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Is pressure recovery an important cause of "Doppler aortic stenosis" with no gradient at cardiac catheterisation?

The derivation of pressure data from Doppler ultrasound was first described by Holen et al in 1976.' Some 20 years later we remain obsessed by comparisons between pullback "gradient" at catheterisation and peak or mean pressure difference derived from Doppler echocardiography. It should now be well-known that the two are related, but different. The pull-back gradient does not exist physiologically because the peaks of the left ventricular and aortic pressure waves do not occur simultaneously. The Doppler-derived peak instantaneous gradient is usually higher than peak to peak gradient at catheterisation, often by about 20 mm Hg but with a range from 1 to 53 mm Hg.' Pressure recovery is an underappreciated cause of this discrepancy.