Amiodarone versus sotalol for atrial fibrillation

Verapamil versus digoxin and acute versus routine serial cardioversion for the improvement of rhythm control for persistent atrial fibrillation

OBJECTIVES

The VERDICT (Verapamil Versus Digoxin and Acute Versus Routine Serial Cardioversion Trial) is a prospective, randomized study to investigate whether: 1) acutely repeated serial electrical cardioversions (ECVs) after a relapse of atrial fibrillation (AF); and 2) prevention of intracellular calcium overload by verapamil, decrease intractability of AF.

BACKGROUND

Rhythm control is desirable in patients suffering from symptomatic AF.

METHODS

A total of 144 patients with persistent AF were included. Seventy-four (51%) patients were randomized to the acute (within 24 h) and 70 (49%) patients to the routine serial ECVs, and 74 (51%) patients to verapamil and 70 (49%) patients to digoxin for rate control before ECV and continued during follow-up (2 x 2 factorial design). Class III antiarrhythmic drugs were used after a relapse of AF. Follow-up was 18 months.

RESULTS

At baseline, there were no significant differences between the groups, except for beta-blocker use in the verapamil versus digoxin group (38% vs. 60%, respectively, p = 0.01). At follow-up, no difference in the occurrence of permanent AF between the acute and the routine cardioversion groups was observed (32% [95% confidence intervals (CI)] 22 to 44) vs. 31% [95% CI 21 to 44], respectively, p = NS), and also no difference between the verapamil- and the digoxin-randomized patients (28% [95% CI 19 to 40] vs. 36% [95% CI 25 to 48] respectively, p = NS). Multivariate Cox regression analysis revealed that lone digoxin use was the only significant predictor of failure of rhythm control treatment (hazard ratio 2.2 [95% CI 1.1 to 4.4], p = 0.02).

CONCLUSIONS

An acute serial cardioversion strategy does not improve long-term rhythm control in comparison with a routine serial cardioversion strategy. Furthermore, verapamil has no beneficial effect in a serial cardioversion strategy.

Quality of Life and Exercise Performance in Patients in Sinus Rhythm Versus Persistent Atrial Fibrillation

OBJECTIVES

The purpose of this study was to determine quality of life (QOL) and exercise performance (EP) in patients with persistent atrial fibrillation (AF) converted to sinus rhythm (SR) compared with those remaining in or reverting to AF.

BACKGROUND

Restoration of SR in patients with AF improving QOL and EP remains controversial.

METHODS

Patients with persistent AF were randomized double-blind to amiodarone, sotalol, or placebo. Those not achieving SR at day 28 were cardioverted and classified into SR or AF groups at 8 weeks (n = 624) and 1 year (n = 556). The QOL (SF-36), symptom checklist (SCL), specific activity scale (SAS), AF severity scale (AFSS), and EP were assessed.

RESULTS

Favorable changes were seen in SR patients at 8 weeks in physical functioning (p < 0.001), physical role limitations (p = 0.03), general health (p = 0.002), and vitality (p < 0.001), and at 1 year in general health (p = 0.007) and social functioning (p = 0.02). Changes in the scores for SCL severity (p = 0.01), functional capacity (p = 0.003), and AFSS symptom burden (p < 0.001) at 8 weeks and in SCL severity (p < 0.01) and AF symptom burden (p < 0.001) at 1 year showed significant improvements in SR versus AF. Symptomatic patients were more likely to have improvement. The EP in SR versus AF was greater from baseline to 8 weeks (p = 0.01) and to 1 year (p = 0.02). The EP correlated with physical functioning and functional capacity except in the AF group at 1 year.

CONCLUSIONS

In patients with persistent AF, restoration and maintenance of SR was associated with improvements in QOL measures and EP. There was a strong correlation between QOL measures and EP.

What are arrhythmogenic substrates in diabetic rat atria?

INTRODUCTION

Diabetes mellitus is one of the significant independent risk factors for the development of atrial fibrillation (AF). However, the pathophysiological mechanisms of the relationship have not been fully elucidated.

