Pharmacological cardioversion of atrial fibrillation: current management and treatment options

Flecainide Specifically Targets the Monovalent Countercurrent Through the Cardiac Ryanodine Receptor, While a Dominant Opposing Ca2+/Ba2+ Current Is Present

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a highly arrhythmogenic syndrome triggered by stress, primarily linked to gain-of-function point mutations in the cardiac ryanodine receptor (RyR2). Flecainide, as an effective therapy for CPVT, is a known blocker of the surface-membrane Na+ channel, also affecting the intracellular RyR2 channel. The therapeutic relevance of the flecainide-RyR2 interaction remains controversial, as flecainide blocks only the RyR2 current flowing in the opposite direction to the physiological Ca2+ release from the sarcoplasmic reticulum (SR). However, it has been proposed that charge-compensating countercurrent from the cytosol to SR lumen plays a critical role, and its reduction may indeed suppress excessive diastolic SR Ca2+ release through RyR2 channels in CPVT. Monitoring single-channel properties, we examined whether flecainide can target intracellular pathways for charge-balancing currents carried by RyR2 and SR Cl- channels under cell-like conditions. Particularly, the Tris+ countercurrent flowed through the RyR2 channel simultaneously with a dominant reverse Ca2+/Ba2+ current. We demonstrate that flecainide blocked the RyR2-mediated countercurrent without affecting channel activity. In contrast, the SR Cl- channel was completely resistant to flecainide. Based on these findings, it is reasonable to propose that the primary intracellular target of flecainide in vivo is the RyR2-mediated countercurrent.

External electrical and pharmacological cardioversion for atrial fibrillation, atrial flutter or atrial tachycardias: a network meta-analysis

BACKGROUND

Atrial fibrillation (AF) is the most frequent sustained arrhythmia. Cardioversion is a rhythm control strategy to restore normal/sinus rhythm, and can be achieved through drugs (pharmacological) or a synchronised electric shock (electrical cardioversion).

OBJECTIVES

To assess the efficacy and safety of pharmacological and electrical cardioversion for atrial fibrillation (AF), atrial flutter and atrial tachycardias.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, Conference Proceedings Citation Index-Science (CPCI-S) and three trials registers (ClinicalTrials.gov, WHO ICTRP and ISRCTN) on 14 February 2023.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) at the individual patient level. Patient populations were aged ≥ 18 years with AF of any type and duration, atrial flutter or other sustained related atrial arrhythmias, not occurring as a result of reversible causes.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology to collect data and performed a network meta-analysis using the standard frequentist graph-theoretical approach using the netmeta package in R. We used GRADE to assess the quality of the evidence which we presented in our summary of findings with a judgement on certainty. We calculated differences using risk ratios (RR) and 95% confidence intervals (CI) as well as ranking treatments using a P value. We assessed clinical and statistical heterogeneity and split the networks for the primary outcome and acute procedural success, due to concerns about violating the transitivity assumption.

