[The vectorcardiogram of the normal child, 2-12 years of age (author's transl)]. / Il vettorcardiogramma del bambino normale dia 2 ai 12 anni di eta'

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.

Possible role of a ventricular conduction disturbance in the electrogenesis of the ECG-VCG signs of myocardial infarction.

The typical QRS patterns of myocardial infarction (MI-QRS) are commonly attributed to myocardial cellular death. However, observation of a transient appearance of MI-QRS during coronary insufficiency, the disappearance of MI-QRS after coronary by-pass surgery and the appearance of MI-QRS after intracranial hemorrhage suggest that a different electrophysiological mechanism may be at work. There is a single convincing explanation for all these observations. It seems possible, at least theoretically, that a localized conduction disturbance can generate or contribute to the generation of the MI-QRS. The results obtained in nine out of 194 cases studied by means of premature right atrial stimulation (PRAS) in our laboratory seem to confirm this hypothesis. In five of them we observed typical MI-QRS in the aberrant beats which were absent in the basal tracings. In the other four cases, MI-QRS which were present in basal tracings disappeared in the aberrant beats. In three of these a reduction in the duration of QRS was also observed, while in the fourth the duration of QRS did not change. In no case could the alterations of QRS (induction or disappearance of MI-QRS) be explained by a classical conduction disturbance, preexcitation or by a premature ventricular beat. While the induction of MI-QRS was clearly due to an aberrant conduction in the supraventricular beats, the disappearance of basal MI-QRS changes in premature supraventricular beats is more difficult to explain. One possible electrophysiological mechanism could be a supernormal phase conduction. If this is the case, the basal MI-QRS could be due to a ventricular conduction disturbance. In conclusion, our results suggest that MI-QRS can be generated, at least in our cases, by a localized conduction disturbance.