METHODS AND RESULTS

The genetic type II diabetes (GK) rats and their original (Wistar) ones were subjected to electrophysiological (n = 8 per group) and histological (n = 7 per group) studies. At 40 weeks old, when GK rats had significantly (P < 0.01) more increased plasma glucose and HbA(1c) values than Wistar rats, atrial electrical stimuli in the isolated-perfused hearts induced significantly greater number of repetitive atrial responses in GK rats than in Wistar rats (47.9 +/- 17.5 vs 3.1 +/- 1.3 beats, respectively, P < 0.01). GK rats showed significantly longer intra-atrial activation time than Wistar rats (18.3 +/- 0.4 ms vs 15.9 +/- 0.5 ms, P < 0.01) without any significant difference in the atrial refractoriness. The histological examination revealed significantly increased diffuse fibrotic deposition in GK rats atria compared with Wistar ones (P < 0.01).

CONCLUSION

The present diabetic GK rat showed increased atrial arrhythmogenicity with intra-atrial conduction disturbance, and thus indicated that the structural remodeling of atrium characterized by diffuse interstitial fibrosis would be a major substrate for diabetes-related AF.

Implication from randomized trials of rate and rhythm controls on management of patients with persistent atrial fibrillation

Recently, several randomized trials were published on the issue of rate or rhythm control for patients with atrial fibrillation (AF). Patients were typically minor symptomatic, relatively old, with age above 70, presenting with a recurrence of AF and suffering from only mild to moderate underlying heart disease. The main outcome of these trials is that rate control is not inferior to rhythm control for the management of patients with AF concerning morbidity and mortality. Also patients' quality of life did not differ significantly in follow-up in these trials. However, rhythm control is not redundant in the treatment of AF. Focus is now on subgroups of patients who could still have benefit being in sinus rhythm. For severely symptomatic patients, patients presenting with the first episode of AF and probably those with severe congestive heart failure, to restore and maintain sinus rhythm should still be the goal. With the failure of antiarrhythmic therapy, nonpharmacological approaches such as pulmonary vein isolation can be performed. Another finding of the randomized trials is that being in sinus rhythm does not prevent from the occurrence of thromboembolic complications. This means that for patients with AF, with risk factors for thromboembolic events, adequate anticoagulant therapy is indicated irrespective of the current heart rhythm. As with antiarrhythmic therapy, the search for new and safer anticoagulant therapy is underway. This review will focus on the key aspects we have learned from the randomized trials on rate and rhythm controls for patients with AF.

Pharmacologic approaches to rhythm versus rate control in atrial fibrillation—where are we now?

Until recently, contemporary drug treatment of atrial fibrillation (AF) focused primarily on restoration and maintenance of sinus rhythm, predicated on the belief that if AF is abolished then problems associated with AF would be abolished too. Recently completed clinical trials using drug therapy and comparing maintenance of sinus rhythm with control of ventricular rate have challenged this assumption, showing that simple control of ventricular rate with anticoagulation is an acceptable primary therapy, notably in older patients with persistent AF, minimally symptomatic or asymptomatic, and at increased risk for thromboembolic events. However, rate control and anticoagulation is not a panacea; existing trial results should not be interpreted to mean all patients should be treated with the rate control approach. Despite the limited efficacy and poor safety of current antiarrhythmic drugs, strategies for maintenance of sinus rhythm remain justified in many patients, such as those with first-episode AF, highly symptomatic patients, younger patients, and those with a history of congestive heart failure (CHF). Commonly used current and some investigational agents designated for "rhythm control" have enough pharmacologic overlap with rate control agents to be considered to have a dual mode of action, simultaneously addressing both rhythm and rate control. Furthermore, there is much interest in non-pharmacologic therapies, such as radiofrequency ablation, for rhythm control. The lack of appropriately designed and controlled trials at this time makes it difficult to determine the place of radiofrequency ablation and its impact on the rhythm versus rate question.

