Importance of pressure recovery for the assessment of aortic stenosis by Doppler ultrasound - Role of aortic size, aortic valve area, and direction of the stenotic jet in vitro

Background Pressure recovery has been shown to occur distal to aortic stenoses in experimental and clinical studies. However, its clinical relevance in this setting has not yet been evaluated. Methods and Results To address the hypothesis that pressure recovery can cause significant differences between Doppler and catheter gradients in aortic stenosis and to examine the effects of aortic size, aortic valve area, and direction of the stenotic jet on these differences, stenoses with valve areas from 0.5 to 1.25 cm(2) and aortic diameters from 1.8 to 5.0 cm were studied in a pulsatile flow model. Jets entered the aorta centrally or eccentrically with angles of 15 degrees, 30 degrees, or 45 degrees. Overall, good correlation was found between Doppler and catheter gradients. However, when the various combinations of orifices and aortas were analyzed separately, slopes varied from 1.0 to 1.86, and the Doppler-catheter gradient differences ranged from -2 (small valve area with a large aorta) to 66 mm Hg (80% overestimation by Doppler echocardiography) when the stenosis was moderate and the aorta was small. Mild eccentricity of the jet did not significantly alter the results. However, overestimation by Doppler decreased with increasing jet eccentricity. Finally, differences between Doppler and catheter gradients could be predicted by estimating pressure recovery from Doppler measurements. Conclusions Significant pressure recovery can occur in aortic stenosis and can cause differences between Doppler and catheter gradients. These differences may reach clinical relevance, particularly when the stenosis is moderate and the aorta is small and can be predicted from Doppler measurements.