Ventriculo-arterial pressure gradient: It is usually the peak to peak gradient which is measured from pressure tracing during cardiac catheterisation, while Doppler echocardiography measures the peak instantaneous gradient. The difference between the two can be quite significant in the presence of pressure recovery phenomenon in aortic stenosis. Even otherwise there will be a difference between the peak to peak gradient measured by cardiac catheterization and peak instantaneous gradient measured by Doppler echocardiography. But this difference is more in case of pressure recovery, where the lower pressure near the valve is due to the effect of the jet which causes a reduction in the lateral pressure. To get the recovered pressure (settled pressure), catheter has to be pulled back about 2 to 3 cm beyond the sino-tubular junction.
Mean pressure gradient can be assessed by planimetry from the ventricular and arterial pressure gradient. Mean gradient will be about two third of the peak to peak gradient.