Pulmonary artery hypertension (PAH) increases mortality in patients with severe aortic stenosis. We hypothesized that left atrial (LA) dysfunction would be related to PAH in patients with severe aortic stenosis complicated by left ventricular (LV) systolic dysfunction. The data from 70 patients with severe aortic stenosis and LV systolic dysfunction were analyzed. From the transmitral flow, the peak early (E) and late (A) diastolic velocities were obtained. From the pulmonary vein flow, the peak S-wave, D-wave, and reversed atrial wave velocities were determined. The right ventricular systolic pressure was measured in 50 patients and averaged 38 +/-13 mm Hg. Patients with PAH (n = 19) presented with greater LV diameters, E/A ratio, E-wave velocity, LV mass index, reversed atrial wave velocity, and LA volume (p <0.05) and lower S/D ratio and total and active LA emptying fractions (p <0.05). Simple linear regression analysis revealed that the LA volumes and total and active LA emptying fractions displayed the strongest correlations with the right ventricular systolic pressure. Multiple regression analysis revealed that the minimum LA volume (r = 0.61, p = 0.0001) independently correlated with the right ventricular systolic pressure, irrespective of the aortic valve (AV) area or gradient. In patients who underwent an echocardiographic examination ≥1 month after AV replacement, LA function had improved significantly. The degree of improvement was related to the degree of recovery of the LV diastolic function and diameter. In conclusion, in patients with severe aortic stenosis and concomitant LV systolic dysfunction, the LA function parameters displayed the strongest correlations with the right ventricular systolic pressure, irrespective of the AV area or gradient and were impaired in patients with PAH. LA function recovered after AV replacement. Additional studies are warranted to determine the prognostic significance of LA function in this setting.