BACKGROUND: Echocardiographic measures of elevated left ventricular filling pressures are associated with an adverse prognosis. The aim of this study was to determine the relationship between acute (ratio of early transmitral flow to mitral annular velocity [E/e']) and chronic (indexed left atrial volume) markers of left ventricular filling pressure and mortality in patients with nonsevere aortic stenosis (AS), within the National Echo Database Australia cohort, testing the hypothesis that they would reflect the early hemodynamic consequences of AS and be associated with increased mortality in this setting. METHODS: The first record for patients ≥18 years of age showing hemodynamically significant but nonsevere (mild or moderate) AS (mean pressure gradient ≥ 10 to <40 mm Hg and aortic valve area > 1 cm) was analyzed. Baseline demographics and echocardiographic variables were compared with those among patients without AS (mean pressure gradient < 10 mm Hg). Mortality linkage data were available for all patients. RESULTS: Of 78,886 patients with aortic valve mean pressure gradients < 40 mm Hg and aortic valve areas > 1 cm, 13,768 (17%) were identified with nonsevere AS (aortic valve mean pressure gradient 10-40 mm Hg), of whom 57% were men (mean age, 73 ± 13.4 years) with a median follow-up of 3.4 years (interquartile range, 1.7-6.1 years). In unadjusted time-varying coefficient models, nonsevere AS and indexed left atrial volume > 34 mL/m (hazard ratio [HR], 2.29; 95% CI, 2.03-2.58), E/e' ratio > 14 (HR, 2.27; 95% CI, 2.08-2.49), left ventricular ejection fraction < 50% (HR, 2.82; 95% CI, 2.50-3.19), and tricuspid regurgitation peak velocity > 280 cm/sec (HR, 2.54; 95% CI, 2.30-2.80) were associated with increased mortality hazard at the time of echocardiography. All markers were significant when combined in a multivariate model. CONCLUSIONS: Indices of elevated left ventricular filling pressure are independently associated with death in patients with nonsevere AS. Risk stratification models incorporating these variables may identify patients at risk for complications, warranting closer surveillance and possibly earlier intervention.