From the apical 5 chamber view, the severity of aortic valve stenosis is best assessed utilizing pulse and continuous-wave Doppler to measure the peak instantaneous and mean pressure gradients across the aortic valve (which can be assumed to be an accurate measure of stenosis only if the valve is the only site of left sided obstruction and the left ventricular function and cardiac output are preserved). This is also a good view to assess for aortic regurgiation.
Transducer at cardiac apex
Notch at 3-4 o'clock (slight clockwise rotation)
4th or 5th intercostal space
Probe tilted anteriorly (tail down)
Aortic stenosis (quantification by spectral Doppler)