[Anticoagulation with atrial fibrillation]

Atrial fibrillation is associated with a relevant risk for ischemic stroke: Observational studies suggest that one in four to five strokes is due to atrial fibrillation. Depending on the risk profile of an individual patient, the yearly risk for a stroke is between 2% and 14%. Continuous oral anticoagulation is indicated if atrial fibrillation is accompanied by at least one additional risk factor for thromboembolic complications. This recommendation is supported by several large randomized trials. Due to their low therapeutic range, vitamin K antagonists (phenprocoumon, warfarin, and others), the most commonly used oral anticoagulants, require regular anticoagulation monitoring. If well-controlled (international normalized ratio 2-3, in elderly patients preferably 2-2.5), oral anticoagulation prevents more than half of ischemic strokes related to atrial fibrillation, while bleeding complications are rare. In the follow-up of low risk patients (CHADS2-Score 0), oral anticoagulation becomes necessary when risk factors for thromboembolic complications develop. If a stroke occurs during oral anticoagulation and an INR>2 in a patient with atrial fibrillation, other causes than thromboembolic events should be considered. New anticoagulants--especially direct thrombin antagonists--are currently evaluated in clinical trials and may in the future facilitate anticoagulation in patients with atrial fibrillation.

[Electrical and pharmacological strategies for early cardioversion of atrial fibrillation]

Cardioversion of atrial fibrillation as an element of rhythm control strategy is indicated in patients with first episode of atrial fibrillation, hemodynamic instability, recurrent atrial fibrillation with low probability of spontaneous conversion, or severe symptoms. Early cardioversion is performed within 48 h of onset of atrial fibrillation. The best point in time is still unknown. It can be performed by pharmacological, or, preferentially, by electrical cardioversion. The advantages of electrical cardioversion are higher efficacy and no proarrhythmic risk, however, short time general anaesthesia is needed. Electrical cardioversion is most effective when biphasic shocks are delivered. For pharmacological cardioversion, several antiarrhythmic drugs are available which have to be considered individually. Thromboembolic risk does not differ between the two methods. Early cardioversion and maintenance of sinus rhythm is most effective in atrial fibrillation of short duration, normal left atrial size and no or only mild structural heart disease.

Drug therapy for atrial fibrillation

Although the maintenance of sinus rhythm would be the ideal scenario for patients with atrial fibrillation (AF), recent randomised trials have questioned the value of this approach. A careful interpretation of their results showed the limited efficacy of currently available antiarrhythmic drugs in maintaining sinus rhythm, as well as their potentially serious side effects. Therefore, it is imperative to develop safer and more effective drugs for AF. Based on our improved understanding of the pathophysiology of AF and the mechanism of action of antiarrhythmic drugs, significant efforts are being made to develop new antiarrhythmic agents that would prevent electrophysiological remodelling, would be selective for the atria and, therefore, would not prolong ventricular repolarisation, thus lacking any proarrhythmic effect.

A randomized trial of prophylactic antiarrhythmic agents (amiodarone and sotalol) in patients with atrial fibrillation for whom direct current cardioversion is planned

Antiarrhythmic agents enhance maintenance of sinus rhythm (SR) after direct current cardioversion (DCC) for atrial fibrillation but there are few comparative trials.

BACKGROUND

The aims of the study were (1) to establish whether patients successfully cardioverted to SR are more likely to stay in SR over 6 months if taking amiodarone or sotalol, and if so, to establish whether one agent is better than the other; (2) to establish whether taking amiodarone or sotalol is better at achieving chemical cardioversion within the 6 weeks before DCC; and (3) to establish whether DCC is more likely to be successful on a drug.

METHODS

Randomized, prospective, nonblinded, controlled study of treatment with either amiodarone (n = 27), sotalol (n = 36), or no antiarrhythmic agent (n = 31).

RESULTS

Chemical cardioversion occurred in 7 patients in the amiodarone group (A), 7 patients in the sotalol group (S), but none in the no-antiarrhythmic group (N). A total of 33 (92%) patients in the sotalol group, 22 (81%) patients in the amiodarone group, and 23 (74%) patients in the no-antiarrhythmic group were in SR after cardioversion. Of the original cohort of patients, 17 (63%) patients in the amiodarone group remained in SR at 6-month follow-up, compared with 14 (39%) in the sotalol group and 5 (16%) in the no-antiarrhythmic group (A vs N, P < .0002, P < .0006B [after Bonferroni correction]; A vs S, P = .05, P = .15B; and S vs N, P = .03, P = .09B).

CONCLUSIONS

Amiodarone and sotalol achieved chemical cardioversion before planned electrical cardioversion in 26% and 19% of patients, respectively. After successful cardioversion, amiodarone appears better than sotalol at maintaining SR at 6 months.

