Resistance index (RI) is used to evaluate cerebral blood flow. We previously reported that changes in systemic flow also influenced the RI. We recently observed two infants with congenital heart disease who evidenced not only an abnormal RI, but also changes in patterns of cerebral blood flow. Case 1 was a 5-month-old boy with Down's syndrome and endocardial cushion defect. He developed heart failure with impending shock, accmpanied by bacterial diarrhea. The Doppler frequency spectrum at the anterior cerebral artery three days after his condition worsened showed a diastolic peak, and on the next day, revealed two diastolic peaks. Abnormal flow was seen at the ascending aorta, the left common carotid artery and the descending aorta. The administration of catecholamines led to improvement, and the diastolic peak at the anterior cerebral artery and the abnormal flow at the other vessels disappeared. Case 2 was an 8-day-old boy with hypoplastic left ventricle syndrom. His systolic flow came through the ductus arteriosus, and ascended via the descending aorta, circulating to the head and extremities. The flow parrern at the basilar artery was irregular with the peak in the end-systolic to early-diastolic period.
