Diffuse conduction abnormalities in an adolescent with familial sinus node disease.

We report a case of familial sinus node disease with associated conduction abnormalities in the atrioventricular node and distal conduction system Spontaneous atrial pacemaker activity was absent though the atrium could be depolarized. The pacemaker activity of the heart resided in the atrioventricular junction. The AV node showed impaired automaticity and abnormal conduction properties which partially improved after vagal blockage.