The indices of evaluating left ventricular dyssynchrony on Gated-SPECT include: - PSD: OMC standard deviation of myocardial regions (more than 600 OMC) - HBW: interval containing 95% of OMC - HK, HS: Histogram Kurtosus and skewness 8 Assessment of left ventricular dyssynchrony - The control group had 4 indicators assessed with PSD, HBW, HK, and HS - From the mean of PSD and HBW of the control group, we take the threshold of > +2SD of the control group as the threshold of dyssynchrony.