TY - JOUR

T1 - Impact of finite orifice size on proximal flow convergence

T2 - Implications for Doppler quantification of valvular regurgitation

AU - Rodriguez, Leonardo

AU - Anconina, Joseph

AU - Flachskampf, Frank A.

AU - Weyman, Arthur E.

AU - Levine, Robert A.

AU - Thomas, James D.

N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

PY - 1992

Y1 - 1992

N2 - Analysis of velocity acceleration proximal to a regurgitant valve has been proposed as a method to quantify the regurgitant flow rate (Q(o)). Previous work has assumed inviscid flow through an infinitesimal orifice, predicting hemispheric isovelocity shells, with calculated flow rate given by Q(c)=2πr(N)2V(N), where V(N) is user-selected velocity of interest and r(N) is the distance from that velocity to the orifice. To validate this approach more rigorously and investigate the impact of finite orifice size on the assumption of hemispheric symmetry, numerical and in vitro modeling was used. Finite-difference modeling demonstrated hemispheric shape for contours more than two orifice diameters from the orifice. More proximal than this (where the measured velocity V(N) exceeded 3% of the orifice velocity V(o)), flow was progressively underestimated, with a proportional error ΔQ/Q(o) nearly identical to the ratio of contour velocity to orifice velocity, V(N)/V(o). For the in vitro investigations, flow rates from 4.3 to 150 cm3/sec through 0.3 and 1.0 cm2 circular orifices were imaged with color Doppler with aliasing velocities from 19 to 36 cm/sec. Overall, the calculated flow (assuming hemispheric symmetry) correlated well with the true flow, Q(c)=0.88Q(o)-7.82 (r=0.945, SD=12.2 cm3/sec, p<0.0001, n=48), but progressively underestimated flow when the V(N) approached the orifice velocity V(o). Applying a correction factor predicted by the numerical modeling, ΔQ was improved from -13.81±13.01 cm3/sec (mean±SD) to +1.54±5.67 cm3/sec. These data indicate that flow can be accurately calculated using the hemispheric assumption as Q(c)=2πr(N)2V(N) when V(N)<<V(o). For larger V(N), flow is systematically underestimated, but a more accurate estimate may be obtained by multiplying Q(c) by V(o)/(V(o)- V(N)). These observations lend additional support for the clinical use of the proximal acceleration concept and suggest a simple correction factor to make a more accurate estimation of valvular regurgitation.

AB - Analysis of velocity acceleration proximal to a regurgitant valve has been proposed as a method to quantify the regurgitant flow rate (Q(o)). Previous work has assumed inviscid flow through an infinitesimal orifice, predicting hemispheric isovelocity shells, with calculated flow rate given by Q(c)=2πr(N)2V(N), where V(N) is user-selected velocity of interest and r(N) is the distance from that velocity to the orifice. To validate this approach more rigorously and investigate the impact of finite orifice size on the assumption of hemispheric symmetry, numerical and in vitro modeling was used. Finite-difference modeling demonstrated hemispheric shape for contours more than two orifice diameters from the orifice. More proximal than this (where the measured velocity V(N) exceeded 3% of the orifice velocity V(o)), flow was progressively underestimated, with a proportional error ΔQ/Q(o) nearly identical to the ratio of contour velocity to orifice velocity, V(N)/V(o). For the in vitro investigations, flow rates from 4.3 to 150 cm3/sec through 0.3 and 1.0 cm2 circular orifices were imaged with color Doppler with aliasing velocities from 19 to 36 cm/sec. Overall, the calculated flow (assuming hemispheric symmetry) correlated well with the true flow, Q(c)=0.88Q(o)-7.82 (r=0.945, SD=12.2 cm3/sec, p<0.0001, n=48), but progressively underestimated flow when the V(N) approached the orifice velocity V(o). Applying a correction factor predicted by the numerical modeling, ΔQ was improved from -13.81±13.01 cm3/sec (mean±SD) to +1.54±5.67 cm3/sec. These data indicate that flow can be accurately calculated using the hemispheric assumption as Q(c)=2πr(N)2V(N) when V(N)<<V(o). For larger V(N), flow is systematically underestimated, but a more accurate estimate may be obtained by multiplying Q(c) by V(o)/(V(o)- V(N)). These observations lend additional support for the clinical use of the proximal acceleration concept and suggest a simple correction factor to make a more accurate estimation of valvular regurgitation.

KW - Doppler echocardiography

KW - finite- difference modeling

KW - flow rate calculation

KW - fluid dynamics

KW - in vitro modeling

KW - proximal flow convergence

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UR - http://www.scopus.com/inward/citedby.url?scp=0026537396&partnerID=8YFLogxK

U2 - 10.1161/01.res.70.5.923

DO - 10.1161/01.res.70.5.923

M3 - Article

C2 - 1568302

AN - SCOPUS:0026537396

VL - 70

SP - 923

EP - 930

JO - Circulation Research

JF - Circulation Research

SN - 0009-7330

IS - 5

ER -