Effectiveness Study of Circumferential vs. Segmental Ablation in Paroxysmal Atrial Fibrillation

Overview

This is a PI-initiated study that aims to evaluate the efficacy of two different methods of paroxysmal atrial fibrillation (PAF) ablation. There are currently two strategies for PAF ablation that are routinely performed by electrophysiology clinicians: (1) circumferential pulmonary vein ablation (CPVA) and (2) segmental pulmonary vein isolation (SPVI). However, it is not known if one approach is better than the other. This randomized study will evaluate and compare the efficacy of CPVA versus SPVI in subjects undergoing ablation for paroxysmal atrial fibrillation only. Subjects will have a 50/50 chance of receiving either the CPVA or SPVI ablation method.

Despite more than a decade of clinical experience and investigation, the optimal approach to ablation of paroxysmal atrial fibrillation (PAF) still remains controversial. There are currently two strategies for ablation of PAF: (1) circumferential pulmonary vein ablation (CPVA) and (2) segmental pulmonary vein isolation (SPVI). There are advantages and disadvantages associated with each method. In the CPVA method (1), contiguous ablation lesions are created to encircle the two left and right pulmonary veins (PVs), guided by a three-dimensional (3D) electroanatomic mapping system (Carto, Biosense Webster, Inc. or ESI NavX, St. Jude, Inc.) with a 3D left atrial (LA) geometry created either by using the mapping catheter or by importing a pre-recorded 3D computed tomography (CT) image. In the SPVI method (2), electrical potentials recorded at the PV ostium, that represent myocardial connections between the LA and PVs, are ablated at the PV ostium or just proximal to the PV ostium in the PV antrum. In this approach, ablation is performed segmentally at multiple sites around the PV ostium or antrum, until mapping with a circular catheter demonstrates pulmonary vein isolation. The reported success rates for SPVI for prevention of recurrence of PAF range from 60-87% (2-4) with most recurrences associated with recovery of PV conduction. Therefore, the success of SPVI for treatment of PAF appears to be related to in large part to permanent elimination of the triggers of AF. In a retrospective study by Sawhney et al, overall 5-year outcome after SPVI for PAF was similar to that for short-term follow up less than or equal to 2 years. However, late recurrences after 2 years did occur (up to 22.5%) and repeat ablation was often required to maintain freedom from symptomatic PAF (5). Even though success rates for CPVA have been reported to be higher (up to 90%), most CPVA procedures previously reported included left atrial linear ablation (LALA), additional ablation lesions or lines connecting the mitral valve to the posterior pulmonary veins or along the roof of the left atrium. Thus the success of CPVA may be due in part to ablation of substantially larger amounts of atrial tissue (6-7). However, additional ablation (LALA) may cause potential pro-arrhythmic effects that lead to development of atypical left atrial flutter (8). Compared to SPVI, CPVA resulted in higher success rates and lower fluoroscopy time in one study by Arentz et al (9). However, that study included subjects with both PAF and persistent AF, and those with persistent AF have potentially different underlying mechanisms. Furthermore, two other randomized studies comparing the efficacy of PVI and CPVA have shown conflicting results (10-11). Thus, we will initiate this randomized controlled study to evaluate the efficacy of CPVA versus SPVI in subjects undergoing ablation of paroxysmal atrial fibrillation only.