Familial combined sinus node and atrioventricular conduction dysfunctions.

Eighteen members of a family were investigated for cardiac conduction abnormalities following the discovery of a second-degree atrioventricular block in a fetus at 35 weeks of gestation. The conduction disturbance was diagnosed by ultrasonography. Seven of the family members were diagnosed as suffering from sinus node dysfunction and/or various degrees of atrioventricular block. Three of them were children aged 9 months to 6 years and all were asymptomatic. The symptomatic family members were two adults. One of them had a pacemaker inserted for a complete atrioventricular block and Adam-Stokes attacks while the other had had several fainting attacks. The clinical, electrocardiographic and ultrasonographic findings of the family members are presented. Previous reports in literature have documented the dominant transmission of familial sinus node dysfunctions or of familial cardiac conduction disturbances. The coexistence of both dysfunctions in the same family has not been emphasized in previous reports. A review of these previously reported families, as well as our patients, suggests the need of investigation and follow-up of the families in which one member of any age is diagnosed as suffering from an "idiopathic" disturbance of the cardiac conduction system.