Contemporary reviewOutcomes of long-standing persistent atrial fibrillation ablation: A systematic review
Introduction
The success of catheter ablation in patients with paroxysmal atrial fibrillation (AF) is now well established.1 However, the limited clinical success when the same approaches are applied to patients with persistent or long-standing persistent AF2, 3 has led to the search for the ideal ablation strategy. The vast contrast in success suggests that the mechanisms underlying the maintenance of persistent AF are different from the mechanisms of their paroxysmal counterparts. These alternative mechanisms perhaps are partly related to the significant remodeling instilled by the arrhythmia on the atria in terms of its structural and electrophysiologic properties. Linear lesions and/or electrogram-guided atrial substrate modification, targeted at interrupting self-sustaining macroreentrant or microreentrant wavefronts or focal sources, have been variably incorporated into ablation treatment of persistent/long-standing persistent AF in an attempt to improve outcomes. This systematic literature review was performed in order to collate the efficacy and complications of current approaches to ablation of long-standing persistent AF.
Section snippets
Methodology for reviewing the literature
The English scientific literature in the PubMed database was searched using “atrial AND fibrillation AND ablation AND (persistent OR long-standing persistent OR chronic OR long-term OR long-standing)” in any region of the PubMed record through June 1, 2009. The journal Circulation: Arrhythmia and Electrophysiology was manually searched due to its limited indexing in PubMed. The resulting 1,286 abstracts were reviewed to ensure that a (1) long-standing persistent or (2) mixed
Evidence from randomized controlled trials
Four randomized controlled trials (level II evidence) examining various ablation approaches for long-standing persistent AF have been conducted recently.4, 5, 6, 7 Unfortunately, there is little overlap in the ablation approaches assessed by each study, so their data cannot be combined (Figure 2). With respect to the clinical endpoint of single-procedure, drug-free success, these studies showed for long-standing persistent AF that
- 1
PVAI is a superior approach compared to PVA alone.7
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Complex
Evidence for each strategy
Randomized controlled trials have answered some of the questions regarding ablation of long-standing persistent AF; however, the critical question of technique over debulking persists. We reviewed case series (level IV evidence) to further investigate the outcomes associated with the different AF ablation strategies not assessed in randomized comparisons.
Pulmonary vein isolation
In one of the initial descriptions of persistent AF ablation, Haissaguerre et al9 reported a 40% single-procedure, drug-free success rate at 11 months after ablation in a highly selected group of patients in whom high-frequency triggers observed following cardioversion of AF were targeted by PVI. However, this sample was not representative of a clinical long-standing persistent cohort, so the data were excluded from the summary.
Four studies have reported clinical success of PVI in “unselected”
Linear ablation
Linear ablation eliminates more atrial substrates and partially compartmentalizes the atria with the aim of preventing the formation of macroreentrant circuits that have been postulated to maintain AF. Such linear ablation is anchored to electrically inert structures and has included the roof line, mitral isthmus, anterior line, and isolation of the entire posterior left atrium.
Electrogram-based ablation
The clinical outcomes associated with the procedures discussed suggest that regions other than the pulmonary veins, PVA, and posterior wall may play a role in the maintenance of long-standing persistent AF. In contrast to linear ablation, where a predetermined linear lesion is created empirically without detailed consideration of the underlying atrial substrate, electrogram-guided substrate modification selectively targets atrial tissue dependent upon the electrogram characteristics at the
Stepwise ablation approach
The stepwise ablation approach is an integration of most of the aforementioned techniques in a bid to additively improve the success of persistent/long-standing persistent AF ablation. The stepwise approach requires several key ablation techniques, namely, PVI, linear ablation at the roof and mitral isthmus, electrogram-targeted ablation, and discretionary right atrial ablation (superior vena cava, intercaval, or cavo-tricuspid isthmus lines). Each region is targeted in sequence, with the
Safety associated with long-standing persistent AF ablation
Assessment of complications was not a primary aim of this review; hence, case reports were not included. This may lead to potential underestimation of very rare complications, such as atrio-esophageal fistula. Twenty-eight of the 32 studies reported periprocedural complications; however, six of these reported complications occurred in a mixed AF type cohort and are not summarized here. Complications are reported as a percentage of the total 1,690 patients (n = 22 studies) included in the safety
Limitations
Only two studies7, 26 in this review clearly stated that all of their patients had continuous AF for more than 12 months, which is the most recent classification of long-standing persistent AF.8 All studies that referred to their patient cohorts as chronic, persistent/long-standing persistent, or long-lasting persistent, but with enrollment criteria that deviated from the contemporary definition, were included. Although the inclusion of these studies allowed for a more stable estimate of the
Conclusion
This systematic review collates the success associated with long-standing persistent AF ablation summarizes randomized controlled trials, and provides an indirect comparison of case series having different baseline characteristics, treated using a variety of methodologies, and followed up with different intensities. The variation in ablation methodology reported in this review demonstrates that the optimal technique for long-standing persistent AF ablation is still the subject of robust debate
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Dr. Sanders has served on the advisory board of, and has received lecture fees and research funding from, St. Jude Medical, Bard Electrophysiology, and Biosense Webster. Drs. Brooks and Sanders are funded by the National Heart Foundation of Australia. Dr. Lau is supported by a postgraduate medical scholarship from the National Health and Medical Research Council of Australia, the Earl Bakken Electrophysiology Scholarship from the University of Adelaide, and a Kidney Health Australia Biomedical Research Scholarship.