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

Development and external validation of predictive models for prevalent and recurrent atrial fibrillation: a protocol for the analysis of the CATCH ME combined dataset

BACKGROUND

Atrial fibrillation (AF) is caused by different mechanisms but current treatment strategies do not target these mechanisms. Stratified therapy based on mechanistic drivers and biomarkers of AF have the potential to improve AF prevention and management outcomes. We will integrate mechanistic insights with known pathophysiological drivers of AF in models predicting recurrent AF and prevalent AF to test hypotheses related to AF mechanisms and response to rhythm control therapy.

METHODS

We will harmonise and combine baseline and outcome data from 12 studies collected by six centres from the United Kingdom, Germany, France, Spain, and the Netherlands which assess prevalent AF or recurrent AF. A Delphi process and statistical selection will be used to identify candidate clinical predictors. Prediction models will be developed in patients with AF for AF recurrence and AF-related outcomes, and in patients with or without AF at baseline for prevalent AF. Models will be used to test mechanistic hypotheses and investigate the predictive value of plasma biomarkers.

DISCUSSION

This retrospective, harmonised, individual patient data analysis will use information from 12 datasets collected in five European countries. It is envisioned that the outcome of this analysis would provide a greater understanding of the factors associated with recurrent and prevalent AF, potentially allowing development of stratified approaches to prevention and therapy management.

Predictors of sinus rhythm after electrical cardioversion of atrial fibrillation: results from a data mining project on the Flec-SL trial data set

Aims

Data mining is the computational process to obtain information from a data set and transform it for further use. Herein, through data mining with supportive statistical analyses, we identified and consolidated variables of the Flecainide Short-Long (Flec-SL-AFNET 3) trial dataset that are associated with the primary outcome of the trial, recurrence of persistent atrial fibrillation (AF) or death.

Methods and results

The 'Ranking Instances by Maximizing the Area under the ROC Curve' (RIMARC) algorithm was applied to build a classifier that can predict the primary outcome by using variables in the Flec-SL dataset. The primary outcome was time to persistent AF or death. The RIMARC algorithm calculated the predictive weights of each variable in the Flec-SL dataset for the primary outcome. Among the initial 21 parameters, 6 variables were identified by the RIMARC algorithm. In univariate Cox regression analysis of these variables, increased heart rate during AF and successful pharmacological conversion (PC) to sinus rhythm (SR) were found to be significant predictors. Multivariate Cox regression analysis revealed successful PC as the single relevant predictor of SR maintenance. The primary outcome risk was 3.14 times (95% CI:1.7-5.81) lower in those who had successful PC to SR than those who needed electrical cardioversion.

Conclusions

Pharmacological conversion of persistent AF with flecainide without the need for electrical cardioversion is a powerful and independent predictor of maintenance of SR. A strategy of flecainide pretreatment for 48 h prior to planned electrical cardioversion may be a useful planning of a strategy of long-term rhythm control.

[AFNET. A translational research network develops into an academic research organization]

"The whole is greater than the sum of its parts" (Aristotle).Atrial fibrillation (AF) is the most common sustained arrhythmia and affects 1-2 % of the population in developed countries, especially the elderly. We expect that the prevalence of AF will double in the next few decades. The last decades have seen important improvements in the management of atrial fibrillation, but many questions remain regarding the optimal diagnosis and management of the condition. The German Atrial Fibrillation NETwork (AFNET) was one of three cardiovascular competence networks in medicine funded by the German Ministry of Education and Research between 2003-2014. AFNET has contributed to the understanding of atrial fibrillation, and AFNET-led studies have led to improved clinical practices and practice guidelines in Germany and in Europe. This work has been expanded and is continuing in the AFNET association (AFNET e. V.). The AFNET association, founded in 2010 and continuing to this day, has developed into a small but fully formed academic research organisation that conducts investigator-initiated clinical trials as the responsible sponsor in Germany, Europe, and beyond. The AFNET association currently cooperates with EHRA (The European Heart Rhythm Association), ESC (The European Society of Cardiology) and DZHK (The German Centre for Cardiovascular Research) and receives funding from the European Union to generate evidence that can in the future lead to better prevention and management of AF.

