Familial Heart Block and Sick Sinus Syndrome of Adult Onset

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Abstract
The case of 2 families are presented who showed familial occurrence of both complete heart block and sick sinus syndrome of adult onset. In 1 family (A), a 40 yr old man had intermittent advanced infra-His block of 2 yr duration and his uncle died of complete heart block which had lasted since he was 49 yr of age, while his father suffered from sinus arrest (SA) and his mother (a cousin of his father) and 2 siblings had sinus bradycardia (SB) with 1st degree A-V [atrio-ventricular] block. In the other family (B), there were 8 affected members in 2 generations. They consisted of a 50 yr old woman with bradycardia-tachycardia syndrome, her cousin with complete A-V block and narrow QRS interval combined with SA and 6 other members with SB. One member with SB, a 26 yr old daughter, also had WPW [Wolff-Parkinson-White] syndrome with attacks of paroxysmal atrial fibrillation. A literature review showed 26 families with familial complete heart block (FCHB) of adult onset including 8 families associated with congenital FCHB and 12 families with familial sick sinus syndrome (FSSS). Family A was similar to FCHB with SB and Family B was to FSSS. These familial disorders may be designated familial cardiac conduction disturbance (FCCD) because the affected region is not limited to a narrow area in the cardiac conduction system. Pathogenesis and clinical aspects of this familial disease were discussed.