Dronedarone for maintenance of sinus rhythm in atrial fibrillation or flutter

Atrial fibrillation in the elderly

Atrial fibrillation (AF) is the most common arrhythmia in older adults with a prevalence of 9 % in adults aged 80 years or older. AF patients have a five times greater risk of developing stroke than the general population. Using anticoagulants for stroke prevention in the elderly becomes a challenge because both stroke and bleeding complications increase with age. CHA₂DS₂-VASc and HAS-BLED scores are currently used as stroke and bleeding risk evaluations. When the HAS-BLED score is 3 or higher, caution and efforts to correct reversible risk factors are advised. Regardless of the HAS-BLED score, warfarin or novel oral anticoagulants are a IIa recommendation for CHA₂DS₂-VASc of 1, except for a score of 1 for females, and a IA recommendation for the score of 2 or higher. Aspirin is no longer recommended for AF thromboprophylaxis. In an elderly patient, lenient rate control is preferred over rhythm control owing to fewer adverse drugs effects and hospitalizations. When rhythm control is needed, dronedarone is a new antiarrhythmic drug that can be considered in patients who have paroxysmal AF and no history of heart failure. Although less efficacious than amiodarone, dronedarone has a fewer thyroid, neurologic, dermatologic, and ocular side effects than amiodarone.

Effect of dronedarone on clinical end points in patients with atrial fibrillation and coronary heart disease: insights from the ATHENA trial

AIMS

This study aimed to assess safety and cardiovascular outcomes of dronedarone in patients with paroxysmal or persistent atrial fibrillation (AF) with coronary heart disease (CHD). Coronary heart disease is prevalent among AF patients and limits antiarrhythmic drug use because of their potentially life-threatening ventricular proarrhythmic effects.

METHODS AND RESULTS

This post hoc analysis evaluated 1405 patients with paroxysmal or persistent AF and CHD from the ATHENA trial. Follow-up lasted 2.5 years, during which patients received either dronedarone (400 mg twice daily) or a double-blind matching placebo. Primary outcome was time to first cardiovascular hospitalization or death due to any cause. Secondary end points included first hospitalization due to cardiovascular events. The primary outcome occurred in 350 of 737 (47%) placebo patients vs. 252 of 668 (38%) dronedarone patients [hazard ratio (HR) = 0.73; 95% confidence interval (CI) = 0.62-0.86; P = 0.0002] without a significant increase in number of adverse events. In addition, 42 of 668 patients receiving dronedarone suffered from a first acute coronary syndrome compared with 67 of 737 patients from the placebo group (HR = 0.67; 95% CI = 0.46-0.99; P = 0.04).

CONCLUSION

In this post hoc analysis, dronedarone on top of standard care in AF patients with CHD reduced cardiovascular hospitalization or death similar to that in the overall ATHENA population, and reduced a first acute coronary syndrome. Importantly, the safety profile in this subpopulation was also similar to that of the overall ATHENA population, with no excess in proarrhythmias. The mechanism of the cardiovascular protective effects is unclear and warrants further investigation.

Impact of atrial fibrillation on outcomes in heart failure

The prevalence of atrial fibrillation (AF) and heart failure increases with advancing age. It is estimated that the annual incidence of AF in the general heart failure population is approximately 5%, whereas as many as 40% of patients with advanced heart failure have AF. The goals of therapy in patients with heart failure and AF are symptom control and prevention of arterial thromboembolism. The adverse hemodynamic events of AF may lead to symptom deterioration and reduced exercise capacity. This review addresses the impact of AF on heart failure outcomes as they pertain to prognosis and management.

Improving outcomes in patients with atrial fibrillation: rationale and design of the Early treatment of Atrial fibrillation for Stroke prevention Trial

BACKGROUND

Even on optimal therapy including anticoagulation and rate control, major cardiovascular complications (stroke, cardiovascular death, and acute heart failure) are common in patients with atrial fibrillation (AF). Conceptually, maintenance of sinus rhythm could prevent adverse outcomes related to AF. Rhythm control therapy has been only moderately effective in published trials, and its potential benefit was offset by side effects of repeated interventions.

RATIONALE

Rhythm control therapy applied early after the first diagnosis of AF could preserve atrial structure and function and maintain sinus rhythm more effectively than the current practice of delayed rhythm control (when symptoms persist after otherwise effective rate control). Furthermore, catheter ablation and new antiarrhythmic drugs have enhanced the potential effectiveness and safety of rhythm control therapy. The EAST will test whether an early, modern rhythm control therapy can reduce cardiovascular complications in AF.

DESIGN

The EAST (Early treatment of Atrial fibrillation for Stroke prevention Trial) will randomize approximately 3,000 patients with recent onset AF at risk for stroke (CHA₂DS₂VASc score ≥2) to either guideline-mandated usual care or to usual care plus early rhythm control therapy in a prospective, randomized, open, blinded outcome assessment trial. All patients will be followed up until the end of the trial for the composite primary outcome of cardiovascular death, stroke, worsening of heart failure, and myocardial infarction. Nights spent in hospital will be counted as a coprimary outcome. Usual care will consist of anticoagulation, therapy of underlying heart disease, and rate control as an initial approach. Early rhythm control therapy will consist of usual care plus rhythm control therapy by antiarrhythmic drugs, catheter ablation, and a patient-operated electrocardiographic device to monitor the ongoing rhythm. Key secondary outcomes include cognitive function and quality of life.

CONCLUSION

EAST will determine whether rhythm control therapy, when applied early after the initial diagnosis of AF, can prevent cardiovascular complications associated with AF.

