Hereditary prolongation of the Q-T interval. Genetic observations and management in three families with twelve affected members.

Three families with the prolongation Q-T interval are described. Two demonstrated the nonsex-linked dominant mode of inheritance of the condition without neural deafness (the Romano-Ward syndrome). Family A had four affected members in three generations. Family B had three affected members in two generations, but the parents of the affected children were distant relatives. Family C had five affected members in three generations. Of the nine living affected members, seven were asymptomatic and never experienced syncope. The remaining two, aged 7 and 9 years, respectively, had multiple syncopal attacks. Of three affected members who died, two had electrocardiograms before death. The thirds, an apparently healthy boy of 14 years, had a single syncopal attack 13 months before he died in his sleep. The nature of the dysrhythmia causing syncope was documented in two cases. One of the affected children was treated successfully with a permanent demand pacemaker and propranolol, the other with propranolol alone. The electrophysiologic findings and the management of both symptomatic and asymptomatic patients are discussed.