Abstract
The prevalence of atrial fibrillation (AF) is forecasted to increase
manifold, emphasizing the need for efficacious treatments. Pulmonary
vein isolation (PVI) to eliminate ectopic triggers is now established as
a fundamental component of the invasive treatment of AF, however its
efficacy in persistent AF remains suboptimal. The atrial myocardium
undergoes adverse fibrotic remodeling as AF progresses, favoring
arrhythmia initiation and maintenance. Reductions in left atrial bipolar
voltage have been suggested to identify regions of such pathological
remodeling, and represent novel targets for ablation to target the
arrhythmogenic substrate. Early observational studies targeting these
low voltage areas (LVA) have been encouraging, however results from more
recent randomized trials are more mixed. Importantly, there is
significant heterogeneity in the techniques for identifying LVAs and the
strategies for ablation. In reality, the atrial arrhythmogenic substrate
is multi-faceted rather than being limited to fibrosis and there remains
uncertainty as to how accurately LVAs represent regions of fibrosis.
Additionally, bipolar voltage is influenced by numerous physiological
and biophysical factors.
The present review summarizes the current evidence for LVA ablation in
AF. We then analyze the components of the atrial arrhythmic substrate,
its relationship to LVAs and the limitations in LVA assessment. Finally
we discuss novel techniques for delineating the atrial substrate.
Keywords: Atrial fibrillation, substrate, ablation, voltage,
fibrosis