OBJECTIVES: We sought to assess predictors of mortality in consecutive patients with severe aortic stenosis undergoing aortic valve replacement and to determine whether there are differences in mortality, separated on the basis of different aortic stenosis subtypes and left ventricular stroke volume index. METHODS: We studied 875 patients (aged 69 ± 12 years, 67% were men) with severe aortic stenosis (aortic valve area ≤ 1 cm(2)) who underwent aortic valve replacement between January 2007 and December 2008 (excluding other severe valve disease, balloon aortic valvuloplasty, and transcatheter aortic valve replacement). Clinical and echocardiographic data were recorded. Left ventricular stroke volume index was measured as left ventricular outflow tract velocity time integral × left ventricular outflow tract area/body surface area. Patients were classified into the following subtypes: (1) standard severe (n = 536, left ventricular ejection fraction ≥ 50% and mean gradient ≥ 40 mm Hg); (2) paradoxic severe (n = 152, left ventricular ejection fraction ≥ 50%, mean gradient <40 mm Hg and left ventricular stroke volume index <35 mL/m(2)); and (3) low left ventricular ejection fraction severe (n = 187, ejection fraction <50%). Society of Thoracic Surgeons score and all-cause mortality were recorded. RESULTS: At 4.8 ± 2 years, 153 patients (18%) died (30-day mortality 1.8%). On multivariable Cox analysis, age (hazard ratio [HR], 1.49), New York Heart Association class (HR, 1.52), prior cardiac surgery (HR, 1.41), aortic stenosis subtypes (standard severe reference HR, 1; paradoxic severe HR, 1.48; and low left ventricular ejection fraction severe HR, 2.03), and reduced glomerular filtration rate (HR, 1.17) were associated with higher long-term mortality (P < .05). CONCLUSIONS: In patients with severe aortic stenosis undergoing aortic valve replacement, patients with standard severe aortic stenosis had better long-term survival than those with paradoxic severe or low left ventricular ejection fraction severe aortic stenosis.