Oxygen consumption in infants and children during heart catheterization.

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 in preterm infants with patent ductus arteriosus.

Left ventricular systolic time intervals were recorded by a non-invasive technique, from the axillary artery, in 13 preterm infants with patent ductus arteriosus. At the onset of clinical symptoms, consistent with a large left-to right ductal shunt, the preejection intervals were shorter than in a control group of nine preterm infants without a patent ductus. The most pronounced difference was found in the shortening of the isovolumic contraction time, 10.7 msec in the ductus group compared with 22.4 msec in the control group. Ductal closure normalized the isovolumic contraction time to 22.1 msec. The very short preejection intervals, associated with a large ductal shunt, are suggested to reflect a combination of reduced aortic diastolic pressure and increased left ventricular filling pressure. In spite of increased volume load to the left ventricle there were no detectable changes in the systolic time intervals indicating impaired left ventricular function. The left ventricle seems to be competent to handle increased volume load in the presence of reduced afterload in preterm infants with symptomatic left-to right ductal shunts.

Assessment of left ventricular adaptation to extrauterine circulation.

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.

Detachment of the septal tricuspid leaflet during transatrial closure of isolated ventricular septal defect.

In 27 (18%) of the 151 patients who underwent transatrial closure of isolated ventricular septal defect (VSD) between 1966 and 1979, the tricuspid valve was partially detached in order to achieve better exposure. All 27 patients had defects of the membranous or paramembranous type situated behind the tricuspid septal cases, tight chordae tendineae crossed over the defect and inserted in the edge of the VSD. A 15 to 20 mm incision in the septal leaflet was usually needed to expose the defect sufficiently. There were two operative deaths among the 27 patients, both unrelated to the tricuspid incision. The remaining patients had uncomplicated postoperative courses. There were no long-term complications or instances of significant tricuspid valve incompetence, major residual shunt, or heart block at follow-up. Three patients, operated upon at the ages of 3, 3, and 6 years, respectively, had residual pulmonary hypertension. In one patient, who died 4 years postoperatively in a traffic accident, the tricuspid valve was intact and the previous incision could hardly be seen. It is concluded that detachment of the septal tricuspid leaflet is a safe procedure during transatrial closure of a VSD.

Ventricular dynamics after surgical closure of VSD.

Twenty patients varying in age between 5 and 20 years at the time of surgical closure of VSD were studied 2 to 9 years postoperatively. Ventricular function was studied by echocardiography and measurement of systolic time intervals for the left and right ventricles and the findings were related to clinical and haemodynamic results of operation. The VSD was closed in all instances and the haemodynamic situation was normalized in all but 2 patients who had persisting pulmonary vascular disease. Right bundle branch block (RBBB) was recorded in 11 instances and in 5 there was an associated left axis deviation (LAD), suggesting left anterior hemiblock. LAD occurred as an isolated anomaly in another 2 patients. The heart size was within normal limits in all the patients. Abnormal septal motion (ASM) was recorded in 13 of the 20 patients, but other echocardiographic analyses, such as LV end-diastolic dimension, left atrial/aortic root ratio, posterior wall velocity index and maximal endocardial velocity, were all within predicted normal limits. There was an almost uniform prolongation of both left and right pre-ejection periods. left and right ejection period as a rule remained normal and gave an increased PEP/ET ratio, indicating the presence of postoperative ventricular dysfunction also in instances with complete normalization of the haemodynamic situation. Suggested background mechanisms for these findings are the frequent occurrence of conduction defects postoperatively, the likelihood of altered ventricular compliance and possibly also as a cause of ASM postoperative presence of an opened pericardial sac.

I. Validity of dichnomatic earpiece densitometry for quantitative studies in children with shunt-free cardiovascular malformations.

Cardiac output was assessed in 16 children without evidence of cardiovascular shunts from simultaneously recorded earpiece and cuvette densitometric tracings. The earpiece set-up was calibrated by the end-tail method. Both instruments gave linear response to dye concentrations used. There was a close correlation between cardiac output figures recorded by the two methods (r equal to 0.95) and no systematic difference occurred. It is concluded that in infants and children earpiece densitometry constitutes a rapid and accurate method for quantitative circulatory studies.

V. Exercise studies in children with congenital heart disease. An earpiece densitometric investigation.

Twenty-three patients have been studied by exercise testing during right heart catheterization. Cardiac output was measured by the earpiece densitometric technique before, during and after the exercise period. It is concluded that the earpiece densitometric technique in conjunction with exercise testing offers an attractive alternative for the study of pressure and flow characteristics in children with congenital heart disease.

II. Cardiac output studies in infants and children undergoing right heart catheterization.

Cardiac output figures from 97 patients were computed by earpiece densitometry and correlated to various dimensional parameters. Stroke volume was better correlated to body dimensions than cardiac output indicating that patients undergoing right heart catheterization were not in basal state.

III. Evaluation of the forward triangle area in dye curves from infants and children studied by earpiece densitometry.

Onehundred and six dye curves recorded by earpiece densitometry in shunt-free children were analysed with respect to the spatial relationships between the forward triangle and the area under the total primary dye curve. It is suggested that the relationship between these two areas, the forward triangle factor, should be 0.32 for studies in children with the use of dichromatic earpiece densitometry.

IV. Evaluation of dichromatic earpiece densitometry in children with left-to-right shunts.

Earpiece densitometry was performed in 60 infants and children with left-to-right cardiovascular shunts. The method was found to possess a high diagnostic sensitivity with respect to identification of the left-to-right shunt. Earpiece densitometry was in this respect clearly superior to conventional method using oxygen saturation figures. Quantitation of pulmonary blood flow by both densitiometric and oxygen content technique in a small number of patients indicates that the dye dilution technique gives values somewhat in excess of the Fick method. It is concluded that quantitation of the magnitude of the left-to-right shunt and pulmonary blood flow is disturbed by the fact that indicator material is recirculated before the ascending limb of the primary curve is fully inscribed.