Noninvasive assessment of valve area in patients with aortic stenosis

A noninvasive method for quantification of aortic orifice area in patients with aortic stenosis is presented and compared with cardiac catheterization data in 24 patients (mean age 67 years). A continuous wave 2 MHz Doppler ultrasound instrument was used to measure the maximal velocity of the aortic jet, and time-averaged pressure drop was obtained by planimetry from the maximal velocity spectral recording using a simplified Bernoulli equation. Left ventricular ejection time was also measured from the spectral recording. Stroke volume was determined with a carbon dioxide-rebreathing method. Noninvasively determined aortic valve areas showed a close correlation with those determined at cardiac catheterization, but mean pressure gradients measured noninvasively were slightly but significantly higher than those measured at catheterization, leading to an underestimation of valve areas with the noninvasive technique, especially when valve areas were large. Neglect of blood flow velocity in the left ventricular outflow tract and recovery of static pressure downstream from the aortic orifice contribute to the difference in the pressure measurements. All patients with a valve area less than 1 cm2 at catheterization, however, also had an area less than 1 cm2 at the noninvasive investigation. This noninvasive approach to the evaluation of the severity of aortic stenosis seems promising for routine clinical use.