plasma Nt-proBNP.

CONCLUSIONS

In patients with earlier AF, AF at long-term follow-up visit was independently associated with raised levels of Nt-proANP and Nt-proBNP and to some extent with plasma aldosterone indicating neurohormonal activation during arrhythmia.

[Atrial fibrillation]

Atrial fibrillation represents the arrhythmia that most frequently leads to hospital admission. Due to the age structure of our population and the increasing morbidity and comorbidity, one has to assume that this arrhythmia will reach an even higher prevalence. The therapeutic successes are often insufficient. First of all, it is important to diagnose and treat the underlying disease. Secondly, antiarrhythmic therapy has to be considered in symptomatic patients. In those patients and in the case of a persistent form, electrical cardioversion should be performed. Repetitive cardioversions in asymptomatic patients yield no advantage for mortality. Antiarrhythmic therapy consists of drugs of the classes Ia, Ic, and III. Concomitant anticoagulation is necessary; ASS in indicated only in patients without structural heart disease and lacking thromboembolic risk factors. If risk factors are present, effective therapy with coumarin derivatives is required. Therapy with ACE inhibitors and AT blockers leads to an advantage in patients with arterial hypertension and/or heart failure concerning the stability of sinus rhythm after cardioversion and the incidence of arrhythmia. Newer medications for anticoagulation and newer antiarrhythmic drugs raise the hope of a future therapy with higher efficacy and lower rate of side effects.

The Future of Atrial Fibrillation Therapy

Today management of atrial fibrillation (AF) centers on restoration and maintenance of normal sinus rhythm or control of the ventricular rate response to AF. Current guidelines state that rhythm and rate control strategies should be considered therapeutically equivalent, but recognize that no "one size fits all," an approach consistent with growing recognition of the heterogeneity of AF. As data from the Sotalol Amiodarone Atrial Fibrillation Efficacy Trial clearly demonstrate, conventional antiarrhythmics have a role in highly symptomatic AF accompanied by decreased quality of life. However, for many AF patients such drugs lack efficacy, have potentially serious side effects, and are poorly tolerated. In parallel with the development of more effective and safer antiarrhythmics, nontraditional approaches to prevention and treatment of AF are being explored. Treatments not considered "antiarrhythmic" that may prevent or forestall AF include aggressive antihypertensive therapy with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, and some, but not all, beta-blockers and calcium channel antagonists, especially when used as adjunctive therapy. Other approaches include statins, steroids, and fish oil to reduce atrial fibrosis and inflammation, and pacemakers to prevent bradycardia-mediated AF and as a pacing preventive strategy in selected patients. Ablative techniques with potential to cure AF are gaining popularity, but are not yet simple, straightforward, and risk-free procedures. In the future, treatment of AF will progress beyond today's focus on AF as a purely electrocardiographic disease toward a patient and context-specific management strategy involving multiple treatment modalities.

Future directions in antiarrhythmic drug therapy for atrial fibrillation

Atrial fibrillation is the most commonly sustained cardiac arrhythmia. Drugs currently approved by the US FDA for the treatment of this arrhythmia are imperfect owing to either side effects or limited efficacy. Drug development strategies have focused on two areas: the modification of existing agents – such as Class III drugs aimed at improving their safety and efficacy profile – and targeting newly postulated mechanisms of atrial fibrillation. In this article, we review new drugs currently in development and promising drug strategies for atrial fibrillation prevention and treatment.

The Renin-Angiotensin System: A Therapeutic Target in Atrial Fibrillation

There is growing evidence to suggest a role for the renin-angiotensin system (RAS) in the pathogenesis of atrial fibrillation (AF). Experimental animal data suggest RAS-dependent mechanisms for the development of a structural and electrophysiologic substrate for AF. This is consistent with clinical data demonstrating the effectiveness of RAS blockade in preventing new-onset or recurrent AF in a variety of patient populations including patients with hypertension and left ventricular hypertrophy, congestive heart failure, and those undergoing electrical cardioversion for AF. This review summarizes experimental and clinical evidence to date relating to the role of RAS in the pathogenesis of AF, and the efficacy of its inhibition in managing this common arrhythmia.

