The following is a personal study of the case histories of 3 patients, spontaneous carriers of "labile pseudo-ischemic T wave" and of their direct consanguineous, a total of 25 subjects. In these three families the family incidence on electrocardiographic anomalies is confirmed. In these same subjects as well as in others belonging to families examined in a previous study, a total of 90 subjects, the duration of the QT interval was measured, showing values which tended to be above the average and, in some cases, above the accepted maximum. The analogy among the anomalies of the ventricular repolarization to be found during the course of neurological diseases and under experimental conditions of unilateral lesions of the sympathetic cardiac innervation and the "labile T wave" syndrome, sometimes coexisting in the same family with a report of elongated QT interval, suggests the hypothesis that this may be placed within the ambit of disgenetic syndromes from alterations of the functional balance between right and left component of the sympathetic heart innervation.