Evolving Treatment Strategies for the Ablation of Chronic Atrial Fibrillation

Evolving Treatment Strategies for the Ablation of Chronic Atrial Fibrillation

Andrea Natale
US Cardiovascular Disease 2006
Published: March 2006
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Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with an increased risk of morbidity and mortality.Asubanalysis of the Atrial Fibrillation Follow-up nvestigation of Rhythm Management (AFFIRM) suggests that there is a significant urvival benefitin the maintenance of sinus rhythm (SR), if it can be chieved without the potential adverse effects associated with ntiarrhythmic drugs.1 The limitations associated with traditional AF herapies have fostered an interest in developing effective ablation strategies.


Over the past decade, catheter ablation has emerged as a potential cure for paroxysmal AF (PAF) and chronic AF (CAF). Currently, the two main strategies used for all AF ablation are pulmonary vein antrum isolation (PVAI)2 and circumferential pulmonary vein ablation (CPVA).3 In this article, the question of which of these two strategies is a better initial step for ablation of persistent and permanent forms of AF will be discussed, and the continuing evolution of adjuvant strategies in the quest to eradicate CAF will be explored.

Treatment Strategies for Chronic Atrial Fibrillation AblationIs Complete Pulmonary Vein Isolation Necessary?
Haissaguerre and colleagues reported that in 95% of AF patients, focal discharges were responsible for the initiation of AF originating in at least one PV sleeve.4–6 More recent studies suggest that the PVs play a role in the maintenance of AF.7–9 Strategies that electrically disconnect the PVs incarcerate these triggers, thus preventing their interaction with the atrial substrate and resulting in the conversion or termination of AF.
CPVA is reported to be effective in both PAF and CAF. The approach used for both PAF and CAF is the same. CPVA consists of creating a 3D reconstruction of the left atrium (LA), then widely encircling the PVs 1–2cm from their ostia. Additional linear lesions are placed at the posterior LA, roof, and mitral isthmus. This strategy assumes that the atrial tissue adjacent to the PVs is involved in the perpetuation of AF. CPVA is effective in 74% of patients with CAF at one-year follow-up (off antiarrhythmic drugs).10 While these success rates may appear relatively impressive, the real concern is that anatomically guided CPVA results in apparently coalescent but electrically incomplete lesions with residual conduction in 45–60% of the PVs, as shown by data from both our institution and Hocini and colleagues.11,12 Furthermore, at follow-up 20–24% of patients developed left atrial flutter.

PV isolation (PVI) is an effective treatment for most cases of PAF. The strategy used for PVI is identical in both PAF and CAF. Complete electrical PVI is the desired end-point, and is evidenced by the disappearance (entrance block) or dissociation (exit block) of PV potentials. This strategy assumes that the arrhythmogenic activity responsible for AF is confined within the PVs. However, despite isolation of the major trigger sources, 15% of patients with permanent AF and structural heart disease have further episodes of AF after multiple procedures, thus suggesting that there is a component in addition to PV focal discharges acting as the driver for AF in these CAF patients.13 Nevertheless, Haissaguerre and colleagues have shown that in cases of long-lasting persistent AF, PVs are one of three target ablation sites (coronary sinus and left atrial appendage being the other two) that have the greatest impact on the prolongation of AF cycle length, the conversion of AF to atrial tachycardia (AT), and the termination of focal ATs.14 Therefore, while solely isolating the PVs is certainly a ‘too minimal’ strategy for the treatment of CAF, it is still a necessary component of AF ablation in this subset of patients.

Over the past decade, this technique has evolved from focal PV ablation to PV ostial, and then to PVAI.15 The focus of AF ablation strategy has been to eliminate potential triggers of AF with additional substrate modification if necessary. At the Center for Atrial Fibrillation, PVAI is performed with the guidance of a circular mapping catheter and intracardiac echocardiography (ICE). Radiofrequency (RF) energy is delivered, targeting potentials on the portion of the circular mapping catheter that defines the PV antrum junction. In a stepwise fashion, the circular mapping catheter is moved to different locations along the PV antrum–LA junction, and further RF energy is applied until the entire PV antrum–LA junction is ablated and electrically isolated. Each ablation treatment has the end-point of local potential elimination; thus, the duration of energy application is not fixed and is dependent on the potentials being ablated. Further RF energy is applied to the posterior wall and the roof of the LA. The ablation of the roof should connect the superior portions of the left and right PV antrum (see Figure 1).12

Currently, the best imaging modality for defining the PV antra is either computed tomography (CT) or magnetic resonance imaging (MRI). However, these two modalities are limited because they are unable to generate realtime images. ICE can be used to precisely identify the true borders of the PV antrum, to provide realtime information on catheter location along the PV antrum–LA junction, to avoid complications, and to allow for optimal power delivery by using microbubbles as a gauge to guide energy titration. Such an approach gives a better chance of achieving transmural lesions.16

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