Doppler echo evaluation of pulmonary venous-left atrial pressure gradients: human and numerical model studies

The simplified Bernoulli equation relates fluid convective energy derived f rom flow velocities to a pressure gradient and is commonly used in clinical echocardiography to determine pressure differences across stenotic orifice s. Its application to pulmonary venous flow has not been described in human s. Twelve patients undergoing cardiac surgery had simultaneous high-fidelit y pulmonary venous and left atrial pressure measurements and pulmonary veno us pulsed Doppler echocardiography performed. Convective gradients for the systolic (S), diastolic (D), and atrial reversal (AR) phases of pulmonary v enous flow were determined using the simplified Bernoulli equation and corr elated with measured actual pressure differences. A linear relationship was observed between the convective (y) and actual (x) pressure differences fo r the S (y = 0.23x + 0.0074, r = 0.82) and D (y = 0.22x + 0.092, r = 0.81) waves, but not for the AR wave (y = 0.030x + 0.13, r = 0.10). Numerical mod eling resulted in similar slopes for the S (y = 0.200x - 0.127, r = 0.97), D (y = 0.247x - 0.354, r = 0.99), and AR (y = 0.087x - 0.083, r = 0.96) wav es. Consistent with numerical modeling, the convective term strongly correl ates with but significantly underestimates actual gradient because of large inertial forces.