The Electrocardiogram of normal children.

Abstract

Summary.The electrocardiographic investigations comprise 118 children.The cases have been statistically analyzed. In this manner mathematical expressions of range of variation have been obtained, in addition to means, and on this basis a more definite limit of normality has been established. The means here reported differ generally only slightly from those of earlier investigations. As regards the different values see above.Fig. 20 is a schematic picture of the normal child electrocardiogram founded on the present cases. It should here be again emphasized that children from 2 to 14 years of age have been subjected to this examination and that infants have not been included. Apart from means range of variation calculated on ± 2 σ and ± 3 σ will be found in Fig. 20.Different amplitudes and intervals in the child electrocardiogram have in common their palpably great range of variation. In these circumstances it should be obvious that means do not provide sufficient data in differentiating between normal and pathological. Conduction time may be quoted as an instance. The mean is here 0.15 second but values can be regarded as undoubtedly pathological only in the neighbourhood of 0.20 ?second. In clinical work, i. e. in analysing individual cases, the upper or lower limit of the range of variation characteristic of the normal may perhaps be more useful. Means are in themselves not significant enough since a certain deviation from the normal must always be tolerated. In the individual case the question is how great a deviation can be tolerated.These sex differences in the electrocardiogram mentioned by earlier authors have in general not been confirmed and have not in any case been statistically significant.With the exception of pulse frequency, conduction time and systolic duration which reveal known variations with age no particularly marked differences between examined age‐groups have been noticed, except in the Q waves and in the waves in lead IV. BURNETT'S and TAYLOR'S (1936) statement that the amplitudes of the R waves increase during childhood reaching maximum at puberty has not been verified.Not rarely the Q waves attain amplitudes exceeding 25 per cent of the maximum amplitude of the QRS complexes. This is particularly common in lead III in which the Q waves occasionally exceed even half of the maximum amplitude of the QRS deflections. In place of these comparative measures which are often employed in interpretations of adult electrocardiograms means and their range of variation should be preferred. The Q waves in leads I and III decrease during childhood, the amplitudes being greatest in the 3‐years‐group.As in earlier investigations negative T in lead III has not seldom occurred (19.5 per cent of the total number of cases).As regards normal values of systolic duration ASHMAN'S formula, according to these cases, appears to yield fair conformity between calculated and observed means. The values of the Q–T interval and pulse period duration are graphically noted in accordance with ASCHENBRENNER and BAMBERGER (1935). Their investigations concerned infancy. The authors diagram (Fig. 18 page 163) thus gives supplementary figures of systolic duration for the rest of childhood.As regards the mean the direction of the electrical axis shows agreement with earlier investigations. Calculations of range of variation disclose distinct tendency towards the right in children between 3 and 13 years of age as compared with adults. According to these inquiries undoubtedly pathological right axis deviation should not occur at figures below 110°–120°. It should therefore be essential to measure, as a matter of routine, the direction of the electrical axis in examinations on children and not to differentiate between normal and pathological simply by means of estimating the aspect of the electrocardiogram. (Fig. 19, page 165).The thoracic lead has been registered in most cases, JEEVELL'S method being adopted. In conformity with earlier investigations the amplitudes show a considerably greater variation than in the standard leads. Q in the precordial lead was only registered in 4 cases, being infrequent in children. S in the precordial lead produces the greatest absolute mean and is, consequently, the main wave of this lead. Most amplitudes in the precordial lead present lower values in older children than in younger ones, the widest difference being noted in the girls in the 13‐years‐group who are differentiated by a chest volume greater than in other groups. The result conforms with earlier investigations according to which the amplitudes in the thoracic lead increase the smaller the distance between the surface of the thoracic wall and the heart.