Quantification of mitral regurgitation by integrated Doppler backscatter power

Cardiac Investigation Unit, St. Vincent's Hospital, Fitzroy, Victoria, Australia.

OBJECTIVES. We attempted to determine whether continuous wave Doppler backscatter power could be used to quantify mitral regurgitation. BACKGROUND. The power of a Doppler backscatter signal is proportional to the number of scatterers insonated and, hence, to the moving volume of blood. The relative power of the continuous wave Doppler signals from mitral inflow and aortic outflow is therefore proportional to the relative volumes of blood in motion. METHODS. Computer postprocessing was used to derive the relative power of the Doppler backscatter signal from the intensity of the pixels within the spectral display of anterograde aortic and mitral flow. The power ratio was used to calculate the regurgitant fraction in 20 patients (mean age 61.4 years) with mitral regurgitation. This Doppler regurgitant fraction was compared with that derived from angiographic left ventricular volume and thermodilution cardiac output. In addition, 12 normal control subjects were studied by the Doppler method. RESULTS. Mean (+/- SD) catheterization regurgitant fraction was 0.50 +/- 0.26, and mean Doppler regurgitant fraction was 0.47 +/- 0.25 (r = 0.89). The limits of agreement between the two methods by Bland-Altman analysis were -0.21 + 0.27. In normal control subjects with an expected regurgitant fraction of close to zero, mean Doppler regurgitant fraction was 0.03 +/- 0.05. CONCLUSIONS. Doppler backscatter power from mitral and aortic inflow provides a new and accurate method for quantifying mitral regurgitation.

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