Use of beta-blockers, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers to prevent atrial fibrillation

Atrial fibrillation, the most common cardiac arrhythmia in clinical practice, causes significant burden to patients and health care systems worldwide. Attention is being paid to prevention of atrial fibrillation using drugs that retard or prevent atrial fibrosis and arrhythmogenic remodeling, which lead to this arrhythmia. Agents that work through the renin-angiotensin-receptor system, the angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, are showing promise in animal and human studies.

Medical Management of Atrial Fibrillation: State of the Art

Predominantly a disease of advancing age, atrial fibrillation (AF) is the most common sustained arrhythmia. Its prevalence is rising as the proportion of elderly people in the population continues its inexorable rise. Without more effective therapeutic interventions, AF-related cardiovascular and cerebrovascular morbidity and mortality will also continue to rise. Antiarrhythmic drugs are an essential tool in the management of AF and may be used as premedication before cardioversion; together with cardioversion to help or assist cardioversion; or given afterward to prevent recurrence. If AF recurs after one or two cardioversions, then it is usual to adopt a rate control strategy; highly symptomatic patients who fail cardioversion may benefit from ablation therapy. We are already on the threshold of a large expansion in the use of ablation therapy, a strategy that has potential to deliver dramatic improvements in outcome. Not only can AF be cured by ablative therapy, but there is also evidence that it confers functional improvement as well. It will not, however, be appropriate for all AF patients and pharmacological therapies will continue to have an important place in the management of AF. The plethora of antiarrhythmic drugs currently available for the treatment of AF is a reflection that none is wholly satisfactory, each having limited efficacy combined with poor safety and tolerability. Improved class III antiarrhythmic agents, such as dronedarone; new classes of antiarrhythmic agents, such as atrial repolarization delaying agents; and upstream therapies dealing with substrate represent potential sources of new pharmacological therapies for AF.

Amiodarone: A multifaceted antiarrhythmic drug

Synthesized as an antianginal compound 40 years ago, amiodarone has emerged as a uniquely effective antiarrhythmic compound in recent years. It has numerous properties, the most prominent being the ability to lengthen repolarization in the atria and ventricles associated with bradycardia without the significant potential for torsades de pointes. Amiodarone effectively controls a wide spectrum of atrial and ventricular antiarrhythmic disorders, but its limiting side effects, such as thyroid dysfunction, pulmonary fibrosis, and dermatologic changes, may limit its long-term use in some patients. What aspects of the multiplicity of the properties of amiodarone are relevant to its unusual efficacy is not known. Deiodination and other structural changes in the amiodarone molecule have has led to a the loss of thyroid and pulmonary effects in the resulting derivative, dronedarone, which is in advanced clinical development.

Atrial fibrillation: Choosing an antiarrhythmic drug

Atrial fibrillation is the most common arrhythmia encountered in clinical practice. The associated hemodynamic changes can lead to symptoms of palpitations, fatigue, light-headedness, or dyspnea. Extensive research in the use of antiarrhythmic drugs has been performed both to facilitate the conversion of atrial fibrillation to sinus rhythm and to maintain normal sinus rhythm. The relative merits of a rhythm control versus rate control strategy are briefly discussed. Efficacy of the available agents for pharmacologic cardioversion is reviewed in detail. Important drugs for maintenance of sinus rhythm include amiodarone, flecainide, propafenone, sotalol, and dofetilide. Selection of the appropriate antiarrhythmic drug must be individualized to the clinical situation, with Class IC drugs being first-line agents in the absence of structural heart disease. Regardless of agent selected, appropriate monitoring for development of adverse effects is of utmost importance.

Efficacy of Angiotensin Receptor Blockers in Cardiovascular Disease

The cardiovascular continuum describes the progression of pathophysiologic events from cardiovascular risk factors to symptomatic cardiovascular disease (CVD) and life-threatening events. Pharmacologic intervention early in the continuum may prevent or slow CVD development and improve quality of life. The renin-angiotensin-aldosterone system (RAAS) is central to the pathophysiology of CVD at many stages of the continuum. Numerous clinical trials of angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) have shown that RAAS blockade provides benefits to patients across the continuum. ARBs are as effective as ACE inhibitors in the treatment of hypertension; however tolerability and adherence to therapy appear to be improved with ARBs. Large clinical trials have shown that ARBs may provide therapeutic benefits beyond blood pressure control in patients with diabetes, heart failure or at risk of heart failure following a myocardial infarction. In addition, ARBs have been shown to provide protective effects in patients with impaired renal function or left ventricular hypertrophy. Additional clinical trials are ongoing to further characterize the role of ARBs in CVD management.