Pleiotropic effects of antiarrhythmic agents: dronedarone in the treatment of atrial fibrillation

Atrial fibrillation remains the most common arrhythmia in clinical practice. Dronedarone is an antiarrhythmic drug for the maintenance of sinus rhythm in patients with atrial fibrillation. Dronedarone is an amiodarone derivative developed to reduce the number of extracardiovascular side effects. Dronedarone has undergone extensive experimental and clinical testing during the last decade. On the aggregate, these studies have highlighted a complex set of pleiotropic actions that may contribute to dronedarone's antiarrhythmic effects. In this review, we summarize the clinical studies that have evaluated dronedarone and provide an overview of dronedarone's electrophysiological and nonelectrophysiological pleiotropic actions.

Antiarrhythmic drugs in atrial fibrillation: do they have a future?

Atrial fibrillation (AF) is a common arrhythmia associated with significant morbidity and mortality. There has been much debate about the relative merits of rate vs rhythm control strategies, and studies to date have failed to show advantage with a rhythm-control strategy using antiarrhythmic drugs (AADs). This is likely because of the inadequacies of our current AADs and the limitations of study designs. However, there is evidence that AADs improve symptoms and quality of life (QOL). Until trials are performed with more appropriate patient selection, and end points and better AADs and strategies for their use, rhythm control should not be abandoned and may continue to be beneficial in selected patients.

Management of atrial fibrillation in chronic kidney disease: double trouble

Chronic kidney disease (CKD) has a very well-established link with cardiovascular disease. Below stage 3 CKD (glomerular filtration rate <60 mL/min), there is a progressive increase in both total mortality and cardiovascular-specific mortality as kidney function declines; indeed, it is more likely for a patient with CKD stage 3 to die of cardiovascular disease than to progress to CKD stage 4 and beyond. Arrhythmia is particularly common in patients with CKD. Depending on the study and measurement used, the prevalence of patients with CKD with chronic atrial fibrillation (AF) is quoted at 7% to 18%, rising to 12% to 25% for those older than 70 years. These rates are up to 2 to 3 times higher than in the general population. Of all patients with AF, 10% to 15% will have CKD. However, not all standard rate and rhythm methods are suitable for this population and those that are tend to be less effective. Meanwhile, anticoagulation has long been a thorny subject, with much conflicting evidence around the balance between bleeding and stroke risk. To help clarify this, we first highlight the challenges of performing evidence-based medicine in the patient with renal disease, and then review recent and emerging research to suggest an approach to the management of patients with renal disease who have AF. We also review the potential role of the different new oral anticoagulant drugs in CKD.

Appropriate and inappropriate use of dronedarone in 2013

OPINION STATEMENT

Dronedarone is a multichannel blocking antiarrhythmic agent that has been shown to prevent atrial fibrillation/flutter (AF/AFl) recurrences in several multi-center trials. In the ANDROMEDA trial, dronedarone treatment increased mortality and cardiovascular hospitalizations patients with decompensated heart failure. In the ATHENA trial, dronedarone was used in elderly high risk patients with paroxysmal or persistent AF/AFl, excluding those with advanced heart failure, cardiovascular hospitalizations were significantly reduced. Dronedarone increased mortality and cardiovascular hospitalizations in a different patient group with permanent AF/AFl. Although organic toxicity from the drug is very rare, post-marketing data has reported rare hepatic toxicity associated with dronedarone use. Current guidelines position dronedarone as a front-line antiarrhythmic in many patients with AF/Fl. However, dronedarone should not be used in patients with advanced heart failure or in permanent AF. Clinical trial results have helped us define appropriate and inappropriate candidates for dronedarone.

Benefit-risk assessment of dronedarone in the treatment of atrial fibrillation

Rhythm control in atrial fibrillation (AF) can be achieved using pharmacological therapy. Amiodarone is the most efficacious anti-arrhythmic agent; however, its use is limited due to an unfavourable safety profile, including pro-arrhythmia, thyroid, liver, skin and pulmonary complications. Dronedarone, which is structurally similar to amiodarone, was developed to try and achieve a favourable balance of efficacy and risk. Dronedarone has been evaluated in several large clinical trials, which have shown reduced mortality and hospitalization rates in patients with non-permanent AF. In patients with permanent AF and/or heart failure, dronedarone has been shown to cause increased mortality and morbidity and should not be used in these groups. Compared with amiodarone, dronedarone has fewer toxic effects (thyroid, skin, pulmonary) and, although less efficacious, may be used as first-line therapy for maintenance of sinus rhythm in patients with non-permanent AF. Clinicians must be vigilant in monitoring their patients to ensure they do not develop permanent AF or heart failure.

Anti-Arrhythmic Agents in the Treatment of Atrial Fibrillation

Although atrial fibrillation (AF) is the most common sustained arrhythmia seen during daily cardiovascular physician practice, its management remained a challenge for cardiology physician as there was no single anti-arrhythmic agents proved to be effective in converting atrial fibrillation and kept its effectiveness in maintaining sinus rhythm over long term. Moreover all the anti-arrhythmic agents that are used in treatment of AF were potentially pro-arrhythmic especially in patients with coronary artery disease and structurally abnormal heart. Some of these drugs also have serious non cardiac side effects that limit its long term use in the management of atrial fibrillation. Several new and investigational anti-arrhythmic agents are emerging but data supporting their effectiveness and safety are still limited. In this systematic review we examine the efficacy and safety of these medications supported by the major published randomized trials, meta-analyses and review articles and conclude with a summary of guidelines recommendations.

