Simplified Pulmonary Vein Isolation Using singLe Catheter and IntraCardiac Echocardiography: The Simple-ICE Study

I. Introduction. Ablation for paroxysmal atrial fibrillation (PAF) by means of pulmonary vein isolation (PVI) is the principal method for the treatment of PAF. In the majority of centers PVI is confirmed by recording PV potentials (PVP) from the circular catheter placed at the ostium of PV. However, this method of confirming PVI by demonstrating conduction block has been developed several years ago when techniques and operator skills in creating continuous and transmural radio-frequency (RF) lesions around PV was far from optimal. Nowadays, technical progress led to significant improvement in the quality of RF lesions thanks to the advent of ablation electrodes with contact force (CF) measurement and computation of ablation index which includes stability of electrode, impedance, CF and temperature measurements. In addition, implementation of so-called CLOSE protocol and paying attention to the contiguity of RF lesions further improved the outcome of ablation. Therefore, it may be speculated that the time has come to give up using circular electrode to confirm PVI, especially that another technique to confirm PVI has been available for a long time. This technique consists of pacing from ablation electrode from the line of RF applications or slightly inside this line to confirm lack of impulse conduction from PV to the left atrium (LA). In addition, lack of PV signals from the tip of ablation electrode further confirms PVI.

Another progress in AF ablation consists of the expanding usage of electro-anatomical systems (EAM) and reconstructing LA chamber which enables performing procedure with minimal fluoroscopy. In recent years, the usual approach consisted of reconstructing LA chamber using fast electro-anatomical (FAM) technique by means of dedicated circular diagnostic electrode or, more time consuming, ablation electrode [6]. Another approach consisted of pre-procedural LA imaging using computed tomography or cardiac magnetic resonance and merging this image with the electro-anatomical map. In addition, rotational angiography for LA visualization has been used. However, all these methods have several limitations and drawbacks such as radiation exposure, additional cost and creation of LA anatomy before rather than during the ablation procedure which may not be very accurate.

The only currently available technique which can visualize LA anatomy on-line, is intracardiac echocardiography (ICE). The CartoSound software provides fast and adequate delineation of the LA chamber. It has been shown that ICE-based LA reconstruction may slightly underestimate chamber dimensions whereas FAM overestimates LA size. Also, ICE images acquired directly from the LA may improve procedural accuracy. There is no doubt that training and experience in using ICE for LA reconstruction are essential for achieving good quality LA maps. Thus, it seems that ICE could replace all above mentioned techniques used for LA imaging.

Additionally, ICE has been used during AF ablation for (1) performing safe and adequately directed transseptal puncture, (2) assessment of electrode contact with cardiac tissue, (3) choosing right spot for RF applications and (4) early detection of complications. Therefore, it is very tempting to use ICE also for creating LA anatomy as this tool has already been used during ablation procedures in many centers. Such an approach might reduce costs associated with the usage of other imaging tools and possibly shorten procedural duration. In addition, ICE can be effectively used for the LA appendage (LAA) assessment for the presence of clots and, therefore, the usage of transesophageal echocardiography (TEE) may be abandoned, further reducing costs. The reduction in fluoroscopy time when using ICE is obvious and has been confirmed by numerous authors. Although ICE has so many advantages, it has not been routinely used in many laboratories because of the need for long training and high cost of a single-use ICE probe. However, with the reduction of costs of other equipment and procedure duration the ICE-based AF ablation may occur cost effective.

During AF ablation procedure a diagnostic catheter is usually introduced to the coronary sinus (CS). It serves for pacing and as an anatomical marker during transseptal puncture performed under fluoroscopic guidance. In many centers second diagnostic electrode is introduced to the His bundle area, also as an anatomical marker facilitating transseptal puncture. However, when using ICE, the CS and His catheters are not needed because the interatrial septum is elegantly visualized by ICE. Diagnostic catheters are also used for exclusion of other arrhythmias and for urgent pacing if bradycardia or asystole occur during ablation, however, this can be also accomplished by pacing from ablation catheter.