There are certain important physiological changes seen in valvular
regurgitation that are measured during echo to make a full assessment.
Most of these principles are applicable to the mitral valve and are useful
in the assessment of mitral regurgitation.
Firstly, the regurgitant jet flows through the valve at a velocity that is
directly related to the pressure difference (∆P) across the valve. The
velocity (v) is calculated using continuous wave doppler, and is
calculated using the formula
∆P = 4(v2)
When a jet of blood passes through a valvular orifice, the narrowest part
of jet visible on colour doppler is the vena contracta. The vena contracta
is therefore reflective of the functional size of the valvular orifice.
Altering the aliasing velocity helps calculation of PISA. The flow rate of
blood across a regurgitant valve is directly related to the aliasing velocity.
In chronic valvular regurgitation, the volume overload causes an increase
in LV size. The thickness of the walls is retained and thus there is an
increase in its mass.
Of course, the total LV stroke volume is the sum of the flow across
the aortic valve and the regurgitant flow across across the mitral valve.
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