Abstract： Objectives Left ventricular systolic dyssynchrony is the most important determinant of response to cardiac resynchronization therapy (CRT), playing a vital role to predict improvement of systolic function or LV reverse remodeling. CardioGRAF is a novel programmer based on the ECG gated single photon emission computed tomography (G-SPECT) imaging to detect LV systolic and diastolic dyssynchrony simultaneously. This study was to investigate the prevalence of systolic and diastolic left ventricular (LV) dyssynchrony in patients with heart failure. Methods We retrospectively studied 69 patients with heart disease, including 31 patients who had symptoms of heart failure (NYHA class Ⅱ-Ⅲ), and 38 patients who had no symptoms of heart failure (NYHA class Ⅰ). G-SPECT data were analyzed by cardiaGRAF, and measurements included the time to end systole (TES), the time to peak ejection (TPE), the time to peak filling (TPF), TES+TPF and maximal difference (MD) of each parameters were obtained, using the 95th percentile of the control group as a cutoffof 150 ms for MD-TES, 139 ms for MD-TPE, 345 ms for MD-TPF and 315 ms for MD-TES+TPF. Results The prevalence of LV systolic dyssynchrony was significantly higher in heart failure patients with reduced LV ejection fraction (LVEF)<45% (72% for MD-TES; 64% for MD-TPE) compared with heart failure patients with preserved LVEF=45% (14% for both MD-TES and MD-TPE; P=0.002, P=0.005, respectively); The prevalence of MD-TES<150 ms was higher in NYHA class Ⅲ patients (64%) compared with NYHA class Ⅱ patients (27%, P=0.049). However, the prevalence of the LV diastolic dyssynchrony were high but not difference between NYHA class Ⅲ(47% for both MD-TPF and MD-TES+TPF) and class Ⅲ(63% for MD-TPF; 69% for MD-TES+TPF; P=NS) patients as well as between patients with preserved LVEF (43% for both MD-TPF and MD-TES+TPF) and patients with reduced LVEF(64% for MD-TPF; 72% for MD-TES+TPF; P=NS). Conclusions The prevalence of LV systolic dyssynchrony was high in heart failure patients with reduced LVEF. Diastolic dyssynchrony was common in patients with heart failure. CardioGRAF maybe a useful method to detect LV dyssynchrony.