To assess the ability of baseline clinical parameters and imaging modalities to predict short and long term left ventricular function and clinical outcome of subjects with impaired left ventricular function and / or low-gradient, severe aortic stenosis.~To assess the impact of aortic valve replacement as compared to medical therapy on clinical outcome of patients with impaired left ventricular function and / or low-gradient, severe aortic stenosis.~To assess possible impact of aortic annulus assessment using 3-dimensional imaging modalities on the assessment of AS severity and definition of low gradient severe aortic stenosis.
To assess the ability of baseline clinical parameters and imaging modalities to predict short and long term left ventricular function and clinical outcome of subjects with low-gradient, severe aortic stenosis.~To assess the impact of aortic valve replacement as compared to medical therapy on clinical outcome of patients with low-gradient, severe aortic stenosis.~To assess possible impact of aortic annulus assessment using 3-dimensional imaging modalities on the assessment of AS severity and definition of low gradient severe aortic stenosis.