Simplified Bernoulli's method significantly underestimates pulmonary transvalvular pressure drop

Abstract

Purpose To determine whether neglecting the flow unsteadiness in simplified Bernoulli's equation significantly affects the pulmonary transvalvular pressure drop estimation. Materials and Methods 3.0T magnetic resonance imaging (MRI) 4D velocity mapping was performed on four healthy volunteers, seven patients with repaired tetralogy of Fallot, and thirteen patients with transposition of the great arteries repaired by arterial switch. Pulmonary transvalvular pressure drop was estimated based on two methods: General Bernoulli's Equation (GBE), ie, the most complete form; and Simplified Bernoulli's Equation (SBE), known as 4V2. More than 2300 individual pressure drop measurements were used to compare the simplified and the general Bernoulli's methods. A linear mixed‐effects model was employed for statistical analyses, fully accounting for clustering of observations among the methods and systolic phases. Results The simplified Bernoulli's method systematically underestimated the pressure drop compared to general Bernoulli's method during the entire systolic phase (P < 0.05), including the peak systole, where on average ΔpSBE/ΔpGBE=78%. Conclusion The simplified Bernoulli method underestimated the pressure drop during all systolic phases in all the studied subjects. Therefore, it is necessary to take into account the flow unsteadiness for more accurate estimation of the pressure drop. J. Magn. Reson. Imaging 2016;43:1313–1319.

Validation of pressure drop assessment using 4D flow MRI‐based turbulence production in various shapes of aortic stenoses

“…Therefore, the true pressure drop and the predicted pressure drop, based on the simplified Bernoulli method are not directly interchangeable. The discrepancy between the simplified Bernoulli estimation and the true pressure drop has frequently been reported . Therefore, it functions as a relative metric for clinical cut‐off rather than a true pressure prediction .…”

“…Doppler echocardiography and PC‐MRI have been widely used to measure peak blood velocity at the aortic valve stenosis and to estimate the corresponding pressure drop, because of their non‐invasive nature and clinical accessibility . Time‐resolved, three‐directional, and 3D phase‐contrast MRI (that is commonly abbreviated as 4D PC‐MRI or 4D flow MRI) has recently been developed, and clinical applications of 4D flow MRI for the assessment of pressure drop have been demonstrated based on the method’s non‐invasive and multi‐dimensional velocity assessment . Despite that the Bernoulli method provides various advantages for pressure drop estimation, discrepancies between Bernoulli‐based prediction and invasive pressure measurement are frequently observed because of its inherent underestimation of pressure recovery in the post‐stenotic region .…”

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“…Hence, echocardiographic particle image velocimetry relies on the spatial resolution of the echocardiography images, and is more error-prone than true vector velocity signal when operating within the penetration depth limitations of the vector flow imaging technology. Furthermore, the spatial resolution of standard echocardiography has not been sufficient for echocardiographic particle image velocimetry to be clinically useful (20,23).…”

4D Flow MRI quantification of blood flow patterns, turbulence and pressure drop in normal and stenotic prosthetic heart valves

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