Effective Regurgitant Orifice by Continuity Equation
Tricuspid Regurgitation
· Dr. Kenneth Gross ·
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Calcs>Tricuspid Regurgitation>ERO by CE>1
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TV Diameter
cm
TV VTI cm
Regurgitant Jet VTI cm
LVOT Diameter cm
LVOT VTI cm
 
TV CSA cm2
TV SV mls
LVOT CSA cm2
LVOT SV mls
RV mls
ERO cm2

 

Formulas:

LVOT-CSA = 0.785 * LVOT-Diam2

TV-CSA = 0.785 * TV-Diam2

LVOT-SV = LVOT-CSA * LVOT-VTI

TV-SV = TV-CSA * TV-VTI

RV = TV-SV - LVOT-SV

RF = RV / TV-SV

ERO = RV / RJVTI

 
How to get a ERO in Tricuspid Regurgitation.
 
Step 1: Measure the Diameter of the LVOT. The diameter can be of the LVOT should be obtained from the midesophageal AVLAX view, in mid systole, and under the zoom mode.  The view of the LVOT should not be an obtuse angle view.  The aortic valve leaflets (NCC and RCC) should be clearly seen.  The zoom mode will decrease the error present in the calculation.  Since the LVOT diameter changes throughout systole, the mid systole measurement should be obtained. 
 
Step 2: Obtain a VTI of the LVOT.    The VIT of the LVOT is obtained from a PWD of the LVOT.   The PWD of the LVOT should be obtained at the same location as the LVOT diameter measurement.  The PWD beam should not be off more than 15° from parallel to the LVOT flow.  After tracing the flow on the echocardiographic machine, a VTI of the PWD tracing will be calculated.  A continuous wave doppler (CWD) of the LVOT could be obtained, but, since the CWD introduces ambiguity into the equation and since flows in the LVOT rarely exceed the aliasing velocity of the pulse wave doppler, PWD is the best measurement mode.  However, in aortic regurgitation, there is excessive flow, so aliasing may occur.  Therefore, CWD may be required to be able to trace the whole flow profile.
 
Step 3: Obtain a Tricuspid Valve Diameter. The area of the tricuspid valve can be calculated from this measurement.  This may enter some inaccuracy into the equation since the tricuspid valve is not a circle (it is oval). 
 
Step 4:  Obtain a Tricuspid Valve VTI.  Using the PWD mode, trace the envelope of the entire (E wave and A wave) flow profile of the tricuspid valve.  The diastolic flow profile is the TV VTI whereas the systolic flow profile is the regurgitant jet VTI (RJVTI).
  

 
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