Validation of instantaneous pressure gradients measured by continuous-wave Doppler in experimentally induced aortic stenosis.

The relation between catheter-measured and Doppler-derived aortic pressure gradients was examined in 8 open-chest dogs. A snare was placed around the proximal ascending aorta and adjusted to provide a wide range of gradient to left ventricular (LV) outflow. A continuous-wave Doppler transducer was placed above the level of the obstruction and angled to optimize the audio and spectral signals. Pressure tip transducer catheters recorded LV and ascending aortic pressures simultaneously with the Doppler signal. In 120 randomly selected sinus beats, Doppler-derived maximal gradient correlated well with maximal instantaneous catheter gradient from 4 to 179 mm Hg (r = 0.99). Mean gradients also were closely related (r = 0.98). For gradients above 100 mm Hg, the correlation remained good (r = 0.98), but for gradients below 50 mm Hg, the correlation was not as precise (r = 0.81). All 120 cycles were digitized at 10-ms intervals to examine the correspondence between the Doppler and catheter data throughout systole. For the 2,742 pairs of points so obtained, the correlation was excellent (r = 0.95). The close relation between Doppler-derived pressure gradient and that measured simultaneously by catheterization provides further validation of the use of continuous-wave Doppler in the assessment of aortic stenosis, not only at maximal gradient, but throughout the period of LV ejection.