BACKGROUND: Impaired left ventricular (LV) ejection fraction is a common finding in patients with aortic stenosis and serves as a predictor of morbidity and mortality after transcatheter aortic valve replacement. However, conflicting data on the most accurate measure for LV function exist. We wanted to examine the impact of LV ejection fraction, mean pressure gradient, and stroke volume index on the outcome of patients treated by transcatheter aortic valve replacement. METHODS AND RESULTS: Patients treated by transcatheter aortic valve replacement were primarily separated into normal flow (NF; stroke volume index >35 mL/m) and low flow (LF; stroke volume index ≤35 mL/m). Afterwards, patients were divided into 5 groups: "NF-high gradient," "NF-low gradient" (NF-LG), "LF-high gradient," "paradoxical LF-LG," and "classic LF-LG." The 3-year mortality was the primary end point. Of 1600 patients, 789 (49.3%) were diagnosed as having LF, which was characterized by a higher 30-day (=0.041) and 3-year (<0.001) mortality. LF was an independent predictor of all-cause (hazard ratio, 1.29; 95% confidence interval, 1.03-1.62; =0.03) and cardiovascular (hazard ratio, 1.37; 95% confidence interval, 1.06-1.77; =0.016) mortality. Neither mean pressure gradient nor LV ejection fraction was an independent predictor of mortality. Patients with paradoxical LF-LG (35.0%), classic LF-LG (35.1%) and LF-high gradient (38.1%) had higher all-cause mortality at 3 years compared with NF-high gradient (24.8%) and NF-LG (27.9%) (=0.001). However, surviving patients showed a similar improvement in symptoms regardless of aortic stenosis entity. CONCLUSIONS: LF is a common finding within the aortic stenosis population and, in contrast to LV ejection fraction or mean pressure gradient, an independent predictor of all-cause and cardiovascular mortality. Despite increased long-term mortality, high procedural success and excellent functional improvement support transcatheter aortic valve replacement in patients with LF severe aortic stenosis.