Cardiac function and morphology studied by two-dimensional Doppler echocardiography in unsedated newborn pigs

The newborn pig is currently the most used species in animal neonatal resea rch. Valid noninvasive monitoring is important in particular for long-term survival of unsedated animals. In the unsedated newborn pig (n = 35, median age 24 h, range 7-48 h) we standardized two-dimensional Doppler echocardio graphy and determined the normal ranges for cardiac function. Probe positio ning had to be adjusted to the V-shaped thorax and the mid-line position of the heart. Six out of the sixteen animals < 20 h had a patent ductus arter iosus compared with one of the twenty animals > 20 h old. One atrial septal defect (5 mm) and one small ventricular septal defect were diagnosed. The average heart size was 0.7-0.9 % of body weight which is similar to human i nfants of the same size. The mean aortic diameter was 6.0 +/- 0.5 mm (mean +/- S.D.) and cardiac output was 0.38 +/- 0.08 1 min(-1) both correlate wit h body weight (r = 0.80 and 0.73, respectively). Tricuspid regurgitation ve locity was 3.0 +/- 0.4 m s(-1) (mean +/- S.D.), giving an estimated pressur e gradient across the tricuspid valve of 37 +/- 9.7 mmHg. The aortic diamet er and the heart weight per kg body weight are comparable to those reported for preterm neonates. The cardiac output and velocities across the four va lves are more comparable with term neonates.