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Detection Algorithm of Phase Singularity Using Phase Variance Analysis for Epicardial Optical Mapping Data

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Naoki Tomii, Masatoshi Yamazaki, Tatsuhiko Arafune, Haruo Honjo, Nitaro Shibata and Ichiro Sakuma, University of Tokyo, Nagoya University, Tokyo Denki University, Mitsui Building Clinic, Japan

Spiral wave is presumed to play a significant role in irregular cardiac rhythms such as ventricular tachycardia (VT), ventricular fibrillation (VF) and atrial fibrillation (AF). Detection and tracking of the spiral core are essential for understanding complex spiral wave dynamics. It has been demonstrated that the core of the spiral wave can be identified as a phase singularity (PS) in a phase map. Existing quantitative detection methods intend to detect the PS using convolutional operation in a phase map. However, because of a large number of false positives, those methods could not automatically and stably track the core of sustaining spiral reentry in optical mapping data.

We developed a new PS detection algorithm by quantifying the variance of phase values in a phase map. PS can be identified as a point with peak phase variance value. The proposed method detects PSs using local spatial phase variance instead of convolutional operation. In comparison with the conventional method, our method improved the precision of detecting a single sustaining spiral wave core from 73.1% to 99.8%. The precision of the proposed method for multiple PSs detections was also higher than the convolution methods.

The proposed quantitative analysis method improved the precision ant the stability of spiral wave core detection in cardiac optical mapping images. The proposed method is better than existing approaches to reveal the complex spiral wave dynamics in optical mapping images. The objective analysis method of a spiral wave is important for understanding the mechanisms and dynamics of serious heart arrhythmias.

Keywords: phase singularity, spiral reentry, cardiac optical mapping, arrhythmia

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