It was recently suggested that valvular resistance, defined as the pressure gradient/flow rate ratio, may better depict the hemodynamic impairment in aortic stenosis than does valve area. The relation between aortic valve resistance and left ventricular mechanics was studied with Doppler echocardiography in 13 patients (mean age 85 years) with severe aortic stenosis who underwent percutaneous balloon valvuloplasty. The Doppler-estimated peak valvular resistance, defined as the ratio of peak transvalvular pressure gradient to peak valvular flow rate, decreased from 510 +/- 190 dynes.s.cm-5 before valvuloplasty to 300 +/- 110 dynes.s.cm-5 after the procedure (p = 0.0001). There was a close linear relation between valvular resistance measured at catheterization and Doppler-derived peak valvular resistance (r = 0.91). After valvuloplasty, left ventricular ejection fraction increased from 53 +/- 13% to 62 +/- 11% (p = 0.0001). The percent increase in ejection fraction was linearly related to the percent decrease in end-systolic wall stress (r = 0.56), which was in turn related to the percent decrease in peak valvular resistance (r = 0.75). No such linear relation existed between the percent changes in valve area and those in end-systolic wall stress. In conclusion, hemodynamic improvement after valvuloplasty is more closely related to changes in valvular resistance than to changes in valvular area. It is suggested that valvular resistance can be estimated accurately by Doppler echocardiography with use of a simple method and should be a primary consideration in assessing the hemodynamics of aortic stenosis.