Previous computer simulation research suggested "Phase shift" that the position of spiral reentry could be changed by low energy electrical point stimulus at the spiral reentry center. But the mechanisms of phase shift was still unclear. The objectives of this research was optical mapping image analysis of phase shift phenomenon using "phase variance" method. The optical mapping system was constructed by high-speed video camera, fluorescent dye (main wavelength=520 [nm]), micro-electrodes, Langendorff-perfused rabbit heart specimen and optically recorded (1000 [fps], 512x512 [pixels]).Image data was image processed to phase variance map, and analyzed with distance and interval map. Previous mechanisms of phase shift was explained that pair annihilation of two phase singularity and switched to another one. But our research found the new phase shift mechanisms that was the same rotational direction phase singularity were fused together.