MAIN RESULTS

We included 112 RCTs (139 records), from which we pooled data from 15,968 patients. The average age ranged from 47 to 72 years and the proportion of male patients ranged from 38% to 92%. Seventy-nine trials were considered to be at high risk of bias for at least one domain, 32 had no high risk of bias domains, but had at least one domain classified as uncertain risk, and one study was considered at low risk for all domains. For paroxysmal AF (35 trials), when compared to placebo, anteroapical (AA)/anteroposterior (AP) biphasic truncated exponential waveform (BTE) cardioversion (RR: 2.42; 95% CI 1.65 to 3.56), quinidine (RR: 2.23; 95% CI 1.49 to 3.34), ibutilide (RR: 2.00; 95% CI 1.28 to 3.12), propafenone (RR: 1.98; 95% CI 1.67 to 2.34), amiodarone (RR: 1.69; 95% CI 1.42 to 2.02), sotalol (RR: 1.58; 95% CI 1.08 to 2.31) and procainamide (RR: 1.49; 95% CI 1.13 to 1.97) likely result in a large increase in maintenance of sinus rhythm until hospital discharge or end of study follow-up (certainty of evidence: moderate). The effect size was larger for AA/AP incremental and was progressively smaller for the subsequent interventions. Despite low certainty of evidence, antazoline may result in a large increase (RR: 28.60; 95% CI 1.77 to 461.30) in this outcome. Similarly, low-certainty evidence suggests a large increase in this outcome for flecainide (RR: 2.17; 95% CI 1.68 to 2.79), vernakalant (RR: 2.13; 95% CI 1.52 to 2.99), and magnesium (RR: 1.73; 95% CI 0.79 to 3.79). For persistent AF (26 trials), one network was created for electrical cardioversion and showed that, when compared to AP BTE incremental energy with patches, AP BTE maximum energy with patches (RR 1.35, 95% CI 1.17 to 1.55) likely results in a large increase, and active compression AP BTE incremental energy with patches (RR: 1.14, 95% CI 1.00 to 1.131) likely results in an increase in maintenance of sinus rhythm at hospital discharge or end of study follow-up (certainty of evidence: high). Use of AP BTE incremental with paddles (RR: 1.03, 95% CI 0.98 to 1.09; certainty of evidence: low) may lead to a slight increase, and AP MDS Incremental paddles (RR: 0.95, 95% CI 0.86 to 1.05; certainty of evidence: low) may lead to a slight decrease in efficacy. On the other hand, AP MDS incremental energy using patches (RR: 0.78, 95% CI 0.70 to 0.87), AA RBW incremental energy with patches (RR: 0.76, 95% CI 0.66 to 0.88), AP RBW incremental energy with patches (RR: 0.76, 95% CI 0.68 to 0.86), AA MDS incremental energy with patches (RR: 0.76, 95% CI 0.67 to 0.86) and AA MDS incremental energy with paddles (RR: 0.68, 95% CI 0.53 to 0.83) probably result in a decrease in this outcome when compared to AP BTE incremental energy with patches (certainty of evidence: moderate). The network for pharmacological cardioversion showed that bepridil (RR: 2.29, 95% CI 1.26 to 4.17) and quindine (RR: 1.53, (95% CI 1.01 to 2.32) probably result in a large increase in maintenance of sinus rhythm at hospital discharge or end of study follow-up when compared to amiodarone (certainty of evidence: moderate). Dofetilide (RR: 0.79, 95% CI 0.56 to 1.44), sotalol (RR: 0.89, 95% CI 0.67 to 1.18), propafenone (RR: 0.79, 95% CI 0.50 to 1.25) and pilsicainide (RR: 0.39, 95% CI 0.02 to 7.01) may result in a reduction in this outcome when compared to amiodarone, but the certainty of evidence is low. For atrial flutter (14 trials), a network could be created only for antiarrhythmic drugs. Using placebo as the common comparator, ibutilide (RR: 21.45, 95% CI 4.41 to 104.37), propafenone (RR: 7.15, 95% CI 1.27 to 40.10), dofetilide (RR: 6.43, 95% CI 1.38 to 29.91), and sotalol (RR: 6.39, 95% CI 1.03 to 39.78) probably result in a large increase in the maintenance of sinus rhythm at hospital discharge or end of study follow-up (certainty of evidence: moderate), and procainamide (RR: 4.29, 95% CI 0.63 to 29.03), flecainide (RR 3.57, 95% CI 0.24 to 52.30) and vernakalant (RR: 1.18, 95% CI 0.05 to 27.37) may result in a large increase in maintenance of sinus rhythm at hospital discharge or end of study follow-up (certainty of evidence: low). All tested electrical cardioversion strategies for atrial flutter had very high efficacy (97.9% to 100%). The rate of mortality (14 deaths) and stroke or systemic embolism (3 events) at 30 days was extremely low. Data on quality of life were scarce and of uncertain clinical significance. No information was available regarding heart failure readmissions. Data on duration of hospitalisation was scarce, of low quality, and could not be pooled.

AUTHORS' CONCLUSIONS

Despite the low quality of evidence, this systematic review provides important information on electrical and pharmacological strategies to help patients and physicians deal with AF and atrial flutter. In the assessment of the patient comorbidity profile, antiarrhythmic drug onset of action and side effect profile versus the need for a physician with experience in sedation, or anaesthetics support for electrical cardioversion are key aspects when choosing the cardioversion method.

Long-term amelioration of an early-onset familial atrial fibrillation model with AAV-mediated in vivo gene therapy

Atrial fibrillation (AF) is a common cardiac disease with high prevalence in the general population. Despite a mild manifestation at the onset stage, it causes serious consequences, including sudden death, when the disease progresses to the late stage. Most available treatments of AF focus on symptom management or alleviation, due to a lack of fundamental knowledge and the fact that considerable variations of AF exist. With the popularisation of the next-generation sequencing technology, several causal genetic factors, including MYL4, have been discovered to contribute to AF, giving hope to developing its gene therapies. In this study, we attempted to treat a previously established rat AF model, which carried Myl4E11K/E11K loss of function mutation, via overexpression of exogenous wild-type Myl4 by AAV9 vectors. Our results showed that delivery of Myl4 expressing AAV9 to postnatal rat models rescued the symptoms of AF, indicating the therapeutic potential that early gene therapy intervention can achieve long-term effects in treating cardiac arrhythmias caused by gene mutations.

