AIMS: The present study sought to assess the effect of global left ventricular (LV) afterload on LV myocardial systolic function in patients with aortic stenosis (AS) and preserved LV ejection fraction. METHODS AND RESULTS: We prospectively examined the LV myocardial deformation (i.e. longitudinal, radial, and circumferential) by two-dimensional speckle tracking in 173 patients with asymptomatic severe AS. Thirty-eight patients (22%) had low flow as determined by a low stroke volume index (or=5 mmHg mL/m(2)). Systemic arterial compliance (P = 0.001), circumferential myocardial deformation (P = 0.024), and left atrial area index (P = 0.04) were independently associated with increased global LV load in multivariable analysis. Of note, LV ejection fraction was not identified as a determinant of low flow or increased afterload. CONCLUSION: In asymptomatic patients with severe AS, LV ejection fraction markedly underestimates the extent of myocardial systolic impairment. Intrinsic myocardial dysfunction is particularly common in patients with increased global LV afterload, and especially in the subset of patients with low-flow AS.