Atrial Fibrillation Structural Substrates: Aetiology, Identification and Implications

Atrial remodelling in AF underlines the electrical, structural and mechanical changes in the atria of patients with AF. Several risk factors for AF contribute to the development of the atrial substrate, with some evidence that atrial remodelling reversal is possible with targeted intervention. In this article, the authors review the electrophysiological changes that characterise the atrial substrate in patients with AF risk factors. They also discuss the pitfalls of mapping the atrial substrate and the implications for developing tailored ablation strategies to improve outcomes in patients with AF.

Relationship between CHA2DS2-VASc score and atrial electromechanical function in patients with paroxysmal atrial fibrillation: A pilot study

BACKGROUND

CHA2DS2-VASc score is the most widely preferred method for prediction of stroke risk in patients with atrial fibrillation. We hypothesized that CHA2DS2-VASc score may represent atrial remodeling status, and therefore echocardiographic evaluation of left atrial electromechanical remodeling can be used to identify patients with high risk.

METHODS

A total of 65 patients who had documented diagnosis of paroxysmal atrial fibrillation (PAF) were divided into three risk groups according to the CHA2DS2-VASc score: patients with low risk (score=0, group 1), with moderate risk (score=1, group 2), and with high risk score (score ≥2, group 3). We compared groups according to atrial electromechanical intervals and left atrium mechanical functions.

RESULTS

Atrial electromechanical intervals including inter-atrial and intra-atrial electromechanical delay were not different between groups. However, parameters reflecting atrial mechanical functions including LA phasic volumes (Vmax, Vmin and Vp) were significantly higher in groups 2 and 3 compared with group 1. Likewise, LA passive emptying volume (LATEV) in the groups 2 and 3 was significantly higher than low-risk group (14.12±8.13ml/m(2), 22.36±8.78ml/m(2), 22.89±7.23ml/m(2), p: 0.031). Univariate analysis demonstrated that Vmax, Vmin and Vp were significantly correlated with CHA2DS2-VASc score (r=0.428, r=0.456, r=0.451 and p<0.001). Also, LATEV (r=0.397, p=0.016) and LA active emptying volume (LAAEV) (r=0.281, p=0.023) were positively correlated with CHA2DS2-VASc score. In the ROC analysis, Vmin≥11ml/m(2) has the highest predictive value for CHA2DS2-VASc score ≥2 (88% sensitivity and 89% specificity; ROC area 0.88, p<0.001, CI [0.76-0.99]).

CONCLUSION

Echocardiographic evaluation of left atrial electromechanical function might represent a useful method to identify patients with high risk.

Target-specific oral anticoagulants in patients undergoing cardioversion

PURPOSE

Published evidence on the use of target-specific oral anticoagulants (TSOAs) versus traditional warfarin therapy in patients undergoing cardioversion for atrial fibrillation (AF) is reviewed.

SUMMARY

A literature search for published studies evaluating the TSOAs apixaban, dabigatran, and rivaroxaban as alternatives to warfarin for the prevention of thromboembolic events before and after cardioversion for AF identified a limited number of pertinent articles. Three of the four identified articles presented the results of retrospective analyses of data on TSOA use in relatively small cohorts of patients with AF who underwent cardioversion procedures during large clinical trials (RE-LY, ROCKET AF, and ARISTOTLE) that were not specifically designed to assess outcomes with TSOA use versus warfarin use. Those post hoc analyses did not indicate significant differences between groups of TSOA- and warfarin-treated patients in any of the clinical outcomes evaluated, including rates of stroke, systemic embolism, acute myocardial infarction, bleeding events, and 30-day and longer-term mortality. Anticipated reports on two trials of rivaroxaban (one recently completed and another scheduled for completion in 2014) are expected to provide additional insights on optimal strategies for anticoagulant prophylaxis in the context of AF cardioversion.

CONCLUSION

A limited body of published evidence suggests that dabigatran and apixaban may be effective alternatives to warfarin for anticoagulation therapy in patients with AF undergoing cardioversion. Careful consideration of the risks and benefits of TSOA versus warfarin use and patient preferences are key factors in appropriate drug selection.

Predictors of progression of recently diagnosed atrial fibrillation in REgistry on Cardiac Rhythm DisORDers Assessing the Control of Atrial Fibrillation (RecordAF)-United States cohort

The progression of atrial fibrillation (AF) to a more sustained form is associated with increased symptoms and morbidity. The aims of the REgistry on Cardiac Rhythm DisORDers Assessing the Control of Atrial Fibrillation (RecordAF)-United States (US) cohort study were to identify the risk factors of AF progression and the effects of management approaches. RecordAF is the first worldwide, 1-year observational study of the treatment of community-based patients with recent-onset AF. We assessed AF progression at 12 months in the US cohort. AF progression was defined as a change of AF to a more sustained form (either paroxysmal becoming persistent or permanent, or persistent becoming permanent). The US cohort included 955 patients, with mean age of 68.9 years; 56.8% were men and 88.8% were white. At entry, 59.6% of patients were selected for rate-control and 40.4% for rhythm-control therapy. At 12 months, the management strategy was unchanged for 68.2% of the patients in the rate- and 77.7% of the patients in the rhythm-control groups. Overall, AF progression had occurred in 18.6% of patients at 12 months. The progression rate was significantly greater in the rate-control (27.6%) than in the rhythm-control (5.8%) group (p <0.001). Progression to permanent AF occurred in 16.4% of patients. In addition to a rate-control strategy, older age, AF rhythm at entry, persistent AF at baseline, and a history of stroke or transient ischemic attack independently predicted AF progression. Rate control was associated with AF progression, with a propensity score adjusted odds ratio of 2.67 (p <0.001). In conclusion, rate control was the preferred treatment of recent-onset AF in the US but was associated with more AF progression than rhythm control.

