Introduction
Radiofrequency (RF) catheter ablation (CA) is an established treatment
for several types of cardiac arrhythmias. [1]Creating sufficient lesion formation is crucial for successful ablation.
In contrast, excessive RF delivery can lead to steam pops or
perforations;[2] therefore, it is paramount to
energize without excess or deficiency.
Recently, contact force (CF) sensing catheters have become the standard
tools for RFCA,[3] [4]
[5] and CF parameter-integrated indices, such as the force-time
integral (FTI),[6] ablation index
(AI),[7] [8] and lesion size index (LSI)[9], have been reported as effective surrogate
parameters for sufficient lesion creation, especially in pulmonary vein
isolation (PVI) for atrial fibrillation (AF). However, these indices are
provided only from the ablation parameters and do not include the
characteristics of the local myocardial tissue.
Historically, generator impedance change has been used as a surrogate
marker of lesion creation by an RF
application;[10] however, since the absolute value
of the change is crude, it cannot be used as a definitive marker of
lesion formation. Recently, a local impedance (LI) detectable ablation
catheter (INTELLANAV MiFiâ„¢ OI, Boston Scientific, Maple Grove, MN, USA:
MiFi) was put on the market. This catheter has 3 microelectrodes
incorporated into the distal tip, and a more precise LI would be
detected with these microelectrodes. Since the LI would be changed by
tissue contact and temperature, this parameter allows us to speculate
about the CF and tissue temperature during the RF application[11]. In addition, both LI- and CF-sensing
ablation catheters (INTELLANAV STABLEPOINTâ„¢ Boston Scientific, Maple
Grove, MN, USA: STABLEPOINT) have recently become available, and they
will contribute to additional improvement in the quality of RFCA.
Several studies have suggested that LI decreases reflect tissue
denaturation by RF applications, and the degree of LI drop is correlated
with the lesion size. [12][13] [14] [15] However, although the LI
can be changed by changing the catheter contact angle to the tissue,
data on the effects of the catheter contact angle on LI parameters and
lesion size are scarce. Therefore, this study aimed to evaluate the
relationships among the catheter contact angles, LI parameters, and
lesion size with 2 different LI-sensing ablation catheters in a porcine
experimental study.