Management of late arrhythmias in adults with repaired congenital heart disease

OPINION STATEMENT

As survival of patients with congenital heart disease improves with surgery and the population of patients with repaired adult congenital heart disease (ACHD) age, understanding complications such as arrhythmias has become more important. Arrhythmias account for significant morbidity and mortality in the ACHD population. Atrial arrhythmias occur in 15 % of patients with ACHD and, in patients with severe congenital heart disease (CHD), more than 50 % develop atrial arrhythmias by the age of 65 years [1]. This article aims to give an overview of arrhythmias seen in the ACHD population and the treatment modalities available now.

Cross-trial comparisons: a source of confusion, use, or both in the management of patients with atrial fibrillation?

Many medical therapies are shaped by clinical trial data. However, individual clinical trial results sometimes appear discordant for the same tested treatments, and competing treatment strategies are often not directly tested. Clinicians are forced to make decisions by extrapolating information from different trials of similar but nonidentical therapies. In an era where increasing medical complexity demands sound evidence-based decisions, clinicians must navigate through these issues to arrive at optimal patient-specific management decisions. Using trials investigating therapies for atrial fibrillation, we attempt to highlight the important points for practitioners to consider when making these comparative intertrial judgments.

Practice implications of the Atrial Fibrillation Guidelines

Atrial fibrillation is one of the most common and complex cardiac arrhythmias. Using currently available evidence, leading medical societies have established recommendations for the optimal management of atrial fibrillation. These guidelines have recently been updated by 4 consensus groups: the European Society of Cardiology, the American College of Chest Physicians, the Canadian Cardiovascular Society, and a task force of 3 societies from the United States: the American College of Cardiology Foundation, the American Heart Association, and the Heart Rhythm Society. The present review focused on the similarities and differences among these recently updated guidelines. Key revisions included updated information on newer treatments for rhythm control, treatment options to reduce atrial fibrillation complications, and updated anticoagulant management for thromboprophylaxis.

Which patient is most likely to benefit from dronedarone? Analysis from the Magdeburg Dronedarone Registry (MADRE study)

Based on an analysis of the Magdeburg Dronedarone Registry data we sought to determine which patients could benefit from dronedarone therapy regarding rhythm control. The study included 191 patients (85 women) aged 63 ± 10 years with a history of paroxysmal or persistent AF and a follow-up of 14 ± 5 months. The total AF recurrence rate was 67% and lone AF was significantly more often associated with AF recurrences than non-lone AF (84% vs. 62%, P = .01). Arterial hypertension, treated coronary artery disease, and diabetes mellitus were not significantly related to AF recurrences (64%, 67%, 58% resp. P = .3). Response rate to dronedarone in patients with slightly increased left atrial size was significantly greater than in patients with normal or markedly increased left atrial size (47%, 16%, 27% resp., P = .001). The rate of adverse effects was 32% in the study sample, and was significantly lower in patients with lone AF as compared to those with non-lone AF (11% vs. 37%, P = .002). The body mass index was a predictor neither of response rate nor adverse effects. The results suggest that dronedarone is more effective in patients with non-lone AF and slightly increased left atrial size.

Novel anti-arrhythmic medications in the treatment of atrial fibrillation

Atrial fibrillation (AF) is a prevalent condition particularly amongst the elderly, which contributes to both morbidity and mortality. The burden of disease has lead to significant increases in health care utilization and cost in recent years. Treatment of Atrial fibrillation consists of either a rate or rhythm control strategy. Rhythm control is achieved using medical management and/or catheter ablation. In spite of major strides in catheter ablation, this procedure remains a second line treatment of AF. Anti-arrhythmic medications represent the main treatment modality for the maintenance of sinus rhythm. Amiodarone has been used for decades because of its efficacy and lack of pro-arrhythmia despite numerous extra-cardiac side effects. Novel agents such as Dronedarone were designed to emulate Amiodarone without the extra-cardiac side effects. Unfortunately recent trials have raised concerns for the safety of this medication in certain patients. Other agents such as Vernakalant and Ranolazine are in development that promise to be more atrial selective in their action, thereby potentially avoiding pro-arrhythmia and heart failure side effects. It remains to be seen however if one or more of these agents achieves the required high efficacy and safety threshold. This review summarizes the main anti-arrhythmic clinical trials, early phase trials involving novel agents and examines the conflicting data relating to Dronedarone.

Atrial fibrillation and heart failure in the elderly

Atrial fibrillation (AF) is a common clinical problem in elderly patients and especially in those with heart failure (HF). It is a major risk factor for serious cardiovascular events, such as stroke, HF and premature death. Both the prevalence and incidence of AF increase with age and its prevalence in the United States are estimated at more than 2.2 million, with nearly 75% of patients aged >65 years. Aging-related atrial remodeling with fibrosis, dilation and mitochondrial DNA mutations predispose elderly patients to AF. Current management options for AF, including rate control and anticoagulation therapy, can be successfully applied to the elderly population. New antiarrhythmic and anticoagulation medications such as dronedarone and dabigatran, respectively, can impact the approach to therapy in the elderly. Non-pharmacological options such as catheter-based ablation have also gained prominence and have been incorporated into the guidelines for management of AF. However, more trials in the elderly and very elderly segments are needed to clarify the safety and long-term efficacy of the new treatment options.

Dronedarone's inhibition of If current is the primary mechanism responsible for its bradycardic effect

INTRODUCTION

The mechanism(s) whereby dronedarone reduces sinus rate are not well understood, although L-type calcium channel antagonism, beta-adrenergic blockade, and inhibition of If are plausible.

