[The vectorcardiogram of the normal child, 2-12 years of age (author's transl)].

Morphological aspects and the most important vectorial parameters of the VCG (Frank method) of normal children, aged 2 to 12 years, were analyzed. The total group consisted of 110 subjects (10 for each )ear) subdivided into three subgroups of progressive age. Semeiologic evaluation of the QRS in the frontal and sagittal planes was not significant because of the stereotypes of the figures. In the horizontal plane the majority of cases showed typical triphasic development of the vectorial groups, while biphasic morphology was found in the minority. The triphasic loop presented 1) a balance between anterior and posterior forces which was more frequent in the youngest children, 2) a posterior orientation which was more frequent in the oldest children or 3) an anterior orientation which was infrequent. Since the anterior orientation of triphasic QRS was not related to the age -- it may also be seen in normal adults -- it was attributed to a variation of ventricular activation. The biphasic loop was attributed to immaturity of ventricular conduction. The evaluation of quantitative parameters was in agreement with the results of other studies. The changes of initial and intermediate vectors were probably due to the more important development of the left ventricle. The QRS duration increased with age. The T loop was posterior in the majority of the youngest children and progressively advanced with age, although it remained posterior in an important number of cases of children aged twelve.