Doppler echocardiographic assessment with the continuity equation of St. Jude Medical mechanical prostheses in the mitral valve position.

Evaluation of the St. Jude Medical (SJM) valve in the mitral position with Doppler echocardiography has usually involved the use of gradients across the valve and the application of the pressure half-time (PHT) method to derive a mitral valve area. The purpose of this study was, first, to determine the normal values of effective orifice areas for the SJM valve in the mitral position using the continuity equation, and second, to evaluate whether this parameter provides an improved assessment of valve function. Accordingly, Doppler echocardiography was performed in 40 patients within 6 weeks after valve replacement. All patients were clinically stable, without evidence of valvular dysfunction or aortic insufficiency. Valve size ranged from 23 to 33 mm and ventricular ejection fraction averaged 54 +/- 13%. Effective orifice area was derived by the continuity equation using stroke volume measured in the ventricular outflow tract, divided by the time-velocity integral of the SJM valve jet, and by PHT. Doppler-derived SJM valve mean gradient averaged 4 +/- 2 mm Hg. Effective area by the continuity equation averaged 1.82 +/- 0.36 cm2 (range 1.03 cm2 for a 23 mm valve to 2.63 cm2 for a 31 mm valve) and was smaller than by PHT (mean 3.10 +/- 0.65 cm2, p = 0.0001; range 1.38 to 4.78 cm2). Areas by both methods were smaller than the actual valve orifice area provided by the manufacturer (4.53 +/- 0.80 cm2, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)