Clinical applications of echocardiography in infants and children. I. Investigation of infants and children without heart disease

Normal values of M mode echocardiographic measurements of more than 2000 healthy infants and children in central Europe

OBJECTIVE

To obtain normal M mode (one dimensional) echocardiographic values in a substantial sample of normal infants and children.

DESIGN

Data were obtained over three years from a single centre in central Europe.

PATIENTS

2036 healthy infants and children aged one day to 18 years.

METHODS

In line with recommendations for standardising measurements from M mode echocardiograms, and using digital echocardiographic equipment, measurements were obtained of the following: right ventricular anterior wall thickness at end diastole, right ventricular end diastolic dimension, thickness of interventricular septum at end diastole and end systole, thickness of posterior wall of the left ventricle at end diastole and end systole, left ventricular dimension at end diastole and end systole, pulmonary and aortic valve diameter, and left atrial dimension.

RESULTS

Measurements are presented graphically on centile charts with respect to body surface area, and as tables with mean and 2 SD values for newborns in relation to body weight, and for infants and children in relation to body surface area. Best fitting regression equations are given for each measured variable, using the 50th centile values.

CONCLUSION

In comparison with previously published normal values, the presented charts and tables make it possible to judge echocardiographic measurements of a particular patient as normal or abnormal.

Evolution of echocardiography in neonatal diagnosis

In the late 1960's, Edler and Lundström introduced ¿ultrasoundcardiography¿ for the evaluation of congenital heart disease. Initial evaluations using A- and M-mode echocardiography produced non-invasive diagnosis of many defects, including specific complex malformations such as hypoplastic left heart, Ebstein's malformation, endocardial cushion defect and transposition, all with single crystal techniques. Normal values for dimensions related to patient size and indices of function developed at that time remain as components of contemporary examinations. Two-dimensional imaging technology has evolved from 20 channels on Bom's linear array to 128-channel systems currently providing detailed imaging of structures as small as neonatal coronary arteries. The contribution of Doppler techniques for qualitative evaluation of blood flow characteristics has been greatly augmented by both the quantitative Doppler methods for accurate assessment of pressure gradients and pulmonary pressure, and by the development of color Doppler display of intracardiac and intravascular flow. These contributions have come from centers worldwide, with many initial and ongoing contributions from Lund. The evolution of instruments, and of application, now provides neonatal echocardiographic delineation of anatomic detail, function and hemodynamics of sufficient clarity and accuracy to replace the need for invasive study, or alternative technologies, in most cases.

Age and body surface area related normal upper and lower limits of M mode echocardiographic measurements and left ventricular volume and mass from infancy to early adulthood

BACKGROUND

M Mode echocardiograms can be measured by two different conventions. In addition, normal limits of echocardiographic measurements have customarily been stratified according to age or body surface area. There is therefore a need to develop a more easily managed approach to calculating normal limits of measurements for the two conventions, one of which, the Penn convention, has not previously been used for echocardiographic measurements in children.

METHODS

M mode echocardiograms were recorded in 127 healthy subjects aged from 7 months to 19.5 years. Measurements were made from paper recordings according to the recommendations of the American Society of Echocardiographers and those of the Penn convention.

RESULTS

Age and body surface area were found to be highly correlated; but for completeness separate age dependent and body surface area dependent equations for the normal limits of M mode echocardiographic variables were developed.

CONCLUSION

A set of age dependent equations and a set of body surface area dependent equations are presented for easy calculation of upper and lower limits of normal M mode echocardiographic variables in infants and children.

Cardiac function in healthy infants and children: Doppler echocardiographic evaluation

To establish normal values for Doppler-derived parameters of cardiac function, pulsed-wave Doppler recordings from the ascending aorta were obtained in 80 healthy infants and children. Stroke and minute distance, peak velocity, mean acceleration, acceleration and ejection time intervals, and the acceleration/ejection time ratios were measured or calculated from the Doppler recordings. The relations between the Doppler parameters and heart rate, age, and body surface area were analyzed separately for the children below and above 6 months of age. The normal values for the two groups are given as the median and range and as the mean and standard deviations, respectively. For the older age group, strong negative correlations with heart rate were found for stroke distance and ejection time, suggesting that these parameters should be evaluated in relation to heart rate. Intraobserver and interobserver reproducibility were studied in 10 children. Good reproducibility was found for stroke and minute distance, peak velocity, and left ventricular ejection time. For measurements related to acceleration, the reproducibility was less good.