In-silico drug trials for precision medicine in atrial fibrillation: From ionic mechanisms to electrocardiogram-based predictions in structurally-healthy human atria

Atrial fibrillation (AF) inducibility, sustainability and response to pharmacological treatment of individual patients are expected to be determined by their ionic current properties, especially in structurally-healthy atria. Mechanisms underlying AF and optimal cardioversion are however still unclear. In this study, in-silico drug trials were conducted using a population of human structurally-healthy atria models to 1) identify key ionic current properties determining AF inducibility, maintenance and pharmacological cardioversion, and 2) compare the prognostic value for predicting individual AF cardioversion of ionic current properties and electrocardiogram (ECG) metrics. In the population of structurally-healthy atria, 477 AF episodes were induced in ionic current profiles with both steep action potential duration (APD) restitution (eliciting APD alternans), and high excitability (enabling propagation at fast rates that transformed alternans into discordant). High excitability also favored 211 sustained AF episodes, so its decrease, through prolonged refractoriness, explained pharmacological cardioversion. In-silico trials over 200 AF episodes, 100 ionic profiles and 10 antiarrhythmic compounds were consistent with previous clinical trials, and identified optimal treatments for individual electrophysiological properties of the atria. Algorithms trained on 211 simulated AF episodes exhibited >70% accuracy in predictions of cardioversion for individual treatments using either ionic current profiles or ECG metrics. In structurally-healthy atria, AF inducibility and sustainability are enabled by discordant alternans, under high excitability and steep restitution conditions. Successful pharmacological cardioversion is predicted with 70% accuracy from either ionic or ECG properties, and it is optimal for treatments maximizing refractoriness (thus reducing excitability) for the given ionic current profile of the atria.

Antiarrhythmic Drug Therapy in the Treatment of Acute and Chronic Atrial Flutter

In the present article, we will focus on the pharmacologic treatment of atrial flutter aimed either at restoring/maintaining sinus rhythm or controlling the ventricular response during tachyarrhythmia. To provide a comprehensive description we will start discussing the electroanatomic substrate underlying the development of atrial flutter and the complex relationship with atrial fibrillation. We will then describe the available drugs for the treatment of atrial flutter on the bases of their electrophysiological effects and data from available clinical studies. We will conclude by discussing the general principles of rhythm and rate control treatment during atrial flutter.

OUP accepted manuscript

Rate and rhythm control are still considered equivalent strategies for symptom control using the Atrial Fibrillation Better Care algorithm recommended by the recent atrial fibrillation guideline. In acute situations or critically ill patients, a personalized approach should be used for rapid rhythm or rate control. Even though electrical cardioversion is generally indicated in haemodynamically unstable patients or for rapid effective rhythm control in critically ill patients, this is not always possible due to the high percentage of failure or relapses in such patients. Rate control remains the background therapy for all these patients, and often rapid rate control is mandatory. Short and rapid-onset-acting beta-blockers are the most suitable drugs for acute rate control. Esmolol was the classical example; however, landiolol a newer very selective beta-blocker, recently included in the European atrial fibrillation guideline, has a more favourable pharmacokinetic and pharmacodynamic profile with less haemodynamic interference and is better appropriate for critically ill patients.

Flecainide in Ventricular Arrhythmias: From Old Myths to New Perspectives

Flecainide is an IC antiarrhythmic drug (AAD) that received in 1984 Food and Drug Administration approval for the treatment of sustained ventricular tachycardia (VT) and subsequently for rhythm control of atrial fibrillation (AF). Currently, flecainide is mainly employed for sinus rhythm maintenance in AF and the treatment of idiopathic ventricular arrhythmias (IVA) in absence of ischaemic and structural heart disease on the basis of CAST data. Recent studies enrolling patients with different structural heart diseases demonstrated good effectiveness and safety profile of flecainide. The purpose of this review is to assess current evidence for appropriate and safe use of flecainide, 30 years after CAST data, in the light of new diagnostic and therapeutic tools in the field of ischaemic and non-ischaemic heart disease.

Flecainide How and When: A Practical Guide in Supraventricular Arrhythmias

Transcatheter ablation was increasingly and successfully used to treat symptomatic drug refractory patients affected by supraventricular arrhythmias. Antiarrhythmic drug treatment still plays a major role in patient management, alone or combined with non-pharmacological therapies. Flecainide is an IC antiarrhythmic drug approved in 1984 from the Food and Drug Administration for the suppression of sustained ventricular tachycardia and later for acute cardioversion of atrial fibrillation and for sinus rhythm maintenance. Currently, flecainide is mostly used for sinus rhythm maintenance in atrial fibrillation (AF) patients without structural cardiomyopathy although recent studies enrolling different patient populations have demonstrated a good effectiveness and safety profile. How should we interpret the results of the CAST after the latest evidence? Is it possible to expand the indications of flecainide, and therefore, its use? This review aims to highlight the main characteristics of flecainide, as well as its optimal clinical use, delineating drug indications and contraindications and appropriate monitoring, based on the most recent evidence.

Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option

Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.

Emergency Department Management of Recent-Onset Atrial Fibrillation

Atrial fibrillation (AF) is the most common tachyarrhythmia managed in the emergency department (ED). Visits to the ED for a presentation of AF have been increasing in recent years, with an admission rate that exceeds 60% in the United States and contributes substantially to health care costs. Recent-onset AF-defined as symptom onset less than 48 hr-is a common ED presentation for which rate control or acute electrical or pharmacological cardioversion may be appropriate treatment modalities depending on patient-specific circumstances. The focus of this review is to discuss the current recommendations regarding the management of recent-onset nonvalvular AF in the ED, discuss medication administration considerations, and identify implementation strategies in the ED to optimize throughput and reduce hospital admissions.

