RESUMEN
The authors described seven cases of supraventricular tachycardia with atrio-ventricular dissociation, associated with the activity of an automatic focus in the bundle of His. These tachycardias, which appear at birth or are discovered at a very young age, appear to be congenital and sometimes familial, and are always isolated, having no associated cardiac abnormality. They give rise to cardiac failure, which is more marked when the rate is high (180-260/mn) and particularly resistant to treatment. The most effective form of treatment is amiodarone, almost always used in combination with digitalis. The anatomical abnormality, which was studied in the first case, is a contricting fibrosis around the main trunk of the bundle of His, and the appearances are reminiscent of those found in conditions of congenital atrio-ventricular block.