METHODS AND RESULTS

In anesthetized pigs, we compared the effects of dronedarone to the prototypical If inhibitor, ivabradine, and the L-type calcium channel antagonist diltiazem on heart rate, mean arterial blood pressure (MAP), and contractility. Dronedarone's effects on the phenylephrine-induced rise in MAP and on the chronotropic response to isoproterenol were also investigated. Cumulative doses of dronedarone (0.5 mg/kg, i.v., and 5.0 mg/kg, i.v.; plasma level: 80 ± 16.1 nM) progressively reduced heart rate (P < 0.02) without changes in MAP or contractility as assessed by LV dP/dt (N = 6). Ivabradine (0.5 mg/kg, i.v.) similarly reduced heart rate (P < 0.01) without change in MAP (N = 6). Diltiazem (0.8 mg/kg, i.v.) reduced heart rate and MAP and decreased contractility (N = 6). Dronedarone blunted phenylephrine's alpha-receptor-mediated increase in MAP but did not alter the marked beta-adrenergic receptor (BAR)-mediated increase in heart rate induced by isoproterenol. When dronedarone injection was preceded by ivabradine, no further decrease in heart rate or change in MAP was observed (N = 6).

CONCLUSIONS

Dronedarone reduced heart rate without affecting MAP or contractility, effects that differ from L-type calcium channel blockade. Dronedarone did not antagonize BAR stimulation, and its heart-rate lowering effects were eliminated by prior administration of ivabradine. Thus, dronedarone's bradycardic action is likely due to inhibition of If and not to blockade of either L-type calcium channels or BAR.

Usefulness of dronedarone in patients with atrial arrhythmias

Dronedarone is a novel class III antiarrhythmic drug with moderate efficacy in preventing atrial arrhythmias. However, only few data from the real-world use of dronedarone with limited electrocardiographic monitoring are available. The investigators report the incidence, timing, and reasons for discontinuation of dronedarone; maintenance of sinus rhythm; and atrial arrhythmia recurrence patterns in 120 consecutive patients with atrial fibrillation (AF; n = 91) or non-isthmus-dependent atrial flutter (n = 29) treated with dronedarone (400 mg twice daily). Rhythm control was assessed with serial 7-day Holter electrocardiography after 4 weeks and after 6 to 9 months. After drug initiation, dronedarone was discontinued in 19 patients (16%) because of inefficacy (n = 7 [6%]) or adverse events (n = 12 [10%]). At 4 weeks, 44 patients (37%) had stopped taking dronedarone because of inefficacy (n = 27 [23%]) or adverse events (n = 17 [14%]). After 6 to 9 months, 25 patients (21%) had discontinued dronedarone because of clinical inefficacy (n = 16 [13%]) or adverse events (n = 9 [8%]). Overall, dronedarone was still used after 6 to 9 months in 32 patients (27%). Maintenance of sinus rhythm was achieved in 40 patients (33%) after 4 weeks and in 24 patients (20%) after 6 to 9 months. Reversal from persistent to paroxysmal arrhythmias was observed in 23 patients, (29%) whereas progression from paroxysmal to persistent arrhythmias occurred in 6 patients (15%). Conversion from AF to non-isthmus-dependent atrial flutter was noted in 10 patients (13%). In conclusion, dronedarone is associated with frequent adverse events and moderate antiarrhythmic efficacy requiring discontinuation in most patients within the first 9 months of use, and there is a prevalent reversal from persistent to paroxysmal but also from paroxysmal to persistent atrial arrhythmias and from AF to non-isthmus-dependent atrial flutter.

Dronedarone: Where Does it Fit in the AF Therapeutic Armamentarium?

Dronedarone is a derivative of amiodarone with similar mechanisms of action (blocking calcium, potassium and sodium channels in addition to having anti-adrenergic effects). Compared to amiodarone it has fewer drug interactions (though it can interact with all current anticoagulants), more limited risk of organ toxicity, a much shorter half-life with no need for a loading regimen, but lower efficacy. Dronedarone is approved for the treatment of atrial fibrillation; has had limited studies for other arrhythmias; and has no adverse drug-ICD interactions reported. Clinical trials have resulted in only one dosing regimen (400 mg bid, to be taken with food) and have demonstrated both rate and rhythm effects in atrial fibrillation (AF). Dronedarone slows the ventricular response, can prolong the time to/reduce recurrences of/ reduce progression of AF, and reduce the incidence of hospitalization in AF patients with risk-prone markers. However, trials have also revealed an increased risk of mortality and other adverse cardiovascular outcomes from dronedarone when given to patients in heart failure. The details of these trials, additional pharmacokinetic and pharmacodynamic information, and recommendations concerning the use of dronedarone are provided in the full manuscript that follows.

Cardiac ion channels and mechanisms for protection against atrial fibrillation

Atrial fibrillation (AF) is recognised as the most common sustained cardiac arrhythmia in clinical practice. Ongoing drug development is aiming at obtaining atrial specific effects in order to prevent pro-arrhythmic, devastating ventricular effects. In principle, this is possible due to a different ion channel composition in the atria and ventricles. The present text will review the aetiology of arrhythmias with focus on AF and include a description of cardiac ion channels. Channels that constitute potentially atria-selective targets will be described in details. Specific focus is addressed to the recent discovery that Ca(2+)-activated small conductance K(+) channels (SK channels) are important for the repolarisation of atrial action potentials. Finally, an overview of current pharmacological treatment of AF is included.