A Long-Term Cost-Effectiveness Analysis Comparing Radiofrequency Catheter Ablation with Antiarrhythmic Drugs in Treatment of Chinese Patients with Atrial Fibrillation

INTRODUCTION

Radiofrequency catheter ablation (RFCA) is widely used to treat atrial fibrillation (AF) in China.

OBJECTIVE

We aimed to determine the long-term cost effectiveness of RFCA versus antiarrhythmic drugs (AADs) in treating AF from the perspective of third-party payers.

METHODS

The model was structured as a 12-month decision tree leading to a Markov model that simulated the follow-up treatment outcomes and costs with time horizons of 8, 15, and 20 years. Comparators were standard-of-care AADs. Clinical parameters captured normal sinus rhythm, AF, stroke, post-stroke, intracranial hemorrhage (ICH), gastrointestinal bleeding, post-ICH, and death. The risk of operative death, procedural complications, and adverse drug toxicity were also considered. The model output was quality-adjusted life-years (QALYs) and incremental cost per QALY gained.

RESULTS

RFCA incurred more costs than the AADs but resulted in more QALYs gained than did AADs. The incremental cost per QALY gained with RFCA versus AADs was ¥66,764, ¥36,280, and ¥29,359 at 8, 15, and 20 years, respectively. The sensitivity analyses showed that the results were most sensitive to the changes in RFCA cost and CHADS₂ score (clinical prediction rule for assessing the risk of stroke in patients with non-rheumatic AF).

CONCLUSION

Compared with AADs, RFCA significantly improves clinical outcomes and QALYs among patients with paroxysmal or persistent AF. From the Chinese payer's perspective, RFCA is a cost-effective therapy over long-term horizons.

Rhythm Control in AF: Have We Reached the Last Frontier?

AF is a worldwide epidemic, affecting approximately 33 million people, and its rising prevalence is expected to account for increasing clinical and public health costs. AF is associated with an increased risk of MI, heart failure, stroke, dementia, chronic kidney disease and mortality. Preserving sinus rhythm is essential for a better outcome. However, because of the inherent limits of both pharmacological and interventional methods, rhythm strategy management is reserved for symptom and quality-of-life improvement. While ‘classical’ antiarrhythmic drug therapy remains the first-line therapy for rhythm control, its efficacy and safety are limited by empirical use, proarrhythmic risk and organ toxicity. Ablative techniques have had an impressive development, but AF ablation still failed to demonstrate a significant impact on hard endpoints. Understanding of the complex mechanisms of AF will help to develop new vulnerable targets to therapy. Promising molecules are under development, intended to fill the gap between the current pharmacological treatment aimed at maintaining sinus rhythm and the expectations from rhythm strategy.

Comparative Pharmacokinetic and Electrocardiographic Effects of Intratracheal and Intravenous Administration of Flecainide in Anesthetized Pigs

We compared the pharmacokinetic (PK) profile and electrocardiographic (ECG) changes in response to intratracheal instillation of flecainide acetate into the left atrium and ventricle with intravenous (IV) flecainide acetate administration. In 12 closed-chest anesthetized Yorkshire pigs, we monitored the QRS complex and PR, JTc, and QTc intervals during sinus rhythm and correlated changes with venous plasma drug concentrations before and at 2, 5, 10, 15, and 30 minutes after drug administration. Intratracheal instillation of flecainide (0.75 and 1.5 mg/kg, rapid bolus) caused dose/concentration-dependent increases in the QRS complex duration of 10% and 19%, respectively, at 2 minutes, coinciding with peak venous plasma levels (1688 ± 177 and 2808 ± 217 ng/mL, respectively). IV infusion of flecainide (2 mg/kg) over 2 or 10 minutes similarly prolonged QRS complexes and PR intervals (both, P < 0.001). Intratracheal flecainide instillation increased PR interval briefly at 5 minutes. Neither intratracheal nor IV flecainide affected JTc or QTc intervals. Thus, the PK pattern of intratracheal instillation of flecainide is comparable to IV administration, although the absolute plasma concentrations were higher with IV infusion. Both modes of delivery elicited ECG changes that were consistent with the expected pharmacological activity of flecainide.

Antiarrhythmic Drug Therapy for Atrial Fibrillation

Atrial fibrillation (AF) is the most frequently encountered arrhythmia. Prevalence increases with advancing age and so as its associated comorbidities, like heart failure. Choice of pharmacologic therapy depends on whether the goal of treatment is maintaining sinus rhythm or tolerating AF with adequate control of ventricular rates. Antiarrhythmic therapy and conversion of AF into sinus rhythm comes with the side effect profile, and we should select best antiarrhythmic therapy, individualized to the patient. New antiarrhythmic drugs are being tested in clinical trials. Drugs that target remodeling and inflammation are being tested for their use as prevention of AF or as upstream therapy.

