Vena contracta is defined as the narrowest central flow region of a jet
that occurs at, or just downstream to, the orifice of a regurgitant valve.
It is characterized by high velocity, laminar flow.
It is slightly smaller than the anatomic
regurgitant orifice due to boundary effects.
The cross-sectional area of the vena contracta represents a measure of the effective
regurgitant orifice area, which is the narrowest area of actual flow.
The size is independent of flow rate and driving pressure for a fixed orifice.
If the regurgitant orifice is dynamic, the vena contracta may change with hemodynamics,
or during the cardiac cycle.
In contrast to the to the jet in the receiving chamber, the vena contracta
is less sensitive to technical factors such as pulse repetition frequency.
Because of the small values of the width of the vena contracta (usually < 1 cm),
small errors in its measurement may lead to a large percent error and misclassification
of the severity of regurgitation.
It may be necessary to angulate the transducer out of the normal echocardiographic
imaging planes to separate out the area of proximal flow acceleration,
the vena contracta, and the downstream expansion of the jet.
The color flow sector should be as narrow as possible, with the least depth, to maximize
lateral and temporal resolution.
Full text article on assessment of mitral regurgitation
Grayburn PA, Fehske W, Omran H, Brickner ME, Luderitz B.
Multiplane transesophageal echocardiographic assessment of mitral
regurgitation by Doppler color flow mapping of the vena
contracta. American Journal of Cardiology 1994 Nov 1;74(9):912-7
Assessment of the severity of mitral regurgitation (MR) by
Doppler color flow mapping is limited by dependence of jet area on
hemodynamic and technical variables. The width of the MR
jet at its origin may be less dependent on hemodynamic variables, and
thus should more accurately reflect the severity of MR. Doppler
color flow mapping was performed in 80 subjects by
transesophageal echocardiography (TEE) within 48 hours of catheterization.
Width of the MR jet at its vena contracta was measured by both
single plane and multiplane TEE and compared with the angiographic grade
of MR and regurgitant volume. The width of the MR jet correlated
closely with angiographic grade by both methods. A jet width > or =
6 mm identified angiographically severe MR with a sensitivity
and specificity of 100% and 83% by single-plane TEE, and 95%
and 98% by multiplane TEE. The sensitivity and specificity for
detecting a regurgitant volume > or = 80 ml was 93% and 76% for
single-plane TEE, and 86% and 95% for multiplane TEE. Thus, the width of
the MR jet at its vena contracta by Doppler color flow mapping is
an accurate marker of the severity of MR. By virtue of its
ability to obtain orthogonal views specifically oriented to mitral
leaflet coaptation, multiplane TEE is superior to single-plane TEE
in assessing MR jet width.
Fehske W, Omran H, Manz M, Kohler J, Hagendorff A, Luderitz B.
Color-coded Doppler imaging of the vena contracta as a basis for
quantification of pure mitral regurgitation. American Journal of
Cardiology 1994 Feb 1;73(4):268-74
The narrowest central flow region of a jet is defined as the vena
contracta. This term is applied also to the contracted zone of
the Doppler color flow image of a jet at its passage through an
incompetent mitral valve. The clinical applicability of
measuring the size of the vena contracta by transthoracic color-coded
Doppler echocardiography for estimating the severity of mitral
regurgitation (MR) was evaluated. In 78 of 82 patients with
angiographically proved MR, a coherent flow image across the valve was
visualized. The maximal diameter in the apical long-axis view was
considered as a representative value for the size of the vena contracta.
In comparison with the maximal left atrial velocity pixel
area, this parameter revealed higher correlations to the angiographic
degree of MR and to the regurgitant volume (r = 0.94 vs 0.72, and
0.83 vs 0.71, respectively). The highest positive and negative
predictive accuracies for differentiating mild-to-moderate from severe
MR were determined for a diameter of 6.5 mm (88 and 96%,
respectively). Because the vena contracta is directly related to the
severity of MR, it is concluded that it is helpful to use this
parameter instead of the maximal velocity pixel area for semiquantitative
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