Effective orifice area assessment in BI-leaflet mechanical valves by MRI,
Résumé
Effective orifice area (EOA) and mean pressure gradient
are routine echocardiographic measurements of valvular
prosthesis function in both the mitral and aortic position.
EOA computation is based on the continuity equation
and is used to describe the “effective” orifice formed by
the flow traversing a geometrical orifice. In the case of
bi-leaflet biomechanical valvular prosthesis (BMHV),
the orifice of the valve is divided into 3 zones. BMHV
performance assessment by MRI have been described in
the in-vitro setting in [1] using the maximum pressure
gradient. Additionally, a method using jet layer has been
used to detect EOA dynamically [2]. 4D-PC flow
sequences enable measurement of three velocity
components by MRI with a temporal resolution
averaging (~ 30 msec). In patients with a BMHV,
despite the metallic blurring due to the valve structure,
MRI examination enhances both anatomical and
hemodynamic diagnosis. Aim of this work is to assess
the capacity of MRI to measure BMHV EOA by 4D-PCflow
MRI, using simple computational fluid dynamic
(CFD) simulation for validation.