Surgical perspectives in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia and a huge public health burden associated with significant morbidity and mortality. For decades an increasing number of patients have undergone surgical treatment of AF, mainly during concomitant cardiac surgery. This has sparked a drive for conducting further studies and researching this field. With the cornerstone Cox-Maze III “cut and sew” procedure being technically challenging, the focus in current literature has turned towards less invasive techniques. The introduction of ablative devices has revolutionised the surgical management of AF, moving away from the traditional surgical lesions. The hybrid procedure, a combination of catheter and surgical ablation is another promising new technique aiming to improve outcomes. Despite the increasing number of studies looking at various aspects of the surgical management of AF, the literature would benefit from more uniformly conducted randomised control trials.

Narrow therapeutic index drugs: a clinical pharmacological consideration to flecainide

PURPOSE

The therapeutic index (TI) is the range of doses at which a medication is effective without unacceptable adverse events. Drugs with a narrow TI (NTIDs) have a narrow window between their effective doses and those at which they produce adverse toxic effects. Generic drugs may be substituted for brand-name drugs provided that they meet the recommended bioequivalence (BE) limits. However, an appropriate range of BE for NTIDs is essential to define due to the potential for ineffectiveness or adverse events. Flecainide is an antiarrhythmic agent that has the potential to be considered an NTID. This review aims to evaluate the literature surrounding guidelines on generic substitution for NTIDs and to evaluate the evidence for flecainide to be considered an NTID.

METHODS

A review of recommendations from various regulatory authorities regarding BE and NTIDs, and publications regarding the NTID characteristics of flecainide, was carried out.

RESULTS

Regulatory authorities generally recommend reduced BE limits for NTIDs. Some, but not all, regulatory authorities specify flecainide as an NTID. The literature review demonstrated that flecainide displays NTID characteristics including a steep drug dose-response relationship for safety and efficacy, a need for therapeutic drug monitoring of pharmacokinetic (PK) or pharmacodynamics measures and intra-subject variability in its PK properties.

CONCLUSIONS

There is much evidence for flecainide to be considered an NTID based on both preclinical and clinical data. A clear understanding of the potential of proarrhythmic effects or lack of efficacy, careful patient selection and regular monitoring are essential for the safe and rational administration of flecainide.

Systematic review and meta-analysis of surgical ablation for atrial fibrillation during mitral valve surgery

BACKGROUND

Surgical ablation has emerged as an acceptable treatment modality for patients with atrial fibrillation (AF) undertaking concomitant cardiac surgery. However, the efficacy of surgical ablation in patient populations undergoing mitral valve surgery is not well established. The present meta-analysis aims to establish the current randomized evidence on clinical outcomes of surgical ablation versus no ablative treatment in patients with AF undergoing mitral valve surgery.

METHODS

Electronic searches were performed using six databases from their inception to September 2013, identifying all relevant randomized controlled trials (RCTs) comparing surgical ablation versus no ablation in AF patients undergoing mitral valve surgery. Data were extracted and analyzed according to predefined clinical endpoints.

RESULTS

Nine relevant RCTs were identified for inclusion in the present analysis. The number of patients in sinus rhythm (SR) was significantly improved in the surgical ablation group compared to the non-ablation group at discharge. This effect on SR remained at all follow-up periods until >1 year. Results indicated that there was no significant difference between surgical ablation and no ablation in terms of 30-day mortality, all-cause mortality, pacemaker implantation, stroke, thromboembolism, cardiac tamponade, reoperation for bleeding and myocardial infarction.

CONCLUSIONS

Results from the present meta-analysis demonstrate that the addition of surgical ablation for AF leads to a significantly higher rate of sinus rhythm in mitral valve surgical patients, with no increase in the rates of mortality, pacemaker implantation, stroke and thromboembolism. Further research should be directed at correlating different surgical ablation subtypes to cardiac and cerebrovascular events at long-term follow-up.

MK-0448, a Specific Kv1.5 Inhibitor

Background—

We evaluated the viability of I Kur as a target for maintenance of sinus rhythm in patients with a history of atrial fibrillation through the testing of MK-0448, a novel I Kur inhibitor.

Methods and Results—

In vitro MK-0448 studies demonstrated strong inhibition of I Kur with minimal off-target activity. In vivo MK-0448 studies in normal anesthetized dogs demonstrated significant prolongation of the atrial refractory period compared with vehicle controls without affecting the ventricular refractory period. In studies of a conscious dog heart failure model, sustained atrial fibrillation was terminated with bolus intravenous MK-0448 doses of 0.03 and 0.1 mg/kg. These data led to a 2-part first-in-human study: Part I evaluated safety and pharmacokinetics, and part II was an invasive electrophysiological study in healthy subjects. MK-0448 was well-tolerated with mild adverse experiences, most commonly irritation at the injection site. During the electrophysiological study, ascending doses of MK-0448 were administered, but no increases in atrial or ventricular refractoriness were detected, despite achieving plasma concentrations in excess of 2 μmol/L. Follow-up studies in normal anesthetized dogs designed to assess the influence of autonomic tone demonstrated that prolongation of atrial refractoriness with MK-0448 was markedly attenuated in the presence of vagal nerve simulation, suggesting that the effects of I Kur blockade on atrial repolarization may be negated by enhanced parasympathetic neural tone.

