2.5 Real-Time Phase Mapping
To detect the distribution of the AF rotors, an online real-time phase mapping system (ExTRa Mapping) was used. This mapping system was based on 41 bipolar intra-atrial electrograms (including 9 virtual electrograms) recorded by a deflectable 20-pole spiral-shaped catheter with a diameter of 2.5 cm (Reflexion HDTM, Abbott). The contact was confirmed by the recorded electrograms, fluoroscopy, and 3D geometry. The distance between the mapping points and geometry surface created by the EnSite NavX was set at 5 mm. The data sampling was adopted if there was good contact in the areas where sufficient electrograms could be recorded from the vast majority of the electrodes. When sufficient electrograms were not detected, the sensing threshold was decreased from 0.03 mV to 0.01 mV. Based on the 5-second wave dynamics during AF, each phase map was automatically created. Non-passively activated areas (NPAs), in which rotational activations (AF rotors) were frequently observed, were automatically detected according to the value of the “non-passively activated ratio (%NP)” (the ratio of the non-passively activated period to the recording time).10 NPAs were determined as areas up to the top 7 highest %NP values, which were above 50% of the %NP value. Thus, the NPAs could be considered as the area where AF rotors could be frequently found. To evaluate the distribution of the NPAs, the region of the whole LA was divided into the following eight segments: PV antrum, roof, anterior, posterior, lateral, bottom, septum, and left atrial appendage (LAA) base segments.