The ductus arteriosus: a window for assessment of pulmonary artery pressures?

Changes in pulmonary artery pressure during early transitional circulation in healthy full-term newborns

BACKGROUND

Although pulmonary artery systolic pressures (PASPs) are frequently measured in newborn infants using the tricuspid regurgitant jet velocity or ductal Doppler velocity, little is known about the reference range in the general population.

METHODS

This was a retrospective study of 296 neonates less than 14 days of age who were evaluated using echocardiography. Patients included in this study did not have clinical or acquired cardiac disease. PASP was estimated using the ductal Doppler velocity and/or the tricuspid regurgitant jet velocity and the Bernoulli equation.

RESULTS

The majority of the definite right-to-left through the ductus arteriosus was limited to the first 6 h after birth, and the majority of the left-to-right shunt was limited to 10 h after birth. After 10 h, 24 infants with Doppler color-flow imaging revealed a very small and transient jet. The percentage of measurable tricuspid regurgitation was 91% after 24 h. Multivariable regression analysis found that there was a significant correlation between neonatal age and PASP (determined from tricuspid regurgitant jet velocity and Bernoulli equation: r(2)=0.748, P<0.0001; and from ductal Doppler velocity: r(2)=0.179, P<0.001). The upper 95% limit for PASP measured in healthy neonates younger than 14 days was 39.1 mmHg.

CONCLUSIONS

The ductal Doppler velocity is measured more easily for monitoring PASP than tricuspid regurgitant jet velocity in newborns soon after birth; however, in neonates older than 24 h, the tricuspid regurgitant jet velocity is easier for measurement. Age is an independent impact factor of PASP in the neonates. And PASP values gradually decreased to less than 39.1 mmHg by 14 days after birth.

Ductus venosus flow velocity in newborn lambs during increased pulmonary artery pressure

The aim of the present study was to assess with ultrasound the ductus venosus flow velocity in newborn lambs with increasing pulmonary artery pressures and to evaluate whether this is a useful method to detect elevated pulmonary artery pressure. The ductus venosus flow velocity was studied with pulsed-wave Doppler echocardiography in nine newborn lambs < or = 30 h old. The lambs were anesthetized, mechanically ventilated, and instrumented to measure mean airway pressure and pulmonary artery and arterial blood pressures. A vascular occluder was placed around the main pulmonary artery. With mean pressures ranging from 20 to 50 mm Hg in the pulmonary artery, the ductus venosus flow velocity was examined. In seven lambs, the mean portal pressure and central venous pressure were also measured. With a stepwise increase in the pulmonary artery pressure, the minimum ductus venosus flow velocity during atrial systole decreased to a reversed flow, and the duration of this reversed flow component increased. The systolic forward peak flow velocity signal also gradually decreased. No changes were detected in the mean central venous or in the portal pressure with increasing pulmonary artery pressure or changes in ductus venosus flow. The flow velocity in the ductus venosus, which is higher than in other precordial veins, shows a reduction and even reversal of the nadir and an increase of the duration of reversed flow during atrial systole as a response to increased pulmonary artery pressure. Thus, Doppler ultrasound of the ductus venosus flow velocity may be a useful noninvasive diagnostic supplement to detect pulmonary hypertension of the newborn.

Ductus venosus blood velocity in persistent pulmonary hypertension of the newborn

AIMS

To investigate the ductus venosus flow velocity (DVFV) in infants with persistent pulmonary hypertension of the newborn (PPHN); to evaluate the DVFV pattern as a possible diagnostic supplement in neonates with PPHN and other conditions with increased right atrial pressure.

METHODS

DVFV was studied in 16 neonates with PPHN on days 1-4 of postnatal life using Doppler echocardiography. DVFV was compared with that in mechanically ventilated neonates with increased intrathoracic pressure, but without signs of PPHN (n=11); with neonates with congenital heart defects resulting in right atrial pressure (n=6); and with preterm neonates without PPHN (n=46); and healthy term neonates (n=50).

RESULTS

Infants with PPHN and congenital heart defects with increased right atrial pressure were regularly associated with an increased pulsatile pattern and a reversed flow velocity in ductus venosus during atrial contraction. A few short instances of reversed velocity were also noted in normal neonates before the circulation had settled during the first day after birth.

CONCLUSIONS

A reversed velocity in the ductus venosus during atrial contraction at this time signifies that central venous pressure exceeds portal pressure. This negative velocity deflection is easily recognised during Doppler examination and can be recommended for diagnosing increased right atrial pressure and PPHN.

Reliability and accuracy of measurement of transductal gradient by Doppler ultrasound

Simultaneous continuous wave Doppler echocardiography, aortic and pulmonary artery pressure measurements were performed during cardiac catheterization in 46 patients with patent ductus arteriosus. Doppler-derived systolic, mean and diastolic transductal gradients correlated well with those measured by catheterization, respectively (r = 0.972, SEE = 6.8 mmHg; r = 0.965, SEE = 5.4 mmHg; r = 0.939, SEE = 6.2 mmHg), and there were clinically acceptable agreements between the two technical measurements. It is concluded that Doppler echocardiography is a reliable and accurate technique for noninvasive estimation of transductal gradients.