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.