Introduction
Pulmonary vein (PV) isolation is an essential procedure in catheter
ablation of atrial fibrillation (AF). However, reconnection of left
atrium to PV conduction is not rare, and is one of the main causes of AF
recurrence after PV isolation.1 Poor durability of PV
isolation arises from insufficient ablation lesions. Multiple factors
such as catheter-tissue contact, radiofrequency power, application time,
and tissue factors influence radiofrequency ablation lesion formation,
making it difficult to estimate the radiofrequency ablation lesion size.
Tissue impedance has been experimentally shown to decrease in heated
myocardium.2 A drop in generator impedance (GI)
between the catheter-tip and skin patch during radiofrequency
application (RFA) is used as a rough indicator of lesion
formation.3-5 However, the clinical utility of GI is
limited because it is a bulk impedance measurement that reflects the
electrical properties of not only the near-field myocardium but also
other thoracic structures such as skin, lungs, subcutaneous tissue, and
musculature.6
A novel ablation catheter (IntellaNav MiFi OITM;
Boston Scientific, Marlborough [Cambridge] MA, USA) that can measure
local impedance (LI) was recently launched. LI measures near-field
impedance, and may be a more specific representation of myocardial
impedance. The relationship between LI measurements and ablation lesion
formation were previously reported in an experimental
model6 and two clinical studies.7,8However, there is little data on the clinical utility of LI monitoring
during PV isolation.
The purpose of this study was to explore the clinical utility of LI
measurements for estimating ablation lesion formation during PV
isolation, and to clarify the target LI measurements at each RFA.