DOPPLER-ECHOCARDIOGRAPHIC STUDY OF THE PULMONARY-ARTERY AND ITS BRANCHES IN 114 NORMAL NEONATES

It has been shown that there are pressure gradients between the main p ulmonary artery (MPA) and its two branches in infants undergoing cathe terization. This study investigated the blood flow velocities and pres sure gradients in the right and left pulmonary arteries (RPA and LPA, respectively) in normal neonates. The MPA and its two branches were ex amined echocardigraphically in 114 term consecutive healthy neonates a ged 1-6 days. The pressure gradients between the MPA and RPA or LPA we re calculated. Thirty neonates with pressure gradients above 2.5 mmHg were followed by 3-6 months. The peak velocities in the RPA and LPA (1 .16 +/- 0.19 and 1.01 +/- 0.18 m/s) were significantly higher than tha t in the MPA (0.84 +/- 23 m/s) (both p < 0.001), with that in the RPA slightly higher than in the LPA (p < 0.001). There was an estimated pr essure gradient of 2.5-8.3 mmHg between the MPA and RPA in 43% and of 2.5-6.6 mmHg between the MPA and LPA in 16.7% of all neonates. The gra dients disappeared within 3-6 months in 12 (40%) of the 30 neonates wi th an initial gradient above 2.5 mmHg. The differences in blood flow v elocities or pressure gradients in the RPA or LPA were probably attrib utable to the variations in pulmonary arterial pressure, cardiac outpu t, age, and birth weight and can be considered physiologically charact eristic in neonates.