Quality of life in patients with atrial fibrillation: how to assess it and how to improve it

Atrial fibrillation (AF) is the most frequent cardiac rhythm disorder and presents a considerable public health burden that is likely to increase in the next decades due to the ageing population. Current management strategies focus on the heart rate and rhythm control, thromboembolism prevention, and treatment of underlying diseases. The concept of quality of life (QoL) has gained significant importance in recent years as an outcome measure in AF studies evaluating therapeutic interventions and as a relevant component of a comprehensive treatment plan. Quality of life is impaired in the majority of patients with AF, and both rate and rhythm control strategies show significant improvement in QoL measures in highly symptomatic patients. This article reviews generic and specialized instruments for measuring QoL in the context of AF, discusses their applications and limitations to integration in clinical practice, and addresses the potential of early therapy for improving QoL outcomes. The development and validation of new QoL assessment tools will have a central role in the advancement of therapies and treatment guidelines for AF.

Short-term versus long-term antiarrhythmic drug treatment after cardioversion of atrial fibrillation (Flec-SL): a prospective, randomised, open-label, blinded endpoint assessment trial

BACKGROUND

Antiarrhythmic drugs prolong the atrial action potential and refractory period, and thereby prevent recurrent atrial fibrillation after cardioversion. The atrial action potential normalises after 2-4 weeks of sinus rhythm, suggesting that antiarrhythmic drugs might not be needed beyond that period. Therefore, we investigated whether short-term antiarrhythmic drug treatment after cardioversion is non-inferior to long-term treatment.

METHODS

We enrolled patients in a prospective, randomised, open-label, blinded endpoint assessment trial between May 4, 2007, and March 12, 2010, at 44 centres in Germany. Eligible patients were adults with persistent atrial fibrillation undergoing planned cardioversion. After successful cardioversion, patients were randomly assigned in permuted blocks of six per centre to: no antiarrhythmic drug treatment (control); treatment with flecainide (200-300 mg per day) for 4 weeks (short-term treatment); or flecainide for 6 months (long-term treatment). The primary endpoint was time to persistent atrial fibrillation or death. Patients and clinicians were unmasked to group assignment and treatment. The primary outcome was assessed in a core laboratory, members of which were masked to treatment group. Patients were monitored for 6 months by daily telemetric electrocardiograph (ECG) and centrally adjudicated Holter ECG recordings whenever atrial fibrillation was noted in two consecutive ECGs. Analyses were per protocol. This trial is registered, number ISRCTN62728742.

FINDINGS

After assay sensitivity was established with 4-week follow-up data from 242 patients showing that flecainide was superior to no treatment (Kaplan-Meier survival 70·2%vs 52·5%; p=0·0160), the trial continued to compare short-term versus long-term treatment. The primary outcome occurred in 120 (46%) of 261 patients receiving short-term treatment and in 103 (39%) of 263 patients receiving long-term treatment (event-free survival 48·4% [95% CI 41·9-55·0] vs 56·4% [49·1-63·6]; Kaplan-Meier estimate of difference 7·9% [-1·9 to 17·7]; p=0·2081 for non-inferiority; margin prespecified at 12%). In a post-hoc landmark analysis of patients who had not reached the primary endpoint in the first month, long-term treatment was superior to short-term treatment (Kaplan-Meier estimate of difference 14·3% [5·1-23·6]; hazard ratio 0·31 [0·18-0·56]; p=0·0001).

INTERPRETATION

Short-term antiarrhythmic drug treatment after cardioversion is less effective than is long-term treatment, but can prevent most recurrences of atrial fibrillation.

FUNDING

The German Federal Ministry of Education and Research, Deutsche Forschungsgemeinschaft, 3M Medica, and MEDA Pharmaceuticals.

What are the costs of atrial fibrillation?

