[Evaluation by Doppler ultrasound of the severity of aortic stenoses. Application of the continuity equation].

In order to assess the validity of the continuity equation applied to doppler ultrasound in the evaluation of stenotic aortic valve areas, the authors have compared the results obtained in 24 patients examined by catheterization and doppler-echocardiography. In addition, 10 patients who underwent aortic dilatation also had both types of examination, which brings up to 34 the number of comparisons. In haemodynamics, the Gorlin formula was taken as reference for valve area measurement. The doppler-echocardiographic examination, performed 48 hours before, and sometimes after catheterization, recorded sub- and trans-stenotic pressures and outflow tract diameter for application of the continuity equation. Aortic valve areas calculated from doppler data on mean velocities correlated well with areas calculated from haemodynamic data (r = 0.88, p less than 0.001, e = 14 mm2, n = 34). Correlation was even closer when maximum velocities were used (r = 0.96, p less than 0.001, e = 8 mm2, n = 34). When only tight aortic stenoses with a less than 0.75 cm2 area were considered, the correlation remained very good (r = 0.87, p less than 0.001, e = 6 mm2, n = 34). This study therefore demonstrates the reliability of the continuity equation and of the simplified method using maximum sub- and trans-stenotic pressures without having recourse to planimetry. The accuracy of the method is dependent upon 3 parameters: 1. A maximum velocity jet must be obtained, which in turn depends on the investigator's experience and on the sensitivity of the equipment. 2. The velocity recorded by pulsed doppler ultrasound must be "representative" of flow in the outflow tract.(ABSTRACT TRUNCATED AT 250 WORDS)