AHRQ Effective Health Care Program - Research Reviews

Comparative Effectiveness of Radiofrequency Catheter Ablation for Atrial Fibrillation
Final Research Review published 6 Jul 2009

Background
The Agency for Healthcare Research and Quality commissioned this report to review the evidence for the clinical effect and safety of radiofrequency (RF) catheter ablation for the management of atrial fibrillation (AF). AF is the most common sustained arrhythmia seen in clinical practice. Its prevalence increases with age, from 0.1 percent in people under 55 years to more than 9 percent by 80 years of age.

The heavy burden of AF creates a pressing need for novel approaches to management. In some patients, symptoms as well as the hemodynamic effects of the arrhythmia can be controlled if the ventricular response is adequately slowed by atrioventricular (AV) nodal blocking agents. In other patients, the lack of an atrial “kick,” or atrial contraction (which contributes up to 20 percent of the left ventricular volume at the end of diastole), as well as the irregularity of the ventricular response, results in symptoms and deleterious hemodynamic consequences. The appropriate treatment is, therefore, the restoration of normal sinus rhythm, which is performed electrically and/or chemically.

Several randomized controlled trials (RCTs) have compared the two strategies of rhythm control vs. rate control. Individually, these RCTs have failed to show that one strategy is superior to the other. When a meta-analysis of 5,239 patients with AF enrolled in RCTs of rhythm vs. rate control was performed, a strategy of rhythm control with anti-arrhythmic drugs (AADs) was associated with a worse outcome, including an increased risk of all-cause death and thromboembolic stroke.

However, it is well recognized that a rhythm-control strategy with AADs is not equivalent to maintenance of sinus rhythm. In other words, the worse prognosis associated with a rhythm-control strategy in the clinical trials is not the equivalent of a worse prognosis with sinus rhythm per se, and it should not be a cause to abandon novel strategies aimed at maintaining sinus rhythm. Moreover, restoring sinus rhythm may provide benefits beyond symptomatic relief. In the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Study, a rhythm-control strategy with AADs offered no survival advantage over a rate-control strategy. However, in an “on-treatment” analysis of the relationship of survival to cardiac rhythm and treatment as they changed over time, the presence of sinus rhythm was associated with a considerable reduction in the risk of death and AAD use was associated with increased mortality. The beneficial effects of maintaining sinus rhythm with AADs may be offset by their serious side effects, leading the AFFIRM investigators to conclude that maintaining sinus rhythm might be beneficial if it could be achieved effectively with fewer adverse effects. Catheter ablation for AF could be promising in that regard.

Catheter ablation for AF is based on the understanding that electrical activity emanating from the pulmonary veins (PVs) serves as a trigger for AF in many patients. Sleeves of atrial muscle fibers have been shown to extend from the left atrium into the PVs for 1 to 3 cm. In a proof-of-concept study in 1998, Haissaguerre and colleagues studied 45 patients with paroxysmal AF (PAF) refractory to drug therapy, in whom 94 percent of the points of AF origin were mapped to foci inside the PVs. They observed that elimination of local electrograms at these foci with RF energy rendered 62 percent of the patients free of AF recurrence over 8 months of followup. This observation formed the basis for future development of RF catheter ablation (RFA) for AF.

The initial strategy of RFA involved delivery of RF energy at the sites of earliest activation in a segmental fashion at the ostium of the PVs. After the recognition of PV stenosis as a complication, the lesion set was moved to a more antral position within the atrium. Some centers adopted this method of PV isolation (also known as segmental or focal pulmonary vein isolation), which is guided by a circular multipolar catheter placed in the PV. The endpoint of the procedure is electrical isolation of the PVs or dissociation of PV potentials from atrial potentials.

Pappone reported a variation of Haissaguerre’s initial technique known as wide area circumferential ablation (WACA), in which RF energy is delivered in a circumferential fashion around the ipsilateral veins. In this anatomic-based procedure, two encircling lesions are created. The endpoint of the procedure is an abatement of the voltage of the signal at the ablation site.

Additional lesion sets have been used in an attempt to ablate non-PV triggers of AF and also to target atrial areas thought to be responsible for maintenance of AF. These linear lesions are placed in different regions in the left atrium and may include the posterior left atrium, the roof of the left atrium, the interatrial septum, and the isthmus formed between the mitral annulus and the pulmonary vein/left atrial appendage. In another effort to identify and ablate substrate sites, areas of complex fractionated electrograms have also been targeted. The cavotricuspid isthmus, which is the substrate for the maintenance of atrial flutter, has been a target of ablation when atrial flutter has been documented as a clinical rhythm. On occasion, RFA of the cavotricuspid isthmus has been performed empirically, as atrial flutter could degenerate into AF.

At present, the Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation, put forth by the Heart Rhythm Society (HRS) and endorsed by several professional organizations, states that the foundation of most AF ablation procedures is to target the PVs and/or PV antrum. After discussion with a technical expert panel convened for this Comparative Effectiveness Review and in accordance with the HRS Consensus Statement, we reviewed only studies that included the targeting of the PVs or PV antrum, with or without the addition of other strategies.

The present review examines the evidence for the short- and long-term effect and safety of RF catheter ablation for AF.


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