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.