Pulmonary vascular resistance in complete atrioventricular septal defect. A comparison between children with and without Down's syndrome.

Invasive data obtained in children with complete atrioventricular septal defect over the last three years are presented to determine the age at which pulmonary vascular obstructive disease develops. Comparisons were made between children with (n = 21) and without Down's syndrome (n = 12). The investigation was restricted to patients less than one year of age at initial catheterization. Patients with complicated associated heart defects were excluded. Patients with Down's syndrome had a higher ratio of pulmonary to systemic vascular resistance than children without Down's syndrome in the basal situation. This difference almost disappeared after 100% oxygen had been given to patients with elevated pulmonary vascular resistance, indicating that hypoxia and/or hypoventilation is of importance, especially in children with Down's syndrome. Fixed elevated pulmonary vascular resistance was found in 11% of Down patients under one year, with the youngest patient being 5.5 months old. One child without Down's syndrome may have had fixed elevated pulmonary vascular resistance. It is concluded that all children with complete atrioventricular septal defect should be evaluated and operated on at a very young age.