Conclusions—

The contribution of I Kur to human atrial electrophysiology is less prominent than in preclinical models and therefore is likely to be of limited therapeutic value for the prevention of atrial fibrillation.

Atrial Fibrillation at an Internal Medicine Ward: Clinical and Prognostic Implications

Background: Little is known about atrial fibrillation (AF) appearing during hospitalization in an Internal Medicine ward. Purpose: We aimed to investigate characteristics and prognostic significance of in-hospital onset AF. Methods: We studied 249 consecutive unselected patients admitted to this medical department with paroxysmal or persistent AF (out-of-hospital group) or AF developed during hospitalization (in-hospital group). Demographic, clinical, laboratory, electrocardiographic and echocardiographic data and all-cause mortality following discharge were recorded and compared between the groups Results: Diabetes mellitus (p=0.05), renal dysfunction (p<0.001), chronic lung disease (p=0.03) and history of stroke (p=0.01) were found more common in the in-hospital group (56 patients), compared to the out-of-hospital group (193 patients). Patients from the in-hospital group were more likely to have recurrent episodes of AF during hospitalization (p=0.002), were more frequently treated with amiodarone (p<0.001), discharged in sinus rhythm (p=0.04) and with medications for rhythm control (p=0.04). Time from onset to termination of AF (p<0.001) and hospital stay (p<0.001) were longer in the in-hospital group. On a median of 39-months follow-up, survival rate was lower in the in-hospital vs. out-of-hospital group (69.6% vs. 81.3%, p=0.025). Older age was significantly associated with shorter survival in the in-hospital group [odds ratio (OR)=1.87, 95% confidence interval (CI) 1.15-3.03, p=0.009]. In the out-of-hospital group, advanced age (OR=2.17, 95%CI 1.51-3.10, p<0.001), no prior AF episode (OR=3.41, 95%CI 1.56-7.46, p=0.002), diabetes mellitus (OR=2.22, 95%CI 1.12-4.39, p=0.006) and renal dysfunction (OR=2.44, 95%CI 1.10-5.38, p=0.049) were significantly associated with shorter survival. Conclusion: Patients developing in-hospital AF differed from subjects hospitalized for AF with respect to the severity of the clinical profile and prognosis.

Safety of flecainide

Flecainide is a class Ic antiarrhythmic agent that has an important role as part of rhythm control strategies in patients with atrial fibrillation (AF). Early clinical data on the use of flecainide showed an increase in arrhythmias and mortality compared with placebo in patients with a previous myocardial infarction and asymptomatic or mildly symptomatic ventricular arrhythmias. These findings only apply to a specific group of patients with left ventricular dysfunction and ischaemic heart disease, but had a negative impact on the use of class Ic antiarrhythmics across all indications and patient groups. The aim of this review was to evaluate the available safety data for flecainide in the literature and to assess its current use in patients with AF. Current European guidelines now recommend the use of flecainide in carefully selected groups of patients with AF who do not have structural heart disease. This includes for the cardioversion of recent-onset AF, pretreatment prior to direct current cardioversion, out-of-hospital acute oral therapy ('pill-in-the-pocket' approach) and for the ongoing maintenance of sinus rhythm. Potential cardiac adverse effects of flecainide include proarrhythmia, conduction abnormalities and negative inotropic effects. Dizziness is the most frequent non-cardiac side effect, followed by blurred vision and difficulty focusing; these are almost all mild, transient and tolerable. Data from recent clinical trials in patients with supraventricular arrhythmias suggest that flecainide has a good tolerability profile in groups of appropriately selected patients. Caution is required when using flecainide in patients with renal dysfunction, and there are a number of drug interactions, but these are well documented and manageable. Overall, flecainide is a good choice for the pharmacological management of AF. It has a good safety record and low incidence of adverse effects, rare end-organ toxicity and a low risk of ventricular proarrhythmia. To ensure that the benefits of treatment outweigh any potential risks, careful patient selection and monitoring is required.

Antiarrhythmic drugs for atrial fibrillation

INTRODUCTION

Atrial fibrillation (AF) is associated with increased mortality and morbidity. Although stroke prevention is the only way to improve prognosis, antiarrhythmic drugs (AADs) are of primary importance both in the conversion to sinus rhythm and in the long-term control of rhythm and rate.

AREAS COVERED

We searched the Cochrane Library and Medline Database for articles published in English concerning efficacy and safety of AADs in AF. Particular attention was paid to the recently published European Society of Cardiology guidelines. This review provides an overview of the currently available drugs used in AF, with a particular emphasis on their comparative efficacy and safety in different kind of patients. Recent important findings, and advantages and disadvantages of recently approved drugs such as vernakalant and dronedarone, are also discussed.