The costs of atrial fibrillation (AF) are linked to the general cost of managing AF patients in different health-care systems, as well as the cost of managing AF-related complications (e.g. hospitalizations and long-term complications, such as stroke). In addition, indirect medical costs, such as care for patients who do not recuperate fully from a vascular event, and non-medical costs such as loss of work force add to the costs of AF. All estimations for cost of AF and cost of AF therapy are based on assumptions and markedly influenced by these cost determinants. This urges for extreme caution not to take cost estimates at their absolute values. In fact, even relative comparisons between interventions may have different consequences in terms of direct and indirect costs in different health-care settings. While newer therapeutic options appear to increase the cost of AF management, newer antithrombotic substances and adequate rhythm control therapy also carry the promise of preventing the two major drivers of AF-related cost, hospitalizations and AF-related complications. Formal assessment of the cost of AF requires adjustment to local practice, and more data are clearly needed especially from primary care to better estimate the 'real' cost impact of AF.

[The place of antiarrythmic drugs and rythm control in the treatment of atrial fibrillation]

Atrial fibrillation is the most commonly encountered arrhythmia in daily practice. Its incidence increases with age. It has been established that in this pathology there is self-aggravation with adverse electrical, functional, and structural remodeling of the atrial tissue. This remodeling can increase morbidity and mortality associated with atrial fibrillation. It has become increasingly clear that early checking of cardiac rhythm can stop this harmful remodeling. Several antiarrhythmia treatments have been demonstrated to be effective in cardioversion of arrhythmia and maintenance of the sinus rhythm. The therapeutic strategy depends on the degree of structural damage. Therapeutic trials and treatment selection take into account any possible cardiac side effects of the medications. The class IC antiarrhythmic agents are medications whose safety and efficacy have been demonstrated in patients with no underlying heart conditions. This article explores the advantages of maintaining the sinus rhythm using arrhythmics and the practical strategy of the pharmacological approach.

Can we improve outcomes in AF patients by early therapy?

Atrial fibrillation affects at least 1% of the population and causes marked society-wide morbidity and mortality. Current management of atrial fibrillation including antithrombotic therapy and management of concomitant conditions in all patients, rate control therapy in most patients, and rhythm control therapy in patients with severe atrial fibrillation-related symptoms can alleviate atrial fibrillation-related symptoms but can neither effectively prevent recurrent atrial fibrillation nor suppress atrial fibrillation-related complications. Hence, there is a need for better therapy of atrial fibrillation. The etiology of atrial fibrillation is complex. Most of the causes of atrial fibrillation which are known at present perpetuate themselves in vicious circles, and presence of the arrhythmia by itself causes marked damage of atrial myocardium. These pathophysiological insights suggest that early diagnosis and comprehensive therapy of atrial fibrillation, including adequate therapy of all atrial fibrillation-causing conditions, rate control, and rhythm control therapy, could help to prevent progression of atrial fibrillation and reduce atrial fibrillation-related complications. Such a therapy should make use of safe and effective therapeutic modalities, some of which have become available recently or will become available in the near future. The hypothesis that early diagnosis and early, comprehensive therapy of atrial fibrillation can improve outcomes requires formal testing in controlled trials.

The German Competence Network on Atrial Fibrillation (AFNET)

The German Competence Network on Atrial Fibrillation (AFNET) is an interdisciplinary national research network funded by the Federal Ministry of Education and Research (BMBF) since 2003. The AFNET aims at improving treatment of atrial fibrillation (AF), the most frequent sustained arrhythmia of the heart. The AFNET has established a nationwide patient registry on manifestation, diagnostics, and therapy of AF in Germany. The data analyzed to date demonstrate that patients with AF are likely to have multiple comorbidities (hypertension, valvular heart disease, coronary artery disease, diabetes mellitus) and an advanced age. Regarding oral anticoagulation, guideline adherence is very high. Basic research has identified specific changes in atrial tissue during AF-induced remodeling providing the rationale for novel therapeutic interventions. Clinical trials are being carried out to optimize pharmacological and nonpharmacological treatments. The ANTIPAF trial is designed to prove that angiotensin II receptor blockers reduce the incidence of paroxysmal AF. The Flec-SL trial tests the efficacy of a short-term treatment with antiarrhythmic drugs after cardioversion. The Gap-AF trial investigates the impact of complete pulmonary vein (PV) isolation versus incomplete circumferential PV ablation on AF recurrences. The effect of preventive pacing on the recurrence of paroxysmal AF is studied in the BACE-PACE trial.

