Elsevier

Heart, Lung and Circulation

Volume 26, Issue 9, September 2017, Pages 941-949
Heart, Lung and Circulation

Review
Radiofrequency Catheter Ablation For Atrial Fibrillation: Approaches And Outcomes

https://doi.org/10.1016/j.hlc.2017.05.125Get rights and content

Catheter ablation is now at the forefront of the management of symptomatic atrial fibrillation (AF). Its role in paroxysmal AF is well defined with considerable data supporting its role. Catheter ablation in persistent AF has been less effective and the subject of considerable debate. Mechanistic studies have demonstrated the critical role of pulmonary vein physiology in paroxysmal AF, whereas the mechanisms that sustain persistent AF are not well understood. Additional substrate ablation in persistent AF has not improved long-term outcomes and the use of novel mapping technologies to assess rotor activity remains controversial. This review will focus on the current understanding of the mechanistic basis of paroxysmal and persistent AF, the role of catheter ablation and, recent advances in the management of these complex arrhythmias.

Introduction

The focus of treatment in patients with atrial fibrillation (AF) centres on assessment and reduction of thromboembolic events by anti-coagulation and the treatment of symptoms. Anti-arrhythmic drug therapy had, for many years, been the cornerstone of therapy in paroxysmal AF. However, the long-term efficacy of medical management in this setting is sub-optimal and often unsatisfactory due to recurrent episodes of AF and side effects [1]. Over the last decade, catheter ablation has evolved into a routine procedure for selected patients with AF. This review will focus on recent advances in the understanding of the mechanistic basis of AF and the use of catheter ablation in its treatment.

Section snippets

Classification of AF

The nomenclature around AF also continues to evolve with the dominant classification being based upon arrhythmia duration and termination. Paroxysmal AF is defined as self-terminating episodes of AF lasting up to seven days. Persistent AF is present when an AF episode either lasts longer than seven days or requires termination by cardioversion with drugs or direct current cardioversion. Long-standing persistent AF is when AF is present for ≥1 year. Permanent AF is defined when a rate control

Medical Therapy for AF

Several randomised trials have failed to show the superiority of anti-arrhythmic medications over simple rate controlling medications in the treatment of AF in terms of mortality, stroke, hospitalisations and quality of life [2], [3], [4]. This has been attributed to an increase in mortality associated with the use of anti-arrhythmic agents [5].

Several randomised studies have shown that catheter ablation is superior to anti-arrhythmic medications in the reduction of symptoms, improved quality

Mechanistic Basis of AF

The last decade has seen significant progress in comprehending the molecular, cellular and electrophysiological basis of AF. Research has focussed on multiple domains, including the role of ion channel remodelling, oxidative stress, altered calcium handling, changes in atrial architecture and connexin expression in the pathogenesis of AF [12]. More recently, novel optical mapping techniques in ex vivo human hearts [13] and high density mapping [14], [15], [16] in patients has also added to our

Indications for AF Ablation

Given the ineffectiveness of medical therapy, the current HRS/EHRA/ECAS/APHRS/SOLAECE Expert Consensus Statement (in press) consider catheter ablation be reserved for patients with atrial fibrillation, which remains symptomatic despite optimal medical therapy, including rate and rhythm control [47]. Table 1 shows the class of consensus indications for catheter ablation for AF, modified from 2017 HRS/EHRA/ECAS/APHRS/SOLAECE Expert Consensus Statement.

Catheter Ablation in Paroxysmal AF

Given that the pulmonary veins are the source of foci initiating paroxysmal AF in 85–95% of patients, PV isolation (PVI) has become the cornerstone of all catheter based AF ablation strategies [48]. This empiric approach does not require detailed assessment of trigger sites, but targets the pulmonary vein antrum to achieve electrical isolation while minimising the risk of pulmonary vein stenosis and phrenic nerve injury. For all PVI techniques, ablation is performed until the endpoint of

Catheter Ablation in Persistent AF

The critical role of pulmonary vein physiology and anatomy has informed an ablation strategy with good long-term outcomes. However, in patients with persistent AF, especially those with long-standing (>12 months) AF, the mechanisms are much less clear. This has led to a wide variety of ablation strategies being published based on differing putative mechanisms. These have universally aimed to add further ablation beyond circumferential pulmonary vein isolation including linear ablation, ablation

Complications of AF Ablation

The published data on catheter ablation for AF report the risk of major complications in the range of 3.9% to 4.5% [77], [78]. These include death (in 1 of 1,000 patients), stroke, cardiac tamponade, atrio-oesophageal fistula, and clinically significant pulmonary vein stenosis. These studies reflect practice in a heterogeneous group of patients and varying ablation strategies between 1999 and 2007. Recent data has demonstrated that the safety profile of this procedure is best within high volume

Future Directions and Challenges

Enduring pulmonary vein isolation remains the major challenge in the setting of paroxysmal AF, with recurrences resulting from reconnections in the majority of cases. Catheters designed to measure tissue contact force have been developed to enable improved lesion creation with a number of studies demonstrating improved success and lower pulmonary vein reconnection [81], [82], [83], [84]. However, a recent multi-centre, randomised study supported previous reports that use of contact force did

Conclusion

Catheter ablation is now an established treatment for patients with symptomatic AF, resulting in significant improvements in quality of life [89]. Success rates in patients with paroxysmal AF and no significant structural heart disease can be in excess of 80%, although multiple procedures may be required. These outcomes are achieved with a very low incidence of complications in high volume centres with experienced operators. For patients with persistent AF, the role of catheter ablation

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