Doppler and electromagnetic comparisons of instantaneous aortic flow characteristics in primates

Assessment of the pulsatile mechanical behavior of the coupled left ventricle and the peripheral arterial circulation requires accurate estimation of instantaneous aortic flow. Before the availability of Doppler technologies, this could only be achieved by invasive techniques. The purpose of this study was to assess the accuracy of Doppler-based measurement of instantaneous aortic blood flow and waveform morphology throughout ventricular ejection when compared with an established invasive method. Accordingly, data from electromagnetic flow and continuous-wave aortic Doppler recordings were simultaneously acquired and compared in five monkeys over a wide range of flows generated by intravenous infusions of the beta-adrenoceptor agonist dobutamine and the alpha-receptor agonist methoxamine. Instantaneous aortic pressure was measured using a high-fidelity micromanometer-tipped catheter placed in the ascending aorta. Excellent correlations were noted for stroke volume, cardiac output, left ventricular ejection time, maximal flow velocity, and maximal rate of change of flow velocity (dQ/dtmax). When compared with electromagnetic flows, continuous-wave aortic Doppler had significantly lower times to maximal flow velocity and dQ/dtmax. Frequency domain analysis indicated that both the magnitude and phase were within +/- 6% up to the third harmonic. Instantaneous comparison disclosed that during early systole (up to 10% of ejection) Doppler was higher than electromagnetic flow rate by 11 +/- 19% (p less than 0.05). At 20-30% of systolic ejection, electromagnetic flow rates were slightly higher than Doppler (5 +/- 4% at 20% of ejection, p less than 0.001 and 2 +/- 3% at 30% of ejection, p less than 0.05). From 40% of ejection to the end of systole, flow rates using both techniques were virtually identical.(ABSTRACT TRUNCATED AT 250 WORDS)