EXPERT OPINION

AADs remain fundamental in the acute and long-term management of AF, to control symptoms and to reduce the negative impact of the arrhythmia on QoL. The choice of a rate- over rhythm-control strategy should be individualized and based on accurate evaluation of patient medical history and symptoms. New agents will contribute to improve treatment efficacy together with the guarantee of better safety profiles.

Atrial fibrillation: pathophysiology and current therapy

Atrial fibrillation is a common cardiac arrhythmia with rapid and irregular atrial activity. Instead of uniformly contracting as one chamber, the atrial compartment fibrillates. Several studies have demonstrated that this arrhythmia contributes substantially to cardiac morbidity and mortality. The purpose of this review is to describe the pathophysiology and clinical management of this arrhythmia.

Pharmacologic Conversion of Atrial Fibrillation and Atrial Flutter

Atrial fibrillation and atrial flutter are common arrhythmias in everyday clinical settings. Pharmacologic cardioversion (CV) is a simple and widely used strategy for the treatment of these arrhythmias, and many drugs are currently available. The choice of drug is strongly influenced by the time elapsed from atrial fibrillation onset and by a patient's clinical subset. Electrical direct-current CV is the treatment of choice in long-lasting forms; nevertheless, some agents also show efficacy in this setting. In addition, promising results come from studies on the efficacy and safety of new antiarrhythmic drugs and from therapeutic approaches that reduce the need for hospitalization and improve quality of life.

Atrial fibrillation: adverse effects of "pill-in-the-pocket" treatment and propafenone-carvedilol interaction

Propafenone and carvedilol share a common hepatic metabolism involving the oxidative pathway (CYP2D6). Therefore, oral loading with propafenone (as "pill-in-the-pocket" treatment of recent-onset atrial fibrillation) in a patient on concurrent carvedilol treatment may lead to a pharmacokinetic interaction, with high plasma levels of propafenone and potential drug-related adverse effects. In clinical practice, in order to improve the safety of "pill-in-the-pocket" treatment, use of propafenone loading should, in our view, be discouraged in patients on concurrent treatment with carvedilol.

Comparison of antero-lateral versus antero-posterior electrode position for biphasic external cardioversion of atrial flutter

External cardioversion is an established and very important tool to terminate symptomatic atrial flutter. The superiority of the biphasic waveform has been demonstrated for atrial flutter, but whether electrode position affects the efficacy of cardioversion in this population is not known. The aim of this trial was to evaluate whether anterior-lateral (A-L) compared with anterior-posterior (A-P) electrode position improves cardioversion results. Of 130 screened patients, 96 (72 men, mean age 62 +/- 12 years) were included and randomly assigned to a cardioversion protocol with either A-L or A-P electrode position. In each group, 48 patients received sequential biphasic waveform shocks using a step-up protocol consisting of 50, 75, 100, 150, or 200 J. The mean energy (65 +/- 13 J for A-L vs 77 +/- 13 J for A-P, p = 0.001) and mean number of shocks (1.48 +/- 1.01 for A-L vs 1.96 +/- 1.00 for A-P, p = 0.001) required for successful cardioversion were significantly lower in the A-L group. The efficacy of the first shock with 50 J in the A-L electrode position (35 of 48 patients [73%]) was also highly significantly greater than the first shock with 50 J in the A-P electrode position (18 of 48 patients [36%]) (p = 0.001). In conclusion, the A-L electrode position increases efficacy and requires fewer energy and shocks in external electrical cardioversion of common atrial flutter. Therefore, A-L electrode positioning should be recommended for the external cardioversion of common atrial flutter.

Surgery for Lone Atrial Fibrillation: Present State-of-the-Art

For two decades, the cut-and-sew Cox-Maze III procedure was the gold standard for the surgical treatment of atrial fibrillation (AF), and proved to be effective at curing lone AF and preventing its most dreaded complication, stroke. However, this procedure was not widely adopted due to its complexity and technical difficulty. Over the last 5-10 years, the introduction of new ablation technology has led to the development of the Cox-Maze IV procedure, as well as, more limited lesion sets, with the ultimate goal of performing a minimally-invasive lesion set on the beating heart, without the need for cardiopulmonary bypass. This review summarizes the current state of the art and future directions in the surgical treatment of lone atrial fibrillation. The hope is that as we learn more about the mechanisms of AF and develop preoperative diagnostic technologies capable of precisely locating the areas responsible for AF, it will become possible to tailor specific lesion sets and ablation modalities to individual patients, making the surgical treatment of lone AF available to a larger population of patients.

Atrial fibrillation as a complication of dengue hemorrhagic fever: non-self-limiting manifestation

While electrocardiogram (ECG) changes are common during viral dengue infection, atrial fibrillation (AF) is a very rare manifestation. It has previously been highlighted that cardiac complications during dengue infection are invariably transient and will spontaneously resolve following recovery from the illness. We present the case of a young patient with IgM- and IgG-positive dengue hemorrhagic fever complicated by AF. ECG revealed a structurally normal heart. The patient remained in AF despite resolution of the illness. Reversion to normal sinus rhythm was achieved after loading of oral amiodarone.

