SYSTEMIC BLOOD FLOW IN INFANTS AND CHILDREN WITH AND WITHOUT HEART DISEASE

A technique for measuring cardiac output by the Fick method in small infants during cardiac catheterization is described. Data on resting oxygen consumption, arteriovenous oxygen difference and systemic cardiac output is presented for a group of 126 subjects composed mainly of infants and young children with congenital heart disease. It was found that (a) there was no significant difference in mean resting cardiac index for patients with body surface area under 1.0 square meter regardless of the presence of, or the severity of, heart disease, and (b) patients with heart disease who were larger than 1.0 square meter had significantly lower mean cardiac indices and higher arteriovenous oxygen differences than the control patients. An excellent linear correlation of cardiac output to body surface area was found. There was also a close correlation between index and regression lines for cardiac output leading support to the validity of the cardiac index concept for comparing cardiac outputs in various sized patients. The normal increase in cardiac output during exercise is greater for children than for adults. Forty-seven per cent (8 of 17) children with heart disease showed low cardiac output response to exercise.