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Background: At present, left ventricular ejection fraction (LVEF) is regarded as the main parameter of left ventricular (LV) function which impacts both therapeutic option and outcomes in patients with significant chronic aortic regurgitation (AR). More subtle abnormalities in LV systolic function may be detected before LVEF declines in these patients.Purpose. To assess parameters of LV mechanics by speckle-tracking echocardiography (STE) and their correlation with LVEF in patients with significant chronic AR.Methods. We prospectively studied 35 patients with moderate and severe chronic AR and 20 normal subjects. Exclusion criteria for AR patients were LVEF ≤50%, significant coronary artery disease, any LV wall motion abnormality, more than mild associated valvular heart disease, non-sinus rhythm. A comprehensive echocardiogram was performed in all subjects. Rotation was measured from two-dimensional greyscale LV parasternal basal and apical short-axis images by STE. LV twist was defined as the net difference in clockwise and counterclockwise rotation of LV apex and base. LVtor was calculated as the LV twist normalized to LV end-diastolic longitudinal length. Analysis of LV global longitudinal strain (GLS) by STE was performed on the four-chamber, two-chamber, and long-axis apical views, as previously described.Results. Age and gender of patients were similar in both groups. There was no difference in mean LVEF between groups (60±4% in AR group vs 62±3% in control group, p=0.15). Patients in the AR group had higher LV diameters and volumes, LV mass (p<0.01 for all), lower LV shortening fraction (LVSF) (p=0.007) and S wave velocity at septal site by TDI (p=0.009). Peak apical rotation was reduced in the AR group (12.6±8.0° vs 18.4±6.3°, p<0.001), while peak basal rotation was similar in both groups (-4.8±3.4° vs -5.6±2.6°, p=0.34). LVtor was lower in the AR group (1.9±0.8°/cm vs 2.9±0.8°/cm, p<0.001), and so was time to peak LV twist (p<0.001). GLS was lower in AR patients (-17.5±2.3% vs -20.1±3.0%, p=0.003). In AR patients, LVEF correlated significantly with LVFS (r=0.54, p=0.001), peak apical rotation (r=0.65, p<0.001), LVtor (r=0.67, p<0.001) and GLS (r=-0.70, p<0.001). At multivariable analysis LVtor and GLS emerged as independent determinants of LVEF in AR patients (p=0.001 for both).Conclusions: LVtor and GLS, assessed by STE, are reduced in patients with significant AR and normal LVEF. Both emerged as independent determinants of LVEF. The possible role of these parameters to monitor patients with significant AR before LVEF declines remains to be studied.