[Treatment of atrial fibrillation]

Atrial fibrillation is a common and in most patients recurrent arrhythmia. Atrial fibrillation can increase mortality and causes at times severe symptoms in affected patients. Timely initiation of sustained oral anticoagulation is indicated in patients with atrial fibrillation at risk for stroke to prevent thromboembolic complications. Patients at risk for stroke can be identified by clinical characteristics using validated score systems, e.g., the CHADS(2) score or the Framingham score. Drugs that slow AV nodal conduction can improve symptoms associated with high ventricular rate. Cardioversion can acutely terminate atrial fibrillation in almost all patients, but many patients suffer from recurrent atrial fibrillation. The prevention of arrhythmia recurrences ("rhythm control therapy") is indicated in patients with severe arrhythmia-related symptoms. Antiarrhythmic drugs can approximately double the maintenance rate of sinus rhythm. Other drugs that were not primarily developed as antiarrhythmic agents, e.g., ACE inhibitors, sartans, and possibly statins, can further improve maintenance of sinus rhythm in selected patient groups. Catheter-based isolation of the pulmonary veins is a recently developed intervention that can cure some forms of atrial fibrillation. It is likely that a multimodal therapeutic approach will in the future allow rhythm control therapy to become more effective.

New concepts for old drugs to maintain sinus rhythm in patients with atrial fibrillation

Atrial fibrillation (AF) is a chronic, often progressive disease. Despite the ongoing concerted effort to improve AF therapy, often there is no remedy for curing AF and preventing the deleterious effects of the arrhythmia on health. Antiarrhythmic drug therapy is likely to remain the mainstay of therapy for many patients in the foreseeable future. Available antiarrhythmic drugs are moderately effective, which is important for patients who respond, especially given the chronic and often progressive nature of the disease. This article describes emerging concepts under clinical evaluation that attempt to improve the safety of available antiarrhythmic drugs in the treatment of recurrent AF. Two concepts are reviewed: (1) combination of an antiarrhythmic drug with a calcium channel blocker to reduce proarrhythmic side effects, and (2) "intelligent" reduction of the duration of antiarrhythmic drug therapy targeted to periods of symptomatic or likely AF recurrence.

[Modern pharmacotherapy of supraventricular and ventricular cardiac arrhythmia. An update for conventional therapy]

Currently the pharmacological approach still represents the mainstay in the acute phase of arrhythmia management as well as in the chronic treatment phase of specific entities such as atrial fibrillation. However, non-pharmacological options have recently emerged as frequently used first-line tools for the treatment of various supraventricular and ventricular heart rhythm disturbances. Nevertheless, antiarrhythmic drug treatment is frequently used as a bridging or adjunctive therapy in conjunction with catheter ablation or implantable cardioverter defibrillators. Antiarrhythmic agents constitute a very heterogeneous group prone to various drug interactions and side-effects. Therefore, this article aims to summarise the most important facts and recent findings with regard to appropriate contemporary pharmacological therapy of atrial and ventricular arrhythmias in clinical practice.

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

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

Multiple flavonoid-binding sites within multidrug resistance protein MRP1

Recombinant nucleotide-binding domains (NBDs) from human multidrug resistance protein MRP1 were overexpressed in bacteria and purified to measure their direct interaction with high-affinity flavonoids, and to evaluate a potential correlation with inhibition of MRP1-mediated transport activity and reversion of cellular multidrug resistance. Among different classes of flavonoids, dehydrosilybin exhibited the highest affinity for both NBDs, the binding to N-terminal NBD1 being prevented by ATP. Dehydrosilybin increased vanadate-induced 8-N3-[alpha-32P]ADP trapping, indicating stimulation of ATPase activity. In contrast, dehydrosilybin strongly inhibited leukotriene C4 (LTC4) transport by membrane vesicles from MRP1-transfected cells, independently of reduced glutathione, and chemosensitized cell growth to vincristine. Hydrophobic C-isoprenylation of dehydrosilybin increased the binding affinity for NBD1, but outsite the ATP site, lowered the increase in vanadate-induced 8-N3-[alpha-32P]ADP trapping, weakened inhibition of LTC4 transport which became glutathione dependent, and induced some cross-resistance. The overall results indicate multiple binding sites for dehydrosilybin and its derivatives, on both cytosolic and transmembrane domains of MRP1.