Atrial Fibrillation Burden During the Post-Implant Period After CRT Using Device-Based Diagnostics

AF Burden After CRT Implantation.

AIMS

Cardiac resynchronization therapy (CRT) is increasingly used in congestive heart failure (CHF) patients (with cardiac dyssynchrony). In addition to delivering therapy, CRT devices offer a variety of diagnostic tools for continuous long-term monitoring of clinically relevant information (i.e., occurrence and duration of arrhythmia episodes).

METHODS AND RESULTS

Eighty-four patients with drug-refractory CHF in NYHA-class II-IV received a CRT device. The response to CRT was assessed by determining NYHA class at baseline and at 3 months follow-up. Atrial fibrillation (AF) burden (defined as time of AF per day) was continuously measured by the device. A significant gradual reduction of AF burden (from 9.88 +/- 12.61 to 4.20 +/- 9.24 [hours/day]) and number of patients experiencing AF episodes (from 26 to 13) were observed during CRT.

CONCLUSIONS

(1) Diagnostic features for long-term monitoring of physiological variables provide useful information on the state and course of AF and may improve disease management. (2) AF burden reduces over time during the first 3 months after CRT implantation.

The Bachmann Bundle and interatrial conduction

The cardiac conduction system (CCS) is responsible for generation and systematic conduction of cardiac impulses. The Bachmann Bundle (BB), considered one of its several accessory impulse-conducting pathways, plays a fundamental role in interatrial conduction. Delay in this pathway leads to prolongation of the P wave on the electrocardiogram (interatrial delay or block), which in turn is a precursor for atrial tachyarrhythmias, mainly atrial fibrillation and significant left atrial electromechanical dysfunction. As such, the magnitude of its sequelae has necessitated a flurry of investigations that have been targeted toward its prevention and management. Although current studies on the use of angiotensin-converting enzyme inhibitors and atrial pacing have indeed shown some promise, it would be shortsighted to overlook and circumvent the actual underlying lesion-BB abnormality. Thus, a thorough understanding of the CCS and interatrial conduction is essential. We review current literature on the BB and discuss potential mechanisms that affect its conduction.

The management of atrial fibrillation in heart failure

The development of atrial fibrillation (AF) can greatly complicate the course of heart failure (HF). Although recent trials have indicated the nonsuperiority of a rhythm control strategy in the general population with AF, this may not apply to patients with HF. We feel strongly that AF be treated aggressively in patients with HF, defaulting toward an initial rhythm control strategy, to avoid the hemodynamic detriment of irregular rapid ventricular response and the development of tachycardia-related myopathy. The index episode is treated with cardioversion and antiarrhythmic therapy. If significant benefit is demonstrated, the rhythm control strategy is maintained, to the point of catheter ablation for AF if necessary. If there is no change in cardiac performance or symptoms after cardioversion, strict rate control is enforced, to the point of atrioventricular node ablation and pacing if necessary.

Clinical trials, the renin angiotensin system and atrial fibrillation

PURPOSE OF REVIEW

Atrial fibrillation is the most common clinical arrhythmia. Current treatment strategies are far from optimal. One new research direction is to target the atrial fibrillation substrate and to examine whether drugs can produce atrial structural and/or electrophysiological remodeling and whether this results in a reduction in atrial fibrillation burden.

RECENT FINDINGS

Two prospective randomized studies have shown that the addition of an angiotensin converting enzyme inhibitor or an angiotensin receptor blocker to amiodarone reduces the recurrence rate of atrial fibrillation after electrical cardioversion. There are ten completed prospective clinical trials with atrial fibrillation as a secondary endpoint or assessed in post-hoc analysis. Five of these studies have reported a positive impact of angiotensin converting enzyme inhibitors or angiotensin receptor blockers on atrial fibrillation burden. A meta-analysis showed that active drugs reduced the overall risk of development of atrial fibrillation by 28%. Patients in the heart failure trials obtained most benefit from these drugs (relative risk reduction 44%, P = 0.07).

SUMMARY

The initial basic science and clinical trial data suggest that modulation of the renin angiotensin system may be an effective treatment for atrial fibrillation. The following, however, remain to be clarified: do these drugs have a clinically meaningful impact on atrial fibrillation burden; if there is an impact, is it similar in all atrial fibrillation patients or just in certain subsets; do angiotensin converting enzyme inhibitors and angiotensin receptor blockers have similar benefits; and is there a role for aldosterone antagonists?

