Abstract: AIM: To assess left ventricular( LV) regional diastolic function in patients with hypertrophic cardiomyopathy( HCM) using single-beat real-time three-dimensional echocardiography( RT-3DE).METHODS: Seventy-six HCM patients( LV ejection fraction ≥45%) and 50 normal control subjects underwent examinations by two-dimensional echocardiography( 2DE) and RT-3DE. The parameters analyzed by RT-3DE included end diastolic sphericity index( EDSI),diastolic dyssynchrony index( DDI),dispersion end diastole DISPED,mean end diastolic time( MED),end systolic sphericity index( ESSI),systolic dyssynchrony index( SDI),dispersion end systole( DISPES),and mean end systolic time( MES). Patients were divided into three groups: impaired relaxation( n = 22),pseudonormal filling( n = 36),and restrictive filling( n = 18). RESULTS: In end diastole,DDI,DISPED and MED were abnormal in cases with severe diastolic dysfunction( 9. 95 ± 3. 75,41. 76 ± 17. 19,57. 82 ± 17. 07,respectively,P < 0. 01) and parameters increased with the severity of diastolic dysfunction. In end systole,SDI and DISPES also increased in cases of severe diastolic dysfunction( 8. 61 ± 2. 32,37. 29 ± 9. 67,respectively,P < 0. 01),but compared with those in control group,no significant difference were observed between mild and moderate diastolic dysfunction groups. There was a linear correlation between SDI and DDI. CONCLUSION: Dyssynchrony in systole shows a strong correlation with dyssynchrony in diastole in HCM. Systolic dyssynchrony could increase with the severity of diastolic dysfunction. Severe diastolic dysfunction may contribute to the systolic dyssynchrony.