Mechanisms of ranolazine's dual protection against atrial and ventricular fibrillation

Coronary artery disease and heart failure carry concurrent risk for atrial fibrillation and life-threatening ventricular arrhythmias. We review evidence indicating that at therapeutic concentrations, ranolazine has potential for dual suppression of these arrhythmias. Mechanisms and clinical implications are discussed.

New-onset atrial fibrillation is a predictor of subsequent hyperthyroidism: a nationwide cohort study

AIMS

To examine the long-term risk of hyperthyroidism in patients admitted to hospital with new-onset AF. Hyperthyroidism is a well-known risk factor for atrial fibrillation (AF), but it is unknown whether new-onset AF predicts later-occurring hyperthyroidism.

METHODS AND RESULTS

All patients admitted with new-onset AF in Denmark from 1997-2009, and their present and subsequent use of anti-thyroid medication was identified by individual-level linkage of nationwide registries. Patients with previous thyroid diagnosis or thyroid medication use were excluded. Development of hyperthyroidism was assessed as initiation of methimazole or propylthiouracil up to a 13-year period. Risk of hyperthyroidism was analysed by Poisson regression models adjusted for important confounders such as amiodarone treatment. Non-AF individuals from the general population served as reference. A total of 145,623 patients with new-onset AF were included (mean age 66.4 years [SD ±13.2] and 55.3% males) of whom 3% (4,620 events; 62.2% women) developed hyperthyroidism in the post-hospitalization period compared to 1% (48,609 events; 82% women) in the general population (n = 3,866,889). In both women and men we found a significantly increased risk of hyperthyroidism associated with new-onset AF compared to individuals in the general population. The highest risk was found in middle-aged men and was consistently increased throughout the 13-year period of observation. The results were confirmed in a substudy analysis of 527,352 patients who had thyroid screening done.

CONCLUSION

New-onset AF seems to be a predictor of hyperthyroidism. Increased focus on subsequent risk of hyperthyroidism in patients with new-onset AF is warranted.

Current and emerging antiarrhythmic drug therapy for ventricular tachycardia

Ventricular arrhythmias, including ventricular fibrillation (VF) and sustained ventricular tachycardia (VT), are the principal causes of sudden cardiac death in patients with structural heart disease. While coronary artery disease is the predominant substrate associated with the development of VT, these arrhythmias are known to occur in a variety of disorders, including dilated cardiomyopathy, valvular and congenital heart disease, and cardiac ion channelopathies such as the long QT syndrome. In a minority of patients, VT occurs in the absence of structural heart disease. Despite the established mortality benefit of the implantable cardioverter defibrillator (ICD) in patients at risk of lethal arrhythmias, recurrent VT/VF events continue to be a source of morbidity and impaired quality of life in such patients. Antiarrhythmic therapy is indicated in select patients to treat symptomatic VT episodes, to reduce the incidence of ICD shocks, and potentially to improve quality of life and reduce hospitalizations related to cardiac arrhythmia. The primary adverse effects of antiarrhythmic medications are related to both cardiac and extracardiac toxicity, including the risk of proarrhythmia. Current drug therapy for ventricular arrhythmia has been limited by suboptimal efficacy in many patients, resulting in recurrent VT/VF events, and by drug toxicity or intolerance leading to discontinuation in a large percentage of patients. Amiodarone and sotalol are the principal agents used in the chronic treatment of VT. In addition, dronedarone and dofetilide, agents approved for the treatment of atrial fibrillation, and ranolazine, an antianginal agent, have been demonstrated to be protective against ventricular arrhythmia in small clinical studies. Finally, advances in basic electrophysiology have uncovered new molecular targets for the treatment of ventricular arrhythmia, and pharmacologic agents directed at these targets may emerge as promising VT treatments in the future. The roles of these current and emerging therapies for the treatment of VT in humans will be summarized in this review.

Atrial fibrillation and stroke: the evolving role of rhythm control

OPINION STATEMENT

Atrial fibrillation (AF) remains a major risk factor for stroke. Unfortunately, clinical trials have failed to demonstrate that a strategy of rhythm control--therapy to maintain normal sinus rhythm (NSR)--reduces stroke risk. The apparent lack of benefit of rhythm control likely reflects the difficulty in maintaining NSR using currently available therapies. However, there are signals from several trials that the presence of NSR is indeed beneficial and associated with better outcomes related to stroke and mortality. Most electrophysiologists feel that as rhythm control strategies continue to improve, the crucial link between rhythm control and stroke reduction will finally be demonstrated. Therefore, AF specialists tend to be aggressive in their attempts to maintain NSR, especially in patients who have symptomatic AF. A step-wise approach from antiarrhythmic drugs to catheter ablation to cardiac surgery is generally used. In select patients, catheter ablation or cardiac surgery may supersede antiarrhythmic drugs. The choice depends on the type of AF, concurrent heart disease, drug toxicity profiles, procedural risks, and patient preferences. Regardless of strategy, given the limited effectiveness of currently available rhythm control therapies, oral anticoagulation is still recommended for stroke prophylaxis in AF patients with other stroke risk factors. Major challenges in atrial fibrillation management include selecting patients most likely to benefit from rhythm control, choosing specific antiarrhythmic drugs or procedures to achieve rhythm control, long-term monitoring to gauge the efficacy of rhythm control, and determining which (if any) patients may safely discontinue anticoagulation if long-term NSR is achieved.