Fibrosis in heart disease: understanding the role of transforming growth factor-beta in cardiomyopathy, valvular disease and arrhythmia

The importance of fibrosis in organ pathology and dysfunction appears to be increasingly relevant to a variety of distinct diseases. In particular, a number of different cardiac pathologies seem to be caused by a common fibrotic process. Within the heart, this fibrosis is thought to be partially mediated by transforming growth factor-beta1 (TGF-beta1), a potent stimulator of collagen-producing cardiac fibroblasts. Previously, TGF-beta1 had been implicated solely as a modulator of the myocardial remodelling seen after infarction. However, recent studies indicate that dilated, ischaemic and hypertrophic cardiomyopathies are all associated with raised levels of TGF-beta1. In fact, the pathogenic effects of TGF-beta1 have now been suggested to play a major role in valvular disease and arrhythmia, particularly atrial fibrillation. Thus far, medical therapy targeting TGF-beta1 has shown promise in a multitude of heart diseases. These therapies provide great hope, not only for treatment of symptoms but also for prevention of cardiac pathology as well. As is stated in the introduction, most reviews have focused on the effects of cytokines in remodelling after myocardial infarction. This article attempts to underline the significance of TGF-beta1 not only in the post-ischaemic setting, but also in dilated and hypertrophic cardiomyopathies, valvular diseases and arrhythmias (focusing on atrial fibrillation). It also aims to show that TGF-beta1 is an appropriate target for therapy in a variety of cardiovascular diseases.

Drug Insight: angiotensin-converting-enzyme inhibitors and atrial fibrillation--indications and contraindications

Large clinical trials have demonstrated that angiotensin-converting-enzyme (ACE) inhibitors are associated with beneficial outcomes in patients with arterial hypertension, heart failure, coronary artery disease, or a combination of these conditions. Other reports have suggested that ACE inhibitors prevent the development or recurrence of atrial fibrillation (AF), a common arrhythmia. In the TRACE trial, in patients with reduced left ventricular function after myocardial infarction, trandolapril reduced the frequency of AF. In the SOLVD trial, a 78% reduction in the frequency of AF after infarction was noted with enalapril compared with placebo. Studies in patients with persistent AF undergoing cardioversion suggest that ACE inhibitors improve outcomes and prevent AF recurrences. The mechanism of AF prevention by ACE inhibitors is unclear, but experimental data show prevention or attenuation of pacing-induced atrial remodeling with ACE inhibitor use. ACE inhibitors decrease angiotensin II concentration; angiotension II stimulates mitogen-activated protein kinases, which in turn activate fibrosis formation and lead to conduction heterogeneity and induction of AF. On the other hand, AF induces atrial dilatation, atrial stretch and atrial secretion of ACE. Among other properties, ACE inhibitors have a sympatholytic effect and increase baroreceptor sensitivity. This review discusses the current data on the use of ACE inhibitors for AF prevention. Although these drugs represent a promising therapeutic option for AF patients, the data so far seem only supportive rather than definitive. Prospective trials are required to validate the benefit of ACE inhibitors and to investigate which patients are most likely to benefit from this pharmacological therapy.

Rationale and design of the GISSI-Atrial Fibrillation Trial: a randomized, prospective, multicentre study on the use of valsartan, an angiotensin II AT1-receptor blocker, in the prevention of atrial fibrillation recurrence

BACKGROUND

The possibility of preventing atrial fibrillation recurrence with anti-arrhythmic agents is very limited, given the discouraging results obtained with current drugs in many patients. Data from experimental studies suggest that angiotensin II AT1-receptor blockers can influence atrial remodelling, a key factor in atrial fibrillation initiation and maintenance. Moreover, some preliminary clinical data show that angiotensin II AT1 -receptor blockers can prevent atrial fibrillation episodes. The GISSI-Atrial Fibrillation (AF) trial is a randomized, prospective, parallel group, placebo-controlled, multicentre study designed to test whether angiotensin II AT1-receptor blockers can reduce atrial fibrillation recurrence.

