[Familial sick sinus syndrome. Observations on three cases studied (author's transl)].

Three siblings with sick sinus syndrome (SSS) are described. In each case, electrocardiogram, Hisian electrogram and sinus node recovery time were recorded, both in basic conditions and under the effect of drugs. In two cases a permanent pacemaker uas applied. The clinical and instrumental investigations were extended to 24 out of 33 cases included in the complete genealogical tree; three cases with arrhythmias were identified (atrial and ventricular extrasystoles and atrial fibrillation). From a genetic point of view, the SSS seemed to segregate a dominant autosomic character with a lower frequency of the disease in the descendants then expected, which is probably due to their low age.