Effects of dronedarone started rapidly after amiodarone discontinuation

BACKGROUND

Multiple studies have shown that amiodarone is effective in treating atrial fibrillation (AF), but is associated with a relatively high incidence of side effects; however, due to amiodarone's long elimination half-life (20-100 days), physicians may hesitate to start other drugs until it has fully cleared.

HYPOTHESIS

A rapid switch from amiodarone to dronedarone is feasible.

METHODS

EURIDIS and ADONIS were double-blind, multinational, parallel-group trials comparing the efficacy and safety of dronedarone with placebo over 12 months. This retrospective subanalysis of EURIDIS/ADONIS compared the effects of dronedarone in patients discontinuing amiodarone within 2 days before randomization ("rapid switch") with results in patients who had received no amiodarone during the 2 months preceding randomization.

RESULTS

In total, 1237 patients were enrolled ("rapid switch", n = 154; "no amiodarone", n = 1014). In both the "rapid switch" and the "no amiodarone" groups, dronedarone users had significantly lower AF recurrence than patients receiving placebo (HR = 0.64, 95% CI, 0.44-0.95; P = 0.0224 and HR = 0.79, 95% CI, 0.67-0.92; P = 0.0027, respectively). Dronedarone users had a higher incidence of bradyarrhythmic events than placebo-treated patients. A "rapid switch" from amiodarone to dronedarone was associated with a higher incidence of serious heart failure events and heart failure hospitalizations versus all other groups. Overall event rates were low and there was no significant difference in total adverse event rates or deaths between groups.

CONCLUSION

In this patient population, a switch from amiodarone to dronedarone within a 2-day time frame might be feasible in certain patient categories, but further investigation is warranted.

Role of new drugs for management of atrial fibrillation

OBJECTIVE

To evaluate the role of newer agents in the management of atrial fibrillation (AF).

DATA SOURCES

EMBASE and MEDLINE were searched (up to June 2012) combining medication names with atrial fibrillation, humans, clinical trials, and pharmacoeconomic. References of the articles identified and www.clinicaltrials.gov were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

Studies were limited to the English language with clinical or pharmacoeconomic end points followed by the consensus of 3 authors.

DATA SYNTHESIS

Formulated to reduce some of the adverse effects associated with amiodarone by removing the iodine component, dronedarone has improved clinical outcomes over placebo when used in paroxysmal or persistent AF; however, it is less efficacious than amiodarone. Worse outcomes with dronedarone have been seen in patients with heart failure or permanent AF. It has not been compared to antiarrhythmic agents other than amiodarone, and pharmacoeconomic evaluations are lacking. Dabigatran 150 mg is superior to warfarin in preventing stroke or systemic embolism and has been associated with lower rates of vascular-associated mortality. Although the rates of major bleeding were not significantly different between the 2 agents, gastrointestinal bleeding and myocardial infarction occurred more frequently with dabigatran. Dabigatran appears to have the most pharmacoeconomic benefit over warfarin in patients with a higher risk of stroke. Rivaroxaban is noninferior to warfarin for the prevention of stroke and systemic embolism, with no difference in the rates of major bleeding. Cost-effectiveness studies have not been performed with this agent at this time. In patients with AF who were not suitable candidates for warfarin, apixaban is superior to aspirin in preventing stroke or systemic embolism without increasing the risk for major bleeding. Additionally, apixaban is superior to warfarin in preventing stroke or systemic embolism, results in fewer bleeding events, and is associated with lower mortality. Apixaban is not cost-effective against aspirin when used for a short duration but gains superiority with prolonged use or in patients with higher risks of stroke. Additionally, apixaban appears to offer a pharmacoeconomic advantage over warfarin at no to minimal cost. Each new anticoagulant lacks a reversal agent and an assay to detect the presence of the anticoagulant, as well as long-term data when used in the clinical setting.

CONCLUSIONS

Use of dronedarone should be limited to patients with paroxysmal or persistent AF and should not be used in patients with heart failure or with permanent AF. Newer antithrombotic agents appear to be promising alternatives for the prevention of stroke in patients with AF; however, more data are needed to understand their role.

Mechanisms of hepatocellular toxicity associated with dronedarone--a comparison to amiodarone

Dronedarone is a new antiarrhythmic drug with an amiodarone-like benzofuran structure. Shortly after its introduction, dronedarone became implicated in causing severe liver injury. Amiodarone is a well-known mitochondrial toxicant. The aim of our study was to investigate mechanisms of hepatotoxicity of dronedarone in vitro and to compare them with amiodarone. We used isolated rat liver mitochondria, primary human hepatocytes, and the human hepatoma cell line HepG2, which were exposed acutely or up to 24h. After exposure of primary hepatocytes or HepG2 cells for 24h, dronedarone and amiodarone caused cytotoxicity and apoptosis starting at 20 and 50 µM, respectively. The cellular ATP content started to decrease at 20 µM for both drugs, suggesting mitochondrial toxicity. Inhibition of the respiratory chain required concentrations of ~10 µM and was caused by an impairment of complexes I and II for both drugs. In parallel, mitochondrial accumulation of reactive oxygen species (ROS) was observed. In isolated rat liver mitochondria, acute treatment with dronedarone decreased the mitochondrial membrane potential, inhibited complex I, and uncoupled the respiratory chain. Furthermore, in acutely treated rat liver mitochondria and in HepG2 cells exposed for 24h, dronedarone started to inhibit mitochondrial β-oxidation at 10 µM and amiodarone at 20 µM. Similar to amiodarone, dronedarone is an uncoupler and an inhibitor of the mitochondrial respiratory chain and of β-oxidation both acutely and after exposure for 24h. Inhibition of mitochondrial function leads to accumulation of ROS and fatty acids, eventually leading to apoptosis and/or necrosis of hepatocytes. Mitochondrial toxicity may be an explanation for hepatotoxicity of dronedarone in vivo.