OBJECTIVES AND METHODS

The primary objective of the study is to demonstrate that, in patients with a history of recent atrial fibrillation who are treated with the best recommended therapies, the addition of the angiotensin II AT1-receptor blocker valsartan (titrated up to 320 mg) is superior to placebo in reducing atrial fibrillation recurrence. A substudy will analyse the effect of valsartan on left atrial dimensions and on neurohormones. The study population consists of patients with symptomatic atrial fibrillation (at least two electrocardiogram documented atrial fibrillation episodes in the previous 6 months or successful cardioversion in the last 2 weeks) with underlying cardiovascular diseases or comorbidities. With approximately 100 centres participating in Italy, a total of 1402 patients are randomized in a 1 : 1 ratio to receive valsartan or placebo. The enrolment period will last 12 months and the patients will be followed for 12 months from study entry.

CONCLUSIONS

The GISSI-AF is the largest trial aimed at assessing the role of angiotensin receptor blockade in reducing the recurrence of atrial fibrillation and its possible mechanisms of action in terms of its effects on atrium remodelling and neurohormones.

Atrial fibrillation in patients hospitalized for congestive heart failure: The same prognostic influence independently of left ventricular systolic function?

Atrial fibrillation (AF) was described to be associated with an adverse prognosis in several studies of heart failure (HF). However, it is not clear whether it directly increased mortality or is only a marker for severity of HF.

AIMS

To determine the influence of AF on mortality of HF patients distinguishing between patients with preserved and deteriorated systolic function (SF).

METHOD AND RESULTS

1636 patients who, between 1991 and 2002 had been hospitalized in a Cardiology Service for HF, were studied. Survival (SV) data (mean follow-up time: 3.14 years) has shown that there was no difference in SV between patients with (540 patients of the whole group) and without AF in the group with preserved SF (presented in 38.7% of cases), however, in the group of patients with deteriorated SF (AF presented in 31.0% of cases), SV time was significantly (p=0.01) shorter among patients with AF, this association being independent of age, sex, aetiology, risk factors, clinical signs and pharmacological treatment; relative risk: 1.831(1.120-2.994).

CONCLUSION

AF is more prevalent among HF patients with preserved SF than among those with deteriorated SF, but only increases the risk of death among the latter.

[New antiarrhythmic drugs for therapy of atrial fibrillation: II. Non-ion channel blockers]

The therapeutic approach to atrial fibrillation is difficult and challenging. The effect of "classical" antiarrhythmic agents is based on their inhibitory effects on various ion channels. However, therapeutic benefit of these agents is often limited. The primary goal of this article is to discuss new therapeutic approaches using non-ion channel blocking drugs in the treatment of atrial fibrillation. Some of the substances discussed in this article have been used already in the clinical practice. Others, for example gentherapeutic approaches, are still in the experimental state. In contrast to ion channel blocking agents their efficacy is based on the suppression of structural remodeling. Hence, it can be assumed that due to these effects they may also be beneficial in the primary prevention of atrial fibrillation.

Prevention of atrial fibrillation in patients with symptomatic chronic heart failure by candesartan in the Candesartan in Heart failure: assessment of Reduction in Mortality and morbidity (CHARM) program

BACKGROUND

Atrial fibrillation (AF) is frequent in patients with chronic heart failure (CHF). Experimental and small patient studies have demonstrated that blocking the renin-angiotensin-aldosterone system may prevent AF. In the CHARM program, the effects of the angiotensin receptor blocker candesartan on cardiovascular mortality and morbidity were evaluated in a broad spectrum of patients with symptomatic CHF. CHARM provided the opportunity to prospectively determine the effect of candesartan on the incidence of new AF in this CHF population.

METHODS

7601 patients with symptomatic CHF and reduced or preserved left ventricular systolic function were randomized to candesartan (target dose 32 mg once daily, mean dose 24 mg) or placebo in the 3 component trials of CHARM. The major outcomes were cardiovascular death or CHF hospitalization and all-cause mortality. The incidence of new AF was a prespecified secondary outcome. Median follow-up was 37.7 months. A conditional logistic regression model for stratified data was used.

RESULTS

6446 patients (84.8%) did not have AF on their baseline electrocardiogram. Of these, 392 (6.08%) developed AF during follow-up, 177 (5.55%) in the candesartan group and 215 (6.74%) in the placebo group (odds ratio 0.812, 95% CI 0.662-0.998, P = .048). After adjustment for baseline covariates, the odds ratio was 0.802 (95% CI 0.650-0.990, P = .039). There was no heterogeneity of the effects of candesartan in preventing AF between the 3 component trials (P = .57).

