In adults with moderate or severe aortic stenosis (AS), valve replacement surgery is recommended when symptoms (ie, angina, syncope, or congestive heart failure) appear.1 In such patients, valve replacement surgery alleviates symptoms and improves survival, even in those with a depressed left ventricular ejection fraction (LVEF). Although a minority of patients with symptomatic AS have a reduced LVEF, these individuals present challenges in evaluation and management. Article p 1738 In the patient with AS and a depressed LVEF, the latter may be caused by inadequate compensatory LV hypertrophy (so-called afterload mismatch) in which myocyte function is normal but LVEF is low because of inadequate LV mass. In such an individual, symptomatic status and LVEF improve with valve replacement surgery because the operation eliminates the preexisting excessive LV afterload, thereby restoring the match between LV myocyte mass and afterload. Alternatively, a depressed LVEF may be caused by a superimposed and separate myocardial disease process such as cardiomyopathy, ischemia, or fibrosis in which myocyte function is abnormal. In these individuals, operative risk is increased, symptomatic status often does not improve, and LVEF remains depressed after valve replacement surgery. Several previously published studies in subjects with AS and depressed LVEF have attempted to identify variables that may help to differentiate patients with afterload mismatch from those whose depressed LVEF is due to a separate disease process. Carabello and colleagues2 found that individuals with severe AS, depressed LVEF, and a transvalvular pressure gradient >30 mm Hg were likely to survive valve replacement surgery and to manifest symptomatic improvement postoperatively. In contrast, those with severe AS, depressed LVEF, and a low (<30 mm Hg) transvalvular pressure gradient did not benefit from valve replacement surgery; of 4 such subjects, 3 died perioperatively, and the 1 survivor did …