Effect of early and late cord clamping on the systolic time intervals of the newborn infant.

The effect of early and late cord clamping on the left ventricular performance of the newborn infant was assessed by measuring the systolic time intervals from the indirect carotid pulse tracings and simultaneous phonocardiogram and electrocardiogram. The study was performed in 13 normal, full-term infants sequentially at 20-105 min, 6-6 1/2 hrs, and 24-27 hrs of age. The umbilical cords were clamped early in 7 (E.C.) and clamped late in 6 infants (L.C.). The ratio of the pre-ejection period (PEP) to the left ventricular ejection time (LVET) was found to be significantly higher in the L.C. infants (mean +/- S.E., 0.400 +/- 0.18, 0.433 +/- 0.018, 0.410 +/- 0.021) compared with those of the E.C. (0.334 +/- 0.010, 0.347 +/- 0.009, 0.361 +/- 0.007) with p values of less than 0.01, less than 0.005 and less than 0.05, respectively in the three examination periods. The higher PEP/LVET ratios in the L.C. infants were mainly attributable to a prolongation of the PEP. It is suggested that late cord clamping, by allowing a sizable placental transfusion, appeared to affect adversely the left ventricular performance of the neonate. Furthermore, it is suggested that in evaluating systolic time intervals of the neonate during the first days of life, the volumic state or status of placental transfusion should be taken into consideration as a determinant.