Among patients with paroxysmal AF, numerous randomized studies have demonstrated the
efficacy of catheter ablation as compared with anti-arrhythmic therapy to prevent
arrhythmia recurrence. However, among patients with long-standing persistent AF the
efficacy of catheter ablation remains particularly poor, with long-term freedom from
Atrial Tachycardia AT/AF off anti-arrhythmic medications generally as low as 30% after
one procedure. Multiple catheter ablation procedures are usually required in
long-standing persistent AF to achieve arrhythmia suppression.
Although pulmonary vein isolation (PVI) has been the main focus of catheter ablation for
atrial fibrillation, as a lesion set it is insufficient for long-standing persistent AF.
Electrical isolation of the posterior wall has been proposed as an adjunctive lesion set
to PVI for patients with persistent and long-standing persistent AF. The left atrial
posterior wall has a common embryological origin with the pulmonary veins, and
differences in fiber orientation at the intersection of the pulmonary veins and the LA
posterior wall may contribute to localized re-entrant circuits and subsequent AF. In
addition, the posterior wall is a site of parasympathetic innervation that could act as a
non-pulmonary vein trigger for AF. Typically, posterior wall isolation (PWI) during
catheter ablation involves the creation of lines between the superior edge of the left-
and right-sided PVI lesion sets, as well as between the inferior edges of the left- and
right-sided lesion sets. Another approach involves the delivery of lesions throughout the
posterior wall to target any electrical activity.
Observational studies of PWI have suggested that it improves outcomes over PVI in
persistent AF. However, randomized trials of catheter ablation for PWI have not shown
clinical benefit over PVI. An important possible reason for the negative results of the
randomized trials is the difficulty achieving durable PWI. In fact, a recent clinical
trial of a hybrid epicardial/endocardial ablation to achieve PVI and PWI was compared
with a standard endocardial catheter ablation set of PVI and a roof line. The CONVERGE
clinical trial of 153 patients with persistent and long-standing persistent AF showed
significantly higher rate of AF burden reduction in the treatment group (74% versus 55%)
by 18 months. The durability of PWI through epicardial ablation may be a major reason for
the increased efficacy in the hybrid ablation group.
Left atrial posterior wall ablation is also supported by 2 important mechanistic
studies-1 surgical (HISTORIC-AF) and 1 catheter based (PersAFone). Like in CONVERGE,
HISTORIC-AF evaluated a 2-procedure strategy of a minimally invasive, thoracoscopic
epicardial RF tool to create a posterior box lesion isolating all PVs and the posterior
wall en bloc; followed 1 month later by catheter-based endocardial touch-up ablation of
residual conduction gaps. This multicenter, prospective, nonrandomized study of 100
patients (32% with PerAF, 68% with longstanding PerAF) used implantable loop recorders
(ILRs) for continuous ECG monitoring for AF recurrence, and nonetheless demonstrated an
excellent 1-year maintenance of sinus rhythm rate of 88%. In PersAFone, patients with
PerAF underwent PVI + PWI using the Farawave pulsed field ablation (PFA) catheter. While
this trial only included 25 patients, the trial was notable for a design which included
remapping at 3 months (demonstrating durable PWI in all patients) with any necessary
touch-up ablation performed. Following this, the one-year freedom from AF recurrence was
92±5.4%.
PFA for AF offers very promising efficacy for PVI, with ~96% durability of isolated veins
at 90-day remapping. Furthermore, studies of PFA for PVI have also shown an extremely low
risk of esophageal injury.
Together, these data support a PFA-based PVI+PWI strategy as a simple, safe, fast
approach to treat this troublesome population of long-standing PerAF patients.
Accordingly, the research team proposes a prospective study of PVI and PWI for patients
with longstanding PerAF, using PFA in order to minimize the risk of esophageal injury and
maximize the likelihood of durable catheter-based ablation lesions. The research team
seeks to obtain precise estimates of arrhythmia recurrence post-ablation through ILRs in
follow-up.