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Purpose: When in patients with aortic stenosis (AS) left ventricle (LV) systolic dysfunction does occur, it may be reversible after valve replacement. Thus early detection of LV systolic dysfunction could be clue for surgery treatment. Therefore, we evaluated LV peak global longitudinal strain using speckle tracking imaging (ST) at rest and during low-dose dobutamine provocation in asymptomatic patients with moderate and severe AS and preserved LV ejection fraction (EF).Method: Peak global longitudinal 2D strain was measured from acquired apical 4ch and 2ch cine loops using EchoPac PC-workstation at rest and during 5, 10, and 20 μg/kg/min dobutamine provocation, respectively. The global strain was the average of the segment strains from the apical views. For each measurement, at least two cardiac cycles were averaged.The image acquisition frame rate was 60-90Hz, mean value 75Hz.Results: A total of 62 patients with moderate and severe AS (average aortic valve area (AVA) <=1.5cm2), mean age 66.12±9.91; (57.14% males), were enrolled in this prospective study. All patients underwent coronary angiography and had no obstructive coronary disease (defined as having no stenosis greater than 50% in diameter). At rest, average AVA was 0.83±0.23cm2, mean gradient (Pmean) was 43.57±0.29mmHg and mean EF was 72.24±0.45%. Peak global strain 4ch at rest was -10.4% with increase during maximal DS of 20 μg/kg/min to -11.5% and in 2ch view from -8.9% to -9.8%, p=ns. Heart rate was increasing in correlation with increasing dobutamine doses from 70±5.03 at rest to 84±13.2 at peak dobutamine, p=ns. In patients with severe AS (Pmean>40mmHg) global strain increased from -9.2±4.4% to -12±4.5% (p<0.05), while in patients with moderate AS global strain increased from -10.3±7.0% to -11.7±4.3%, p=ns.Conclusion: 2D strain speckle tracking analysis of myocardial deformation with measurement of peak systolic strain during dobutamine provocation is feasible and accurate method to determine myocardial systolic function and contractile reserve and may contribute to clinical decision making in management of patient with significant AS. However, decrease of LV systolic function in AS cannot be simply related to the severity of valve obstruction and needs to be evaluated in comparison with healthy control groups.