Atrial fibrillation and atrial flutter: medical management

Atrial fibrillation (AF) and atrial flutter (AFL) are common cardiac arrhythmias in older adults. Medical management focuses on rate and rhythm control of AF and AFL to promote symptomatic relief and avoid tachycardia-mediated cardiomyopathy. Pharmacologic treatment of AF and AFL is especially challenging in the elderly because of the presence of comorbidities that may affect drug kinetics, and polypharmacy, which may lead to drug interactions. The potential for complications from medications and procedures required to achieve and maintain sinus rhythm must be carefully balanced against the benefits of therapy. This article reviews medical management of AF and AFL specifically relating to rate and rhythm control. The controversy of rate versus rhythm control is also discussed.

Dronedarone-associated acute renal failure: evidence coming from the Italian spontaneous ADR reporting database

AIM

To describe cases of acute renal failure (ARF) and of renal failure (RF) from dronedarone retrieved in the general population during post-marketing surveillance through the Italian spontaneous ADR reporting database.

METHODS

A case by case analysis was performed. Reports codified with the System Organ Class (SOC) term 'urinary system disorders' of the ADR terminology of the World Health Organization associated with dronedarone treatment were selected.

RESULTS

Out of 124,069 ADR reports, in 55 of them dronedarone was listed as the suspected drug. Among these reports, we identified four cases of ARF, two of RF and three cases of increase of blood creatinine submitted by physicians between October 2010 and December 2011. The patient age was from 61 to 84 years and most cases occurred within the first 13 days of initiation of dronedarone therapy (range 6 days-2 months). Only one patient received a co-suspected drug labelled for causing ARF. In all reports but one, positive dechallenge was reported.

CONCLUSIONS

Clinicians should be made aware of the risk of ARF/RF associated with dronedarone and of the need to screen patients appropriately for ARF/RF risk factors before starting dronedarone therapy.

Cardioversion in atrial fibrillation. Focus on recent-onset atrial fibrillation

Atrial fibrillation is the most common sustained arrhythmia encountered in clinical practice. Its prevalence is rising due to an increasing elderly population and the improvement in management of life-threatening diseases such as myocardial infarction and heart failure. Over the past few years effective non-pharmacological treatments, new antiarrhythmics drugs, and anticoagulants have been introduced. Regardless of rate-control or rhythm control strategy, adequate stroke prevention still remains a cornerstone in the treatment of this arrhythmia. This review aims to illustrate the main practical issues in the management of atrial fibrillation, focusing on patients with recent-onset and hemodynamically stable atrial fibrillation.

Dronedarone reduces arterial thrombus formation

Dronedarone has been associated with a reduced number of first hospitalisation due to acute coronary syndromes. Whether this is only due to the reduction in ventricular heart rate and blood pressure or whether other effects of dronedarone may be involved is currently elusive. This study was designed to investigate the role of dronedarone in arterial thrombus formation. C57Bl/6 mice were treated with dronedarone and arterial thrombosis was investigated using a mouse photochemical injury model. Dronedarone inhibited carotid artery thrombus formation in vivo (P < 0.05). Thrombin- and collagen-induced platelet aggregation was impaired in dronedarone-treated mice (P < 0.05), and expression of plasminogen activator inhibitor-1 (PAI1), an inhibitor of the fibrinolytic system, was reduced in the arterial wall (P < 0.05). In contrast, the level of tissue factor (TF), the main trigger of the coagulation cascade, and that of its physiological inhibitor, TF pathway inhibitor, did not differ. Similarly, coagulation times as measured by prothrombin time and activated partial thromboplastin time were comparable between the two groups. Dronedarone inhibits thrombus formation in vivo through inhibition of platelet aggregation and PAI1 expression. This effect occurs within the range of dronedarone concentrations measured in patients, and may represent a beneficial pleiotropic effect of this drug.

Polyunsaturated Fatty acids in atrial fibrillation: looking for the proper candidates

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice with growing prevalence in developed countries. Several medical and interventional therapies, such as atrial specific drugs and pulmonary vein isolation, have demonstrated prevention of recurrences. However, their suboptimal long-term success and significant rate of secondary effects have led to intensive research in the last decade focused on novel alternative and supplemental therapies. One such candidate is polyunsaturated fatty acids (PUFAs). Because of their biological properties, safety, simplicity, and relatively cheap cost, there is a special clinical interest in omega-3 PUFAs as a possible antiarrhythmic agent. Obtained from diets rich in fish, they represent one of the current supplemental therapies. At the cellular level, an increasing body of evidence has shown that n-3 PUFAs exert a variety of effects on cardiac ion channels, membrane dynamic properties, inflammatory cascade, and other targets related to AF prevention. In this article, we review the current basic and clinical evidence pertinent to n-3 PUFAs in AF treatment and prevention. We also discuss controversial outcomes among clinical studies and propose specific subsets of AF patients who will benefit most from n-3 PUFAs.

Effect of ranolazine on ventricular repolarization in class III antiarrhythmic drug-treated rabbits

BACKGROUND

Ranolazine exhibits a synergistic effect in combination with class III drugs to suppress atrial fibrillation.

OBJECTIVE

To investigate whether a combination therapy affects repolarization and provokes ventricular tachyarrhythmias (VT) in a sensitive model of proarrhythmia.

