Asymmetry of cerebral blood flow velocity in low birth weight infants

Background: In premature infants, intraventricular hemorrhage occurs more commonly in the left than the right hemisphere. We have demonstrated previously that cerebral blood flow velocity is lower in the left than the right middle cerebral artery in the first few hours after birth. This may be due to the open ductus arteriosus. Objective: To test the hypothesis that blood flow velocity is lower in the left than the right middle cerebral artery only when the ductus arteriosus is open. Study Design: Infants born at 25-33 weeks' gestation were enrolled. Middle cerebral artery blood flow velocities and coefficients of variation were measured on the left, followed by the right, on days 1 and 7 of life. Echocardiography identified 67 infants (25-33 weeks, 517-2,371 g) whose ductus arteriosus was open on day 1 and closed on day 7. Results: Systolic (26.4 ± 7.4 vs. 29.6 ± 7.2 cm/s), mean (12.4 ± 4.0 vs. 15.6 ± 4.6 cm/s) and end-diastolic (5.3 ± 2.2 vs. 6.8 ± 2.9 cm/s) blood flow velocities were lower (p < 0.01) and the corresponding coefficients of variation were higher (p < 0.01) on the left on day 1. Neither the absolute Doppler blood flow velocities nor the coefficients of variation differed between the left and right sides on day 7. Conclusions: Blood flow velocity is lower and more variable in the left compared to the right middle cerebral artery on day 1 of life in premature infants. These differences are not found on day 7. We speculate that this difference is due to the associated ductus arteriosus patency.