Controversies in atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia, and contributes greatly to cardiovascular morbidity and mortality. Many aspects of the management of atrial fibrillation remain controversial. We address nine specific controversies in atrial fibrillation management, briefly focusing on the relations between mechanisms and therapy, the roles of rhythm and rate control, the definition of optimum rate control, the need for early cardioversion to prevent remodelling, the comparison of electrical with pharmacological cardioversion, the selection of patients for long-term oral anticoagulation, the roles of novel long-term anticoagulation approaches and ablation therapy, and the potential usefulness of upstream therapy targeting substrate development. The background of every controversy is reviewed and our opinions expressed. Here, we hope to inform physicians about the most important controversies in this specialty and stimulate investigators to address unresolved issues.

Pharmakotherapie der supraventrikulären Rhythmusstörungen

Supraventricular tachycardias consist of AV-nodal-reentrant-tachycardias, atrioventricular tachycardias with accessory pathways (WPW-syndrome), atrial tachycardias, atrial fibrillation and atrial flutter. Only specific ECG interpretation with an exact arrhythmia classification offers the way to perform modern differential therapy including drug treatment and also interventional therapy modalities. In atrial fibrillation, drug treatment is still first-line therapy: physicians have to make a decision either to follow the rate or rhythm control concept. In case of rhythm control, drug therapy is tailored to the individual patient taking into account the patients symptomatology, left ventricular ejection fraction and nature and degree of an underlying cardiac disease. Drug refractory symptomatic atrial fibrillation patients should be considered for interventional treatment like pulmonary vein ablation. Recurrent typical right atrial flutter, AV-nodal-reentrant-tachycardia and all forms of atrioventricular tachycardias however are indications for catheter ablation; long-term drug treatment will only be performed in rare cases.

Temas de actualidad 2005: electrofisiología y arritmias

Cardiac electrophysiology laboratories deal with a wide range of pathological conditions, diagnostic techniques, and treatments. Since a huge quantity of material has been published in recent months, this article will be limited to discussion of the most significant developments in the prognostic evaluation of arrhythmias, hereditary disease, syncope, atrial fibrillation, implantable cardioverter-defibrillators, cardiac resynchronization therapy, and catheter ablation. Even within these areas, discussion will be restricted to specific concrete topics and to a limited number of publications that were judged to have important implications for clinical practice. Our principal aim was to provide clinical cardiologists with an overview of the latest developments in cardiac electrophysiology.

Atrial Fibrillation and Congestive Heart Failure: Risk Factors, Mechanisms, and Treatment

Atrial fibrillation (AF) and congestive heart failure (CHF) are commonly encountered together, and either condition predisposes to the other. Risk factors for AF and CHF include age, hypertension, valve disease, and myocardial infarction, as well as a variety of medical conditions and genetic variants. Congestive heart failure and AF share common mechanisms, including myocardial fibrosis and dysregulation of intracellular calcium and neuroendocrine function. Pharmacological treatments including beta-blockers, digoxin, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers can be useful in treating both of these conditions. Antiarrhythmic medications intended to achieve and maintain sinus rhythm may be beneficial in some patients with AF and CHF. Advances in pacemaker and defibrillator therapy, including cardiac resynchronization therapy, may also benefit patients with AF and CHF. Surgical and catheter-based ablation therapy can restore sinus rhythm in patients with AF, with proven benefit in patients with concommitant CHF. Investigational biologic therapy, including cell and gene based therapy, offers promise for the future of reversing the pathophysiological mechanisms that underlie AF and CHF.

Comparison of rate control and rhythm control in patients with atrial fibrillation after percutaneous mitral balloon valvotomy: a randomised controlled study

OBJECTIVE

To compare rate control and rhythm control strategies in patients with atrial fibrillation (AF) after percutaneous mitral balloon valvotomy (PMV).

METHODS

183 patients with AF after successful PMV, with AF duration <or= 12 months and post-PMV left atrial (LA) size <or= 45 mm, were studied in a prospective, randomised trial. The primary end point was improvement in AF-related symptoms. Secondary study end points were 6 min walk tests, quality of life (QOL), normalisation of LA size, number of hospital admissions and duration of hospital stay.

