The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability |
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Authors: | G Cloutier L Allard Z Guo L -G Durand |
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Institution: | 1. Laboratoire de Génie Biomédical, Institut de Recherches Cliniques de Montréal, 110 avenue des Pins Ouest, H2W 1R7, Montréal, Québec, Canada 2. Institut de Génie Biomédical, Ecole Polytechnique, Université de Montréal, Québec, Canada 4. Laboratoire de Recherches Non-invasives en Cardiologie Vasculaire, H?pital H?tel-Dieu de Montréal, Québec, Canada 5. Department of Electrical Engineering, McGill University, Montréal, Québec, Canada
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Abstract: | The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability was investigated in 30
patients. Beat-to-beat variations in the amplitude of Doppler spectrograms were also analysed. The quantification of amplitude
variability was based on the computation of the area under the absolute value of the derivative function of each spectrum
composing mean spectrograms. Fast Fourier transform using a Hanning window was used to compute Doppler spectra. Results obtained
over systolic and diastolic periods showed that the reduction of amplitude variability followed an exponentially decreasing
curve characterised by the equation f(r)=100e−β(r−1), where r is the number of cardiac cycles, β the exponentially decreasing rate, and 100 the normalised variability for r=1.
In systole, the decreasing rate β was 0·165, whereas in diastole it was 0·225. Reductions of the variability in systole for
a number of cardiac cycles of 5, 10, 15, and 20 were 48, 77, 90 and 96 per cent, respectively. In diastole, reductions of
the variability for the same numbers of cardiac cycles were 59, 87, 96 and 99 per cent, respectively. Based on these results,
it can be concluded that no significant improvement in the reduction of amplitude variability may be obtained by averaging
more than 20 cardiac cycles. |
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Keywords: | Amplitude smoothness Aortic valve Beat-to-beat amplitude variation Digital signal processing Doppler ultrasound spectrum Left ventricular outflow tract Statistical variance |
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