Regurgitant Fraction by Continuity Equation in Aortic Regurgitation

Regurgitant Fraction by Continuity Equation
Formula:LVOT SV = (0.785 * LVOT Diameter²) * LVOT VTIMV SV = (0.785 * MV Diameter²) * MV VTIRV = LVOT SV - MV SVRF = (RV / LVOT SV) * 100

How to get a Regurgitant Fraction by Continuity Equation.

  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.
  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.
  3. Obtain a Mitral Valve Diameter. The area of the mitral valve can be calculated from this measurement. This enter some inaccuracy into the equation since the mitral valve is not a circle (it is oval). Therefore, the pulmonary valve could be used instead. This measurement is to be used to generate a value that represents normal forward flow in the cardiac cycle.
  4. Obtain a Mitral Valve VTI. Using the PWD mode, trace the envelope of the entire (E wave and A wave) flow profile of the mitral valve.