RESULTS

Over one year, 2% patients in the rate control group had sinus rhythm, as compared with 96% of patients in the rhythm control group (p < 0.001). A greater proportion of patients reported improvement in symptoms in the rhythm control group than in the rate control group (p < 0.0001 at every visit time). Walking distance in a 6 min walk test, QOL and LA size normalisation were better in the rhythm control group than in the rate control group. The strategy of rhythm control was associated with similar numbers of hospital admissions but with longer duration of hospital admissions. Drug-related side effect did not differ between the rate control and rhythm control groups. During the follow-up period, no patients in either group had embolic or transitory ischaemic neurological events.

CONCLUSIONS

In patients with AF after PMV, AF duration <or= 12 months and post-PMV LA size <or= 45 mm, sinus rhythm was easy and safe to achieve and maintain. Moreover, patients benefited from restoration and maintenance of sinus rhythm in terms of improved AF-related symptoms, 6 min walk tests and QOL, and of LA size normalisation. Rhythm control should therefore be considered as the preferred initial therapy for this group of patients. The optimal strategy to treat AF after PMV should be individualised.

Targeted pharmacological reversal of electrical remodeling after cardioversion--rationale and design of the Flecainide Short-Long (Flec-SL) trial

Persistent atrial fibrillation (AF) causes relevant mortality and cardiovascular and noncardiovascular morbidity. Therefore, maintenance of sinus rhythm is an important clinical goal, especially when the patient is symptomatic, despite the fact that current treatment strategies are not sufficient to completely prevent recurrent AF. In addition to underlying atrial disease that predisposes to AF, AF in itself induces structural and electrical adaptations ("electrical remodeling" and "structural remodeling"). Underlying disease processes and parts of structural remodeling are not always reversible. Electrical remodeling, in contrast, is reversed by a few weeks of maintenance of sinus rhythm under experimental conditions. This corresponds to the period when most of the recurrent episodes of AF occur after cardioversion. Antiarrhythmic drugs that prolong the atrial action potential can assist in the prevention of recurrent AF by promoting the reversal of electrical remodeling. Such drugs, which are currently used over long periods after cardioversion, may only be needed until the physiological action potential duration is restored, for example, during the first few weeks after cardioversion of persistent AF. This treatment concept that we call "targeted pharmacological reversal of electrical remodeling" would limit both cost and drug-induced side effects of antiarrhythmic drug therapy after cardioversion. The Flec-SL trial, ISECTN62728743, therefore tests the main hypothesis that targeted pharmacological reversal of electrical remodeling by short-term antiarrhythmic drug therapy for 4 weeks after cardioversion is not inferior to standard long-term antiarrhythmic drug therapy for the prevention of recurrent AF after cardioversion in a parallel group, randomized, multicenter, open, blinded end point analysis design. Based on its effectiveness and pharmacokinetic profile, flecainide is used to test the study hypothesis. The trial uses daily transtelephonic electrocardiographic monitoring for all patients and will be conducted within the German Atrial Fibrillation Competence NETwork (AFNET) to facilitate inclusion of patients from electrophysiologically oriented cardiology centers, ordinary hospitals, and office-based physicians.

Recent Publications on Medications and Pharmacy

Hospital Pharmacy presents a new feature to keep pharmacists abreast of new publications in the medical/pharmacy literature. Articles of interest will be abstracted monthly regarding a broad scope of topics.

Biochemistry and biology of mammalian DNA methyltransferases

DNA methylation is a stable but not irreversible epigenetic signal that silences gene expression. It has a variety of important functions in mammals, including control of gene expression, cellular differentiation and development, preservation of chromosomal integrity, parental imprinting and X-chromosome inactivation. In addition, it has been implicated in brain function and the development of the immune system. Somatic alterations in genomic methylation patterns contribute to the etiology of human cancers and ageing. It is tightly interwoven with the modification of histone tails and other epigenetic signals. Here we review our current understanding of the molecular enzymology of the mammalian DNA methyltransferases Dnmt1, Dnmt3a, Dnmt3b and Dnmt2 and the roles of the enzymes in the above-mentioned biological processes.