EFFECTS OF VELOCITY DISTRIBUTION, DIAMETER MEASUREMENT AND VELOCITY TRACING ON THE ACCURACY OF CARDIAC-OUTPUT MEASUREMENT BY PULSED DOPPLER-ECHOCARDIOGRAPHY IN THE AORTIC ANNULUS OF PIGS

The accuracy of cardiac output measurement by pulsed Doppler echocardi ography can be affected by several factors, such as the velocity distr ibution, the measurement of diameter and the method of tracing the pul sed Doppler flow spectrum, This experimental study was designed to fin d the most accurate way of measuring cardiac output in consideration o f all these factors, In 10 open-chest normal piglets (24 +/- 1 kg), th e velocity distribution in the aortic annulus was evaluated using Dopp ler colour how mapping, Cardiac output was measured by pulsed Doppler echocardiography in the aortic annulus by a number of different ways a nd compared to the simultaneous result of the thermodilution method, A ll measurements were made at baseline, after intravenous injection of esmolol and during infusion of dobutamine, Results: (1) the velocity d istribution in the aortic annulus in the piglets was just slightly ske wed during all three haemodynamic situations; (2) The in vivo measurem ents of the diameter of the aortic annulus varied throughout the eject ion period, but the average of the three largest diameter measurements was almost identical with the diameter measured in vitro (18.5 +/- 0. 3 mm vs, 18.6 +/- 0.2 mm; p = NS); (3) Tracing the maximal velocity of the pulsed Doppler flow spectrum produced a cardiac output that was 1 8%-21% higher than that measured by the thermodilution method, while t racing the brightest part (modal velocity) of the pulsed Doppler flow spectrum yielded a cardiac output very close to the thermodilution mea surement, Conclusion: The velocity distribution in the aortic annulus in the piglet has little effect on cardiac output measurement by pulse d Doppler, Using the maximal measurable diameter of the aortic annulus and tracing the brightest part of the pulsed Doppler how spectrum yie lded the cardiac output closest to that measured by the thermodilution method. (C) 1997 World Federation for Ultrasound in Medicine & Biolog y.