ABSTRACT
Introduction. When using Lesion Size index (LSI) to guide
catheter ablation, it is unclear what combination of power, contact
force and time would be preferable to use and what LSI target value to
aim for. This study aimed at identifying desirable ablation settings and
LSI targets by using tissue impedance drop as indicator of lesion
formation.
Methods. Consecutive patients, undergoing their first left
atrial (LA) catheter ablation for atrial fibrillation, with RF powers of
20, 30 and 40 W were enrolled. Tissue impedance, contact force (CF),
Force Time Integral (FTI) and LSI values were continuously recorded
during ablation and sampled at 100 Hz. Mean CF and Contact Force
Variability (CFV) were calculated for every lesion. The effect of RF
power, ablation time, CF and CFV on impedance drop and LSI were
assessed.
Results. A total of 3258 lesions were included in the analysis.
For any target LSI value, use of higher RF powers translated into
progressively higher impedance drops. The impact of lower CF and higher
CFV on impedance drop was more relevant when using lower powers. Target
LSI values corresponding to maximum impedance drop were identified
depending on RF power, mean CF and CFV used.
Conclusions. Even in the context of an LSI-guided ablation
strategy, use of lower or higher powers might lead to different lesion
sizes. Different LSI targets might be needed depending on the
combination of RF power, CF and CFV used for ablation. Incorporating
indicators of catheter stability, like CFV, in the LSI formula could
improve the predictive value of LSI for lesion size. Studies with
clinical outcomes are required to confirm the clinical relevance of
these findings.
Keywords: left atrial ablation, tissue impedance drop, Lesion
Size Index, high RF power, contact force, contact force variability.
Abbreviations: AF= atrial fibrillation; AI= Ablation Index; CF=
Contact Force; CFV= Contact Force Variability; FTI= Force Time Integral;
LA= Left atrium; LSI= Lesion Size Index; Max-Imp-∆= Maximum Absolute
Impedance Drop; Max-Imp-%= Maximum Percentage Impedance Drop; PVI=
Pulmonary Vein Isolation; PVs= Pulmonary Veins; RF= Radiofrequency
energy; SD= Standard Deviation; STL= Seasonal-Trend decomposition of
time series by Loess.