A 2-part prospective study was performed to evaluate the clinical outcome of patients with hemodynamically confirmed asymptomatic valvular aortic stenosis (AS). During phase 1, linear regression analysis showed continuous wave Doppler to be highly accurate in predicting catheterization measured peak systolic aortic valve pressure gradients in 101 consecutive patients aged 36 to 83 years (mean 65 +/- 8) with symptomatic AS. During phase 2, 90 additional patients (51 asymptomatic and 39 symptomatic) with Doppler-derived peak systolic aortic valve gradients greater than or equal to 50 mm Hg (range 50 to 132 [mean 68 +/- 19]) were followed for 1 to 45 months. Both groups of patients in phase 2 had similar Doppler gradients and clinical and auscultatory evidence of moderate to severe AS at baseline. Asymptomatic patients were younger (p = 0.01), had higher ejection fractions (p = 0.001) and were less likely to have an electrocardiographic strain pattern (p = 0.01) and left atrial enlargement (p = 0.02). End-diastolic wall thickness, left ventricular cross-sectional myocardial area and estimated left ventricular mass were 18% (p = 0.0001), 20% (p = 0.0008), and 29% (p = 0.002) greater in symptomatic patients. During 17 +/- 9 months of follow-up, 21 asymptomatic patients (41%) became symptomatic. Dyspnea was the most common initial complaint, occurring 2.5 and 4.8 times more often than angina and syncope, respectively. Compared with the 39 symptomatic patients, the 51 asymptomatic patients had a lower cumulative life table incidence of death from any cause (p = 0.002), and from cardiac causes (p = 0.0001) including sudden death (p = 0.013).(ABSTRACT TRUNCATED AT 250 WORDS)