Local impedance to guide focal radiofrequency ablation: there is life in
the old dog yet
Despite being first described over 30 years ago, focal radiofrequency
(RF) continues to be the most widely used energy modality for catheter
ablation. The fact that it has managed to hold its own against stiff
competition from alternative energy sources used for pulmonary vein
isolation (PVI) is down to continuous evolution based on enhancements in
our understanding of its biophysical principles. In particular, the
advent of contact-force (CF) based integrated indices such as Ablation
Index have improved both efficacy and safety. However, a significant
limitation of this approach is the absence of tissue feedback during
lesion creation, which results in a blunt ‘one-size-fits-all’ approach.
This limitation has been further brought into focus by the recent
appreciation of the much greater importance of circuit impedance rather
than delivered power as a fundamental determinant of RF lesion size.