A Doppler Catheter Technique Using Fast Fourier Spectrum Analysis for the Assessment of Coronary Flow Dynamics
The recent development of a catheter-tipped Doppler probe has enabled the measurements of coronary flow velocity in humans. However, the conventional Doppler catheter system with zero-cross signal processing (ZC) contains some limitations in accuracy and reproducibility. Thus, the coronary Doppler catheter was used together with a fast Fourier transform signal processor (FFT), and the resultant system was validated in animal experiments. Further more, this Doppler system was applied to the beat-to-beat assessment of coronary flow dynamics in various clinical settings.
The FFT Doppler catheter system was validated by monitoring the coronary flow in the canine coronary artery with an electromagnetic flowmeter (EMF). The phasic flow velocity obtained with the FFT system remained constant regardless of the sample volume position (range, 2–10mm from the probe). The flow velocities obtained by the FFT system agreed well with those estimated by EMF, while the velocities obtained by ZC significantly underestimated those by EMF even at the optimal sample volume position.
Phasic coronary flow velocity patterns changed in various clinical settings. For example, in patients with aortic regurgitation, the systolic peak often exceeded the diastolic peak flow, differing from the normal pattern of predominance in diastole over systole. In patients with dilated cardiomyopathy, the time from the initiation of the diastolic flow to the diastolic peak flow was longer than that in normal subjects, suggesting an attenuation in early diastolic flow increase. Hence, the catheter-tipped Doppler probe together with FFT has potential in evaluating various coronary flow dynamics in catheterization laboratories.
KeywordsFast Fourier Transform Coronary Flow Aortic Regurgitation Coronary Flow Reserve Electromagnetic Flowmeter
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