[Value and limitations of valve resistance in assessing prosthetic aortic valve function: clinical study using dobutamine stress doppler echocardiography].

Hemodynamic resistance may be a useful index for the severity of valvular aortic stenosis, but little is known about the utility of valve resistance in assessing the prosthetic aortic valve function. This study investigated whether valve resistance is useful in assessing prosthetic valve function in 13 patients with normally functioning CarboMedics prosthetic aortic valves. Transvalvular pressure gradient, effective orifice area and valve resistance derived from two-dimensional and Doppler echocardiography were calculated before and after dobutamine infusion. Dobutamine was infused incrementally (3-12 micrograms/kg/min) under echocardiographic imaging. Transvalvular pressure gradient (24 +/- 7-->53 +/- 18 mmHg, p < 0.01) and valve resistance (102 +/- 32-->140 +/- 57 dynes.sec.cm-5, p < 0.01) significantly increased after dobutamine infusion. However, effective orifice area did not increase significantly (1.1 +/- 0.5-->1.2 +/- 0.5 cm2). These findings indicate that transvalvular pressure gradient and valve resistance are flow-dependent and should be treated with caution when assessing prosthetic valve function.