CONCLUSIONS

Treatment with the angiotensin receptor blocker candesartan reduced the incidence of AF in a large, broadly-based, population of patients with symptomatic CHF.

Angiotensin II potentiates the slow component of delayed rectifier K+ current via the AT1 receptor in guinea pig atrial myocytes

BACKGROUND

Angiotensin II (Ang II) has diverse actions on cardiac electrical activity. Little information is available, however, regarding immediate electrophysiological effects of Ang II on cardiac repolarization.

METHODS AND RESULTS

The present study investigated the immediate effects of Ang II on the slow component of delayed rectifier K+ current (IKs) and action potentials in guinea pig atrial myocytes using the whole-cell patch-clamp technique. Bath application of Ang II increased the amplitude of IKs (EC50, 6.16 nmol/L) concentration dependently. The stable analogue Sar1-Ang II was also effective at increasing IKs. The voltage dependence of IKs activation and the kinetics of deactivation were not significantly affected by these agonists. The enhancement of IKs was blocked by the Ang II type 1 (AT1) receptor antagonist valsartan (1 micromol/L) and was markedly attenuated by inclusion of GDPbetaS (2 mmol/L) in the pipette, indicating an involvement of G protein-coupled AT(1) receptor. The stimulatory effect was also significantly reduced by the phospholipase C inhibitor compound 48/80 (100 micromol/L) and the protein kinase C inhibitors bisindolylmaleimide I (200 nmol/L) and H-7 (10 micromol/L), suggesting that AT1 receptor acts through phospholipase C-protein kinase C signaling cascade to potentiate I(Ks). As expected from its stimulatory action on IKs, Sar1-Ang II markedly shortened the action potential duration, which could be reversed by valsartan.

CONCLUSIONS

The potentiation of IKs via AT1 stimulation in atrial myocytes, accompanied by a shortening of the action potential duration, suggests a potential mechanism by which elevated levels of Ang II may promote atrial fibrillation in heart failure and warrants further investigation.

Hypertension treatment and implications of recent cardiovascular outcome trials

Clinical trials have shown that effective control of blood pressure reduces the risk of cardiovascular events in high-risk patients. For example, data from the Valsartan Antihypertensive Long-term Use Evaluation (VALUE) study show significant reductions in the incidence of cardiac events, stroke and all-cause mortality in patients in whom blood pressure control was achieved compared with those in whom blood pressure remained uncontrolled. Although the Antihypertensive and Lipid-Lowering treatment to prevent Heart Attack Trial (ALLHAT) demonstrated no significant difference in cardiovascular mortality and morbidity between patients receiving diuretics, calcium channel blockers or angiotensin-converting enzyme (ACE) inhibitors, this finding might have been confounded by differences in the blood pressure reductions achieved with the three treatments. Other studies have consistently shown that newer antihypertensive agents, such as ACE inhibitors and calcium channel blockers, reduce cardiovascular events to a similar, or possibly greater, extent as older therapies, such as diuretics and beta-blockers. In particular, ACE inhibitors appear to offer additional benefits beyond blood pressure reduction in terms of reducing cardiovascular events and producing renoprotective effects. Angiotensin II receptor blockers (ARBs) have been less extensively studied, but there is evidence already that they have heart failure, stroke and renoprotective benefits. The ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET) is currently comparing the effects of the ARB telmisartan 80 mg and the ACE inhibitor ramipril 10 mg, alone and in combination, on cardiovascular events in high-risk patients.

The pleiotropic effects of angiotensin receptor blockers

The angiotensin receptor blockers (ARBs) are very effective and safe antihypertensive drugs. They exert their antihypertensive effect through blockage of the angiotensin II, type 1 receptor and quite possibly through stimulation by angiotensin II of the unoccupied type 2 receptor. Besides hypertension, the ARBs have been found recently to be of value in the treatment of heart failure and diabetic nephropathy. In addition, ARBs have emerged lately as being very effective and perhaps superior to other antihypertensive drugs in the prevention of de novo or recurrent strokes. Other actions that may account for their stroke-protective effects include their antiatherogenic, antidiabetic, antiplatelet aggregating, hypouricemic, and atrial antifibrillatory actions. All these actions make the ARBs a true pleiotropic class of drugs. Each of the foregoing effects will be discussed briefly in this concise review.