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  • Fig shows different PVCs observed before PVC


    Fig. 4 shows 2 different PVCs observed before (PVC 1) and after the application of radiofrequency carnosic acid (PVC 2) in patient 17. After ablation of PVC 1, a different PVC (PVC 2) with a slightly different QRS morphology from that of PVC 1 was observed. Fig. 5 shows the activation sequence of PVC 1 and the corresponding virtual unipolar electrogram morphology at Site A. The earliest ventricular activation of PVC 1 was observed at Site A; then, the activation spread centrifugally. Thus, virtual unipolar electrogram morphology at Site A showed a QS pattern. After application of radiofrequency energy to Site A, mapping of PVC 2 revealed that the earliest ventricular activation site was the same as that during PVC 1, but the subsequent activation sequence was changed (Fig. 6). Although the earliest ventricular activation site was the same, subsequent activation was partially blocked at the right side of the PVC origin, and thus, the activation spread to the superior, inferior, and leftward directions (Fig. 6, panel a). Then, the activation split into superior and inferior directions (Fig. 6, panel b) and finally, propagated to the remainder of the RVOT (Fig. 6, panels c and d). Therefore, the change in the QRS morphology was caused by a different activation sequence that was associated with the localized conduction block. After the origin of PVC 2 was identified, additional radiofrequency energy was applied to the earliest ventricular activation site (Site A) to eliminate PVC 2. A mean of 16±8 radiofrequency deliveries were applied in the 20 patients, with a clinical success of 95.0% (19 of 20 patients). The percentage of patients with multiple origins of RVOT arrhythmia was significantly higher than that of patients with single origin (15 patients: 75.0% vs 5 patients: 25.0%, P<0.01). None of the complications associated with catheter ablation were observed.
    Conflict of interest
    Introduction Catheter ablation has been demonstrated to be an effective therapy for scar-mediated reentrant ventricular tachycardia (VT) and is being used prophylactically in the management of patients at risk for recurrent VT [1,2]. Substrate-based approaches with electroanatomic mapping (EAM) systems are critically dependent on an accurate delineation of the infarct architecture, which is a function of the mapping density. However, substrate-based ablation procedures often require long procedural times because of extensive point-by-point mapping. A method to improve the mapping density for the identification of late potentials (LPs) over a larger myocardial area holds promise for facilitating and expediting VT ablation. Contact mapping of an infarction by using NavX has been systematically validated in the left ventricle (LV) [3]. One advantage of the system is that it allows for simultaneous data collection from all electrodes of any or all catheters, if desired. Therefore, it is possible to allow for a quicker acquisition of a larger number of points for scar delineation. Furthermore, a new feature of the new EnSite Velocity system called “OneMap” might expedite the baseline mapping since it allows for simultaneous recording of the electrophysiologic data while building the chamber geometry. Thus, it may be advantageous to use a multipolar catheter combined with the Velocity system in the ventricle for rapid mapping and to guide ablation. The purpose of this study was to investigate the clinical feasibility of using the multipolar EAM combined with a new software system for the ablation of scar-mediated VT.
    Discussion Multipolar catheter mapping combined with the Velocity system can be applicable regardless of the strategy used for scar-related VT ablation. Arrhythmogenic scar homogenization [13], or the elimination of areas of slow conduction guided by LPs, has been proposed as an endpoint for VT ablation [10]. In this study, LPs were identified during substrate mapping with the use of a multipolar catheter in 83% (13 of 16) of the patients. Combined epicardial and endocardial mapping with the use of a multipolar catheter may hold promise in assessing the presence of abnormal electrograms. Appropriate catheter contact is also indispensable for a successful ablation. We found that positioning the multipolar catheter with a large curve in the ventricle usually resulted in both endocardial and epicardial excellent contact. However, it was helpful to confirm the presence of an adequate contact between the multipolar catheter and the ventricular surface with fluoroscopy, the EAM geometry, and the quality of the local electrograms. By using this mapping method, the mapping density was increased in areas of suspected scarring, and the findings of LPs were specific for differentiating a scar from a low-voltage area due to poor contact. Additionally, the routine use of the Velocity software further decreased the procedure times for substrate mapping. This software allows for simultaneous geometry and electrogram data acquisition, forestalling the need for two-step redundant mapping methods with the older software.