Dimensions of cardiac chambers and great vessels by cross-sectional echocardiography in infants and children

A total of 120 healthy infants, children, and teenagers were examined by cross-sectional echocardiography. Right and left atrial and ventricular dimensions and areas were measured in the parasternal, apical, and subcostal views. Dimensions of the inferior caval vein, the pulmonary artery and the aorta were obtained in the parasternal, suprasternal, and subcostal views. Reproducibility was studied in separate material consisting of 19 children with various forms of congenital heart disease examined consecutively by two different observers. Interobserver reproducibility was expressed as the 95% tolerance limit for the difference between two measurements. Good correlation with body surface area was demonstrated for all measurements, and the regression equations for the normal values of the parameters studied are given. Interobserver reproducibility was fairly good for measurements in the parasternal views, but moderate or low for measurements in the apical and the subcostal four-chamber views. Measurements in cross-sectional echocardiography are clinically useful, especially in the study of the right-sided cardiac structures that are difficult to evaluate with M-mode echocardiography, but the problems of reproducibility have to be taken into account.

Diameters of the orifices of the aorta and pulmonary trunk in normal children--an angiocardiographic study

The diameters of the orifices of the pulmonary trunk and aorta were measured from cineangiocardiographic films in 35 children (mean age 7 years and 6 months, mean height 124.3 cm) without heart disease. Measurements were obtained in the lateral projection in early systole. Calipers and a micrometer were used and the values were expressed to the nearest 0.5 mm. The measured size of the intracardiac catheter was used for calibration. The mean ratio of the squared diameters of the orifices was 1.22:1 (SD 0.17). The diameter of the orifice of the pulmonary trunk/100 cm of body height (14.0 +/- 2.0 mm) was greater than that of the aortic (12.7 +/- 2.0 mm) (P less than 0.01). Significant linear correlation was found between the diameter of the orifice of the pulmonary trunk and body height (r = 0.71, P less than 0.001), weight (r = 0.67, P less than 0.001), and surface area (r = 0.70, P less than 0.001). Similar correlations were found for measurements of the aortic orifice and body height (r = 0.70, P less than 0.001), weight (r = 0.71, P less than 0.001), and surface area (r = 0.71, P less than 0.001), and between the diameters of the two orifices themselves (r = 0.91, P less than 0.001). Body weight is more affected than body height in various types of congenital heart disease. The relationship of the sizes of the orifices of the pulmonary trunk and aorta to body height may therefore be more applicable than their relation to body weight and surface area.

M-mode echocardiography in normal children and adolescents: some new perspectives

Normal M-mode echocardiography values were determined using computer-assisted measurements of echocardiograms (ECHO) in 202 children and young adults 25 days to 23 years of age: 77 were female, and 125 were male and, reflecting the population served by our Center, 99 were black and 103 were white children. The values for left and right heart wall thicknesses and chamber sizes were graphically displayed as a function of body surface area, and with an illustration of the regression line and 2 standard deviation (SD) range of normal for each parameter. In addition, normal ECHO predicting equations for dimension and function parameters were derived using multiple linear regression analysis with age, height, weight, sex, race, and heart rate as independent variables. A comparison was made between the observed data and the data derived from the normal predicting equations for each of the parameters. Also, values obtained from these equations were compared to data generated from other published normal predicting equations. A description of the digitizer measurements, computer interfacing, and a sample ECHO report form utilizing the predicted normal ranges for each of the parameters is presented. We propose that quantitative M-mode echocardiographic reporting should be easily accessible to all pediatric cardiology laboratories.