METHODS

Thirty-seven rabbits were assigned to 3 groups and fed with amiodarone (50 mg/kg/d; n = 10) or dronedarone (50 mg/kg/d; n = 10) over a period of 6 weeks. A third group was used as control (n = 17). After obtaining baseline data in Langendorff-perfused control hearts, sotalol (100 μM) was administered in this group. Thereafter, ranolazine (10 μM) was additionally infused on top of amiodarone, dronedarone, or sotalol.

RESULTS

Chronic treatment with amiodarone or dronedarone as well as sotalol significantly increased action potential duration at 90% repolarization (APD(90)). Additional treatment with ranolazine further increased APD(90) in amiodarone- and dronedarone-pretreated hearts but not in sotalol-treated hearts. Ranolazine increased postrepolarization refractoriness as compared with amiodarone or dronedarone alone owing to a marked effect on the refractory period. In contrast to amiodarone and dronedarone, acute application of sotalol increased dispersion of repolarization (P < .05). Additional treatment with ranolazine did not further increase spatial or temporal dispersion. After lowering extracellular [K(+)] in bradycardic hearts, no proarrhythmia occurred in amiodarone- or dronedarone-treated hearts whereas 11 of 17 sotalol-treated hearts showed early afterdepolarizations and subsequent polymorphic VT. Additional treatment with ranolazine reduced the number of VT episodes in sotalol-treated hearts and did not cause proarrhythmia in combination with amiodarone or dronedarone.

CONCLUSIONS

Application of ranolazine on top of class III drugs does not cause proarrhythmia despite a marked effect on ventricular repolarization. The effect of ranolazine on the repolarization reserve is associated with the lack of effect on early afterdepolarizations and dispersion of repolarization.

Latest drug developments in the field of cardiovascular disease

Cardiovascular disease has been responsible for more deaths annually than any other disease category since 1900, except for the influenza epidemic in 1916. Yet, the drug pipeline has been largely bereft of new entrants. In 2008, one new cardiovascular medication was marketed in the United States. In 2009, there were two new cardiovascular medications. In comparison, there were seven new drugs for oncology in 2009. The present review explores new agents within the context of models currently in the drug pipeline. Of course, there is no guarantee that any of these agents will be marketed. A discussion of the models is illustrative of the types of approaches being used to develop new cardiovascular agents.

Meta-analysis of cardiovascular outcomes with dronedarone in patients with atrial fibrillation or heart failure

Dronedarone is a benzofuran derivative approved by the Food and Drug Administration to decrease the risk of cardiovascular hospitalization in patients with paroxysmal or persistent atrial fibrillation (AF) and associated cardiovascular risk factors who are in sinus rhythm or will undergo cardioversion. There has been recent evidence to suggest that dronedarone may not have a favorable safety profile. We decided to evaluate all available evidence on the cardiovascular safety of this drug. A systematic search was made of the PubMed, CENTRAL, and EMBASE databases for randomized controlled trials from 1966 through 2011 comparing dronedarone to comparators in AF/heart failure. Intervention was dronedarone for AF for some studies and heart failure for others. Comparators included standard medical therapy and/or placebo and amiodarone for 1 study. Outcomes assessed were all-cause mortality, cardiovascular mortality, ventricular arrhythmias, embolic events, acute coronary syndrome, heart failure exacerbations, and hospitalization rates in the intervention versus comparator group at the end of ≥ 3 months of follow up with abstraction of data by 1 author. Seven randomized controlled trials were included in our analysis. Dronedarone use was associated with a trend toward worse all-cause and cardiovascular mortalities and increased heart failure exacerbations. It also showed numerically higher event rates for all other outcome events except acute coronary syndrome. Our pooled analysis showed increased all-cause and cardiovascular mortalities and increased heart failure exacerbations with use of dronedarone across a wide spectrum of populations. In conclusion, we recommend exercising caution using dronedarone, especially in patients with cardiovascular risk factors.

Antiarrhythmic drugs for the maintenance of sinus rhythm: risks and benefits

Atrial fibrillation (AF) is the most common arrhythmia seen in clinical practice, and its complications impose a significant economic burden. The development of more effective agents to manage patients with AF is essential. While clinical trials show no major differences in outcomes between rate and rhythm control strategies, some patients with AF require treatment with antiarrhythmic drugs (AADs) to maintain sinus rhythm, reduce symptoms, improve exercise tolerance, and improve quality of life. Currently available AADs, while effective, have limitations including limited efficacy, adverse events, toxicity, and proarrhythmic potential. The 6 most commonly used AADs (amiodarone, disopyramide, dofetilide [USA but not Europe], flecainide, propafenone, sotalol) have proarrhythmic effects (fewer with amiodarone). Amiodarone is the most effective AAD, but its safety profile limits its usefulness. Recent advances in AAD therapy include dronedarone and vernakalant. Dronedarone, approved by the United States Food and Drug Administration and the European Medicines Authority and others, has been proven efficacious in maintaining sinus rhythm and reducing the incidence of hospitalization due to cardiovascular events or death in patients with AF. The intravenous formulation of vernakalant is approved in the European Union, Iceland, and Norway. Oral vernakalant is currently undergoing evaluation for preventing AF recurrence and appears to be effective with an acceptable safety profile. Treatment should be individualized to the patient with consideration of pharmacologic risks and benefits according to AF management guidelines. Accumulating efficacy and safety data for new and emerging AADs holds promise for improved AF management and outcomes.