Patients affected by aortic stenosis with severe systolic left ventricular dysfunction have a poor spontaneous prognosis. The results of valvular replacement are globally good, at the price of an acceptable operative mortality. The existence of surgical failure has however prompted much work aimed at better definition of prognostic factors and for proposing new methods of specifying surgical indications. In this article based on a review of the literature, we discuss the physiopathology of left ventricular dysfunction, predictive factors for operative risk and survival, and the elements to be taken into account in order to adjust therapeutic decisions in these severe cases.