A formula for the stratified selection of patients with paroxysmal atrial fibrillation in the emergency setting: a retrospective pilot study

BACKGROUND

Amiodarone is a commonly used medication in the treatment of atrial fibrillation (AF) of recent onset.

STUDY OBJECTIVES

The aim of the study was to identify a possible formula for selecting Emergency Department (ED) patients with paroxysmal AF who will spontaneously restore sinus rhythm (SR), successfully restore SR with the use of loading intravenous (i.v.) amiodarone, or require 24-h maintenance amiodarone infusion.

METHODS

This retrospective pilot study included 141 patients with recent-onset AF. Patients who did not restore SR spontaneously received i.v. amiodarone (5 mg/kg) within a period of 30 min. In case of no response, an additional dosage of 1000 mg of i.v. amiodarone was administered over a period of 24 h. Binary logistic regression models were used to determine the predictors of spontaneous conversion and the response to amiodarone administration.

RESULTS

The formula ([heart rate/systolic blood pressure] + 0.1 × number of past AF incidences) was chosen as the one with the highest combined sensitivity and specificity. This index identified the patients who spontaneously restored SR (cutoff point 1.31 with 78.6% sensitivity and 77.9% specificity), whereas for patients who responded to the loading i.v. amiodarone dose, the use of the index (cutoff point 1.24) exhibited 84.1% sensitivity and 75.3% specificity.

CONCLUSIONS

This formula may be a useful and reliable bedside diagnostic tool to identify AF patients most likely to spontaneously convert, or respond to loading amiodarone administration in the emergency setting. The use of this index also can assist in patient risk stratification.

Drug therapy for atrial fibrillation

Atrial fibrillation (AF) is the most frequently diagnosed arrhythmia. Prevalence increases with age, and the overall incidence is expected to increase as the population continues to age. Choice of pharmacologic therapy for atrial fibrillation depends on whether or not the goal of treatment is maintaining sinus rhythm or tolerating atrial fibrillation with adequate control of ventricular rates. New antiarrhythmic drugs are being tested in clinical trials. Drugs that target remodeling and inflammation are being tested for their use as prevention of AF or as adjunctive therapy.

Atrial fibrillation: challenges and opportunities

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice. There are many pharmacological and nonpharmacological options available for AF patients. There is, however, a great deal of dissatisfaction with the available treatments of this arrhythmia. Furthermore, AF management remains associated with many challenges that make the treatment of AF a vexing problem. The present overview discusses these challenges and explores the opportunities associated with them.

Surgical ablation of atrial fibrillation: the Columbia Presbyterian experience

BACKGROUND

The Maze III procedure is an effective surgical treatment for atrial fibrillation (AF). However, it is not widely applied due to its complexity, increased operative times, and the risk of bleeding. Various energy sources have been introduced to simplify the traditional "cut and sew" approach.

METHODS

This study involves patients undergoing surgical atrial fibrillation ablation (SAFA) at a single institution from 1999 to 2005. Type of concomitant procedures, preoperative clinical characteristics, and chronicity of AF were evaluated in overall patient population. Parameters including surgical approach, lesion pattern, and energy source used were collected intraoperatively. Clinical outcomes examined were postoperative rhythm success, stroke, early mortality, and long-term survival.

RESULTS

Three hundred thirty-nine patients were identified. Three hundred twenty-eight (96.8%) patients had associated cardiac disease and underwent concomitant procedures; 75.8% of patients had persistent AF. Energy sources used were microwave (49.8%), radiofrequency (42.2%), and laser (8.0%). In 41.9% of cases a pulmonary vein encircling lesion was the only lesion created. Combination lesion sets were performed in the remaining cases. Rhythm success rates at 3, 6, 12, and 24 months were 74.1%, 68.2%, 74.5%, and 71.1%, respectively. Patients who underwent surgical removal of left atrial appendage by means of stapling or simple excision had no early postoperative stroke. Early mortality was 4.9%. Postoperative survival rates at 1, 3, and 5 years were 89.6%, 83.1%, and 78.0%.

CONCLUSIONS

Surgical ablation of atrial fibrillation is a safe and effective procedure in restoring sinus rhythm with excellent postoperative survival rates. Further advancements in the field will eventually result in minimally invasive procedures with higher success rates.

Medical management of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained tachyarrhythmia encountered in clinical practice. The management of AF remains associated with many challenges that make its treatment a vexing problem. However, in recent years extraordinary progress has been made in the understanding and management of AF. In general, antiarrhythmic drugs for rhythm control have been disappointing. We have a better understanding of pharmacologic cardioversion and this has led to newer strategies, such as intermittent therapy. Several studies have been completed comparing pharmacologic rhythm control with pharmacologic heart rate control. There is also an emerging body of evidence concerning the value of adjunctive drug use for rhythm control using drugs that would not usually be considered to be antiarrhythmic. Finally, antithrombotic therapy is an increasingly important part of the medical management of AF. This article summarizes the results of many of the recent publications and their clinical implications concerning management of this common rhythm disorder.