Reproducibility of echocardiographic estimates of the area of stenosed aortic valves using the continuity equation.

Interobserver variability in echocardiographic estimates of the area of stenosed aortic valves was assessed in 30 consecutive patients. Using the continuity equation, two independent observers calculated the area of stenosis from separate recordings of the diameter of the aortic orifice and the velocity time integral in the left ventricular outflow tract and in the stenotic jet. No significant difference between the observers was noted for any measurement. With respect to the area of stenosis, a high correlation between the observers was found (r = 0.92, P less than 0.001) and the regression line was close to the line of identity. The 95% limits of agreement were less than +/- 0.3 cm2. No discrepancy between the observers was found in the assessment of cases for aortic stenosis less than 0.8 cm2. Regression analyses showed good interobserver agreement also for the diameter of the orifice, the velocity time integrals, and the mean pressure gradient (r greater than 0.90, P less than 0.001). The greatest variability was noted for the diameter of the aortic orifice (95% limits of agreement +/- 1.4 cm2). We conclude that echocardiography enables reproducible estimates of the orificial area of stenosed aortic valves. Changes greater than 0.3 cm2 can be detected with a confidence probability of 95%. The greatest source of error is the measurement of the diameter of the outflow tract at the basal attachments of the aortic leaflets.