Pulsed‐Doppler Assessment of Ascending Aortic Flow Velocity in Newborns and Infants: Clinical Applications

Abstract

Continued advances in Doppler ultrasound methods have provided a noninvasive technique for analysis of blood flow velocity within the chambers of the heart, across the cardiac valves, and in a variety of vessels.'-4 Recently, these techniques have been applied successfully to insonation of the ascending aortic flow stream in newborns and infants, allowing quantification of ascending aortic blood velocity and estimation of left ventricular cardiac These noninvasive methods provide clinically useful information about overall systemic oxygen delivery, hemodynamics, and myocardial function in a variety of settings where application of invasive techniques would be problematic.This article will review our experience with pulsed-Doppler derivation of ascending aortic blood velocity and estimation of left ventricular cardiac output in newborns and infants. Clinical applications and limitations of this method are also addressed. Instrumentation and MethodsAt our institution, ascending aortic blood velocity signals are obtained in newborns and infants using 5-or 3.5-MHz, ranged-gated, pulsed-Doppler velocimeters* and an appropriate "hammer head" suprasternal transducer or duplex-Doppler imaging probe. * Normal Q A o for neonates = 230 k 50. CV = cardioversion; bpm = beats per minute; Q A o = cardiac output.

Reproducibility of measurements of cardiac output in newborn infants by Doppler ultrasound.

“…7 We conclude that Doppler ultrasound is a useful technique for serially measuring cardiac output in an individual infant. The most reproducible results are obtained using diameters measured by M mode trailing edge to leading edge echocardiography, mean blood and flow velocities measured by continuous wave Doppler at the suprasternal site; the measurements should be made by the same observer on each occasion.…”

“…Alverson et al, 7. Mellander et al,8 and Walther et al9 We are surprised that the results obtained by Walther et al are similar to ours, as well as to those of Mellander et al and Alverson et al, because they calculated aortic diameter using the leading edge to leading edge method; Mellander et al and Alverson et al used the trailing edge method, and we found a 2 mm difference in the leading edge compared with the trailing edge method for measuring diameter.…”

“…Alverson 7 Mellander et al, who used both the cross sectional image for internal aortic diameter and M mode trailing edge to leading edge method, found the M mode more satisfactory.8 As the area is derived from the square of the radius, any error in the measurement of the diameter will be magnified.…”

Cerebral blood flow and left ventricular output in spontaneously breathing, newborn preterm infants treated with caffeine or aminophylline

“…LVO is calculated as follows: D2 T X -x V x 6 0 ml/kg/min BW where BW = birth weight in kg. This method has been found to correlate well with cardiac output measured with thermodilution in infants (6,7).…”

The repeatability of echocardiographic determination of right ventricular output in the newborn

“…Assessment of left ventricular output with echocardiography is now an established research tool in the neonatal setting, having undergone studies of validation and repeatability. [1][2][3][4][5][6] At all ages, the largest source of errors in repeatability is the measurement of diameters of vessels. [8][9][10][11] Since cardiac output is derived by multiplying stroke distance and heart rate by cross-sectional area (p r 2 ), any error in diameter, and hence radius, is squared.…”