INFLUENCE OF AGE, SEX, AND BODY HABITUS ON THE MEAN QRS ELECTRICAL AXIS IN CHILDHOOD AND ADOLESCENCE

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Abstract
The electrocardiograms of 883 normal children between the ages of 6 months and 20 years were studied and the mean QRS axes were calculated. The average QRS axis for all age-groups was 66.95[degree]. The range of values found (-60[degree] to + 134[degree]) was considerably wider than that usually accepted as normal. A consistent percentage (15.8%) of subjects in each age-group had axes greater than 90[degree] and in the total group 1.8% had axes of less than 0[degree]. A set of means and standard deviations for each age-group has been prepared. Variations in these values are apparent with age, but no significant difference in the mean axis was noted between the sexes at any one age or for any age-group. Attempts have been made to correlate the trends in axis with body build. Such correlation was statistically significant only during age periods of rapid longitudinal growth. The overall leftward trend throughout childhood was confirmed. Because of the wide range of normal values, it is evident that cardiac abnormalities cannot be diagnosed on the basis of axis alone, but the mean QRS axis may be a valuable adjunct to diagnosis when combined with study of the precordial leads.