Oxygen consumption was measured in infants, children, and adolescents during diagnostic heart catheterizations. A total of 825 measurements of oxygen consumption (VO2) was performed in 504 subjects using a semiopen hood system and a paramagnetic oxygen analyzer. In 256 subjects under 3 years of age, body dimensions and heart rate were found to be significant factors for oxygen consumption. The regression equation for both sexes was: VO2/BSA (ml/min.m2) = 3.42.height (cm) - 7.83.weight (kg) + 0.38.HR - 54.1 (r2 = 0.39, SD = 38.7), where BSA is body surface area and HR is heart rate. VO2/BSA was significantly lower in infants less than 3 months of age (133 +/- 33 ml/min.m2) compared with infants of 3-12 months (171 +/- 37 ml/ min.m2; p < 0.01). In 272 children aged 3 years and older and adolescents, gender was a significant factor in oxygen consumption together with BSA and HR. The regression line equation for males was VO2/BSA (ml/ min.m2) = 0.79.HR - 7.4.BSA(m2) + 108.1 (r2 = 0.45, SD = 34.2). The regression line equation for females is VO2/BSA (ml/min.m2) = 0.77.HR - 5.2.BSA(m2) + 106.8 (r2 = 0.43, SD = 34.4). Hematocrit, systemic oxygen saturation, and blood pressure were not significant factors. The predictive value of nomograms for oxygen consumption is limited because of the large interindividual variations not explained by differences in gender, body size, or simple hemodynamic variables. Preferably, oxygen consumption is measured; but if nomograms for oxygen consumption are used for hemodynamic assessment, the wide confidence intervals should be considered.

Left ventricular systolic time intervals (STI) were recorded by non-invasive technique from the axillary artery in fifteen normal newborns from 10-15 min to 70-74 hours after birth. The observed changes in the different STI could almost entirely be related to changes in the isovolumic contraction time (ICT). At the early postnatal recording ICT was only 21.0 msec suggesting an enhanced left ventricular performance compared to prenatal observations. During the following hours ICT increased to 31.6 msec which in some infants may imply a reduced left ventricular performance. This is suggested to coincide with ductal closure.

No abstract

Abstr-cict. Twenty-two children, who were operated on for ventricular septal defects (VSD) at 3-1 1 years of age, were studied 2-1 1 years postoperatively with respect to signs of residual shunt, cardiomegaly, physical capacity and pulmonary resistance at various rates of perfusion. There was evidence of residual shunt in one of the patients at follow-up. This was also the only patient who had persisting cardiomegaly in the group. Exercise tests were as a rule within normal limits. Total pulmonary resistance (TPR) decreased in all instances and was abnormally elevated in 6 patients at the follow-up, as compared t o 12 at the pre-operative study. Total pulmonary resistance index (TRP') was abnormally elevated in 8 patients, as compared to 10 at the pre-operative study. Whereas TPR decreased from an average pre-operative level of 7.9 to 4.2. TPR' average remained virtually unchanged. The two most hyper-resistive patients were found to have identically high resistance indices at the follow-up investigation, indicating little effect on the obstructive vascular lesion. During provoked increase of pulmonary blood flow TPR fell further in nearly all patients. The pressurelflow characteristics of the pulmonary circulation in patients with normal resting vascular resistance (PVR) followed closely the regression line of a normal material. Conversely the 5 patients with elevation of PVR at rest demonstrated a uniformly steep pressurelflow relationship, indicating a rigid vascular basin in these patients. It is suggested that some of the discrepancies that exist in relation to the effect of surgical closure of VSD may be related to the fact that for the most part a growing population is under study. The "natural" history of pulmonary haemodynamics in the growing individual constitutes a potential error for the long-term evaluation of the effect of VSD closure on pulmonary vascular resistance. It is recommended that resistance figures based on body-sizerelated flow indices are used and that particularly when the postoperative investigation reveals a moderately hyperresistive patient or a "borderline" case, the resistive characteristics of the pulmonary circulation be studied at various flow rates. Our results support the opinion that the VSD patient should be operated on before a markedly obstructive vascular lesion has developed since there is little evidence to suggest a reversibility of the disease. I 1-802916 Scand J Thor Cardiovusc SurR 14 Scand Cardiovasc J Downloaded from informahealthcare.com by QUT Queensland University of Tech on 11/01/14For personal use only.