Predicting atrial fibrillation inducibility in a canine model by multi-threshold spectra of the recurrence complex network

The purpose of this study is to predict atrial fibrillation (AF) from epicardial signals by investigating the recurrence property of atrial activity dynamic system before AF. A novel scheme is proposed to predict AF by using multi-threshold spectra of the recurrence complex network. Firstly, epicardial signals are transformed into the recurrence complex network to quantify structural properties of the recurrence in the phase space. Spectral parameters with multi-threshold are used to characterize the global structure of the network. Then the feature sequential forward searching algorithm and mutual information based Maximum Relevance Minimum Redundancy criterion are used to find the optimal feature set. Finally, a support vector machine is used to predict the occurrence of AF. This method is assessed on the pre-AF epicardial signals of canine which includes the normal group A (no further AF will happen), the mild group B (the following AF time is less than 180s) and the severe group C (the following AF time is more than 180s). 25 optimal features are selected out of 180 features from each sample. With these features, sensitivity, specificity and accuracy are 99.40%, 99.70% and 99.60%, respectively, which are the best among the recurrence based methods. The results suggest that the proposed method can predict AF accurately and thus can be prospectively used in the postoperative evaluation.

Pharmacological treatment of persistent atrial fibrillation in the older adult: evidence-based practice

PURPOSE

To answer the clinical question: In adults over 65 years of age with persistent atrial fibrillation (AF), do pharmacological rhythm-control agents offer a lower risk of stroke when compared to pharmacological rate-control agents? To address whether or not rhythm control improves quality of life compared to rate control was a secondary outcome question.

DATA SOURCES

Comprehensive review of pharmacological treatment of AF on stroke and quality of life outcomes; a meta-analysis of five randomized controlled trials.

CONCLUSIONS

Research suggests that all AF patients should continue anticoagulant therapy long term, even if they convert to sinus rhythm. Adequate rate control or rhythm control does not appear to reduce the need for lifelong antithrombotic therapy.

IMPLICATIONS FOR PRACTICE

While an individualized treatment approach to AF is essential, a strong focus in the care of the older adult with AF should be on maintaining therapeutic International Normalized Ratio (INR) levels. Improved quality of life is more dependent on reducing thromboembolic events and subsequent sequelae of stroke.

Post-ATHENA and beyond

Dronedarone, an amiodarone analog, was developed to be a safer alternative to amiodarone. Dronedarone is useful in suppressing atrial fibrillation/flutter and controlling the ventricular response. Dronedarone reduced cardiovascular hospitalization in the ATHENA trial (A placebo-controlled, double-blind, parallel arm Trial to assess the efficacy of dronedarone 400 mg bid for the prevention of cardiovascular Hospitalization or death from any cause in patiENts with Atrial fibrillation/atrial flutter). This paper reviews the results of ATHENA, including subsequent sub-analyses of the trial. These results raise the hypothesis that many of the benefits noted from this trial may be secondary to more than the antiarrhythmic properties of dronedarone. Future studies will clarify the mechanisms of this beneficial effect.

Management of atrial fibrillation: translating clinical trial data into clinical practice

Atrial fibrillation is a supraventricular tachyarrhythmia with significant consequences in terms of morbidity and mortality. In light of the limitations of available pharmacologic treatment options (suboptimal efficacy plus safety and tolerability issues), atrial fibrillation management should be individualized based on patient characteristics and comorbidities that could influence response to specific management approaches. The importance of adequate anticoagulation should not be overlooked. This review provides a practical guide for primary care physicians, internists, and cardiologists on current management strategies for atrial fibrillation, based on recent guidelines and current clinical data.

[Rate versus rhythm control with and without heart failure]

Atrial fibrillation and congestive heart failure are frequently associated with complex interactions. Patients with both diseases bear a sophisticated therapeutic challenge for the attending physician. The approach to treat atrial fibrillation differs for patients with and without heart failure in several aspects. Basic requirements are the treatment of the underlying diseases and prophylaxis of thromboembolic complications. Rate and rhythm control are the two main therapeutic strategies for atrial fibrillation according to the current guidelines. Large trials including the recently published AF-CHF study (Atrial Fibrillation - Congestive Heart Failure) failed to demonstrate a difference in mortality for both strategies. Thus, the therapeutic decision is mainly based on the patient's symptoms to improve quality of life. Rate control should be applied to asymptomatic patients or if rhythm control has already failed. If beta-blockers and digoxin have failed to control heart rate, His ablation with pacemaker implantation can be considered. In patients without heart disease, class I antiarrhythmic drugs and, in case of ineffectiveness, amiodarone or catheter ablation are recommended for rhythm control. First data concerning catheter ablation of atrial fibrillation in heart failure are promising and randomized studies are on the way. Rhythm control remains first-line therapy in recent-onset or highly symptomatic paroxysmal or persistent atrial fibrillation patients with and without heart failure.