Syncope in childhood: a case control clinical study of the familial tendency to faint.

We investigated the possibility of an inherited tendency to faint by studying 30 consecutively referred well children with vasodepressor or vasovagal syncope. The family history of each patient was reviewed for syncope and for 24 cases was compared with the family history of the child's best friend. None of the best friends had syncope. 27/30 cases and 8/24 best friends had at least one first degree relative with syncope (p less than 0.01). Of the 8 best friend controls with a parent or sibling with syncope, the mother was affected in 7; 4/7 of these mothers had first degree relative(s) with syncope. In 11/30 patients both a sibling and parent had syncope compared with 1/24 of control families (p less than .01). We conclude that there is an inherited tendency to faint since most children who faint have a first degree relative who faints, a useful fact in differential diagnosis. This inherited tendency may be multifactorial but requires an environmental stimulus for expression.