Idiopathic ventricular fibrillation in patients with an electrocardiogram (ECG) 
pattern of right bundle branch block and ST-segment elevation in leads V1 to V3 
(now frequently called Brugada syndrome) is associated with a high incidence of 
syncopal episodes or sudden death. The disease is inherited as an autosomal 
dominant trait. Mutations in SCN5A, a cardiac sodium channel gene, have been 
recently associated with Brugada syndrome. We have analyzed 7 patients from 
Israel affected with Brugada syndrome. The families of these patients are 
characterized by a small number of symptomatic members. Sequencing analysis of 
SCN5A revealed two novel mutations, G35S and R104Q, in two Brugada patients, and 
a possible R34C polymorphism in two unrelated controls. No mutations were 
detected in 5 other patients, suggesting genetic heterogeneity. Low penetrance 
is probably the cause for the small number of symptomatic members in the two 
families positive for the SCN5A mutations.