Quantification of pressure gradients across stenotic valves by Doppler ultrasound

Abstract

Two-dimensional echocardiography has proven very useful in assessing valvular heart disease, but the technique is limited in certain groups of patients and is unable to quantify a transvalvular pressure gradient. Advances in the Doppler ultrasound techniques have made it possible to noninvasively measure velocity of flow across a stenotic heart valve and to calculate the pressure gradient. A commercially available, continuous and pulse wave Doppler instrument was utilized to assess the transvalvular pressure gradient in patients with mitral and aortic stenosis and the transmitral pressure half-time to calculate mitra valve area. Thirty-five consecutive adult patients with suspected aortic stenosis and 30 adult patients with suspected mitral stenosis underwent Doppler ultrasound examination within 24 hours of cardiac catheterization. An adequate Doppler examination was obtained in 81% of the patients with aortic stenosis, with a correlation between the Doppler-derived transaortic gradient and the catheterization-derived gradient of 0.94. The Doppler-measured gradient accurately separated those patients with significant aortic stenosis (gradients of greater than 50 mm Hg) from those patients with noncritical aortic stenosis. Similarly, an adequate Doppler examination was obtained in 90% of the adult patients with mitral stenosis. There was also close correlation between the mitral valve area and mean pressure gradient measured by the Doppler technique and that obtained at the time of cardiac catheterization (r = 0.87 and 0.85, respectively). The Doppler technique proved to be useful in those patients who had also undergone prior mitral commissurotomy. This study confirms that the combined continuous pulse wave Doppler technique will serve as a valuable addition to the diagnostic capabilities offered by echocardiography.