Dimensions of the great arteries, semilunar valve roots, and right ventricular outflow tract during growth: normative angiocardiographic data

Systolic and diastolic diameters of the right and left pulmonary arteries (RPAD, LPAD), descending thoracic aorta (DTAD), right ventricular infundibulum (RVID), and pulmonary and aortic valve roots at the proximal, commissural and distal levels were estimated from angiocardiograms in 24 infants, children, and adolescents without heart disease, and correlated with body surface area (BSA), stroke volume (SV), cardiac output (CO), and ventricular volumes. The relationships between cardiovascular diameters and BSA were better expressed by a power function than by the other functions tried. We obtained different exponents for pulmonary and aortic valve annuli and the more distally measured great arteries (RPAD, LPAD, and DTAD), suggesting different growth patterns. The right ventricular infundibular shortening fraction (RVISF) was weakly correlated with BSA (r = -0.328), and the values obtained indicated constancy during normal growth. There was a direct proportional relationship between the pulmonary valve annulus diameter and the cube root of the right ventricular volume (r = 0.952), as well as between SV and cross-sections of the right pulmonary artery (RPAC; r = 0.916), left pulmonary artery (LPAC; r = 0.878) and descending thoracic aorta (r = 0.962). RPAC and LPAC were strongly correlated (r = 0.940), the RPAC being significantly larger than the LPAC.

Effect of age related changes in chamber size, wall thickness, and heart rate on left ventricular function in normal children

We assessed the effects of age related changes in chamber size, wall thickness, and heart rate of left ventricular function in 78 normal children, aged 1 1/2 to 12 1/2 years, using computer analysis of their left ventricular echocardiograms. Left ventricular cavity size and wall thickness increased linearly with age. Left ventricular fractional shortening, percentage of wall thickening, and the ratio of end-diastolic wall thickness to cavity radius (H/R ratio) did not change with age. Peak Vcf correlated with heart rate and the decrease in heart rate with age resulted in the progressive fall in peak Vcf, while peak rate of left ventricular was thickening remained constant. The peak rate of increase in left ventricular cavity dimension in early diastole varied inversely with heart rate, but independently of cavity size, increasing throughout childhood. The peak rate of wall thinning also increased with age, correlating with wall thickness and not heart rate. Thus, age related increases in left ventricular cavity dimension and wall thickness during the rapid growth period of childhood occurred in such a way that left ventricular architecture (H/R ratio) remained unchanged. This may account for the constancy of regional and cavity systolic function. The greater dependence of diastolic cavity function on heart rate may be explained by the disproportionately greater effect of cardiac cycle length on the duration of diastole and systole.

Echocardiographic measurements in normal subjects. Growth-related changes that occur between infancy and early adulthood

Echocardiographic measurements of the left ventricular dimensions and wall thicknesses at end diastole and end systole, aortic root and left atrial dimensions, mitral valve E-F slope, left ventricular ejection fraction, percent fractional shortening of the left ventricular internal dimension, estimated left ventricular mass and percentage systolic thickening of the ventricular septum and left ventricular free wall were obtained in 105 normal subjects ranging from one day to 23 years of age. Each parameter was found to follow a linear regression upon one of three functions of the body surface area. The internal dimensions of left ventricle, the left atrium, and the aortic root, and the mitral valve E-F slope varied in a linear relation to the cube root of the body surface area. Thickness of the ventricular septum and left ventricular free wall varied in a linear relation to the square root of the body surface area. Estimated left ventricular mass varied linearly with the direct measurement of body surface area. Ejection fraction, percent fractional shortening of the left ventricle and percent systolic thickening of the ventricular septum and left ventricular free wall were independent of body surface area despite a marked increase in the size of the left ventricle during normal growth and development.

Evaluation of left ventricular size and function by echocardiography. Results in normal children

Left ventricular (LV) size and function were studied by echocardiography in 145 normal children. The LV end-diastolic diameter (EDD) and its percentage change with systole (%deltaLVD) were measured and mean velocity of circumferential fiber shortening (Vcf) calculated. The LV pre-ejection period (PEP) and ejection time (LVET) were determined from recordings of aortic valve motion. The EDD increased by approximately threefold during childhood and was best correlated with the log of body weight (r = 0.95) and the log of body surface area (r = 0.96). The mean %deltaLVD was 36 +/- 4 (SD), and this index of LV function was independent of age and heart rate. Mean Vef was higher, and the absolute values of PEP and LVET shorter, in younger children with a faster heart rate. The mean ratio of PEP/LVET was 0.31 +/- 0.003, and was relatively independent of age (r = 0.41) and heart rate (r = 0.37). The %deltaLVD and PEP/LVET appear to be particularly useful indices of LV function because they remain constant during the course of childhood.