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.