The Romano-Ward long QT syndrome, an autosomal dominant inherited disorder, is 
an increasingly recognized cause of sudden cardiac death in children and adults. 
Sudden death may or may not be preceded by a history of "seizures" and recurrent 
syncope; the diagnosis relies on electrocardiographic evidence, including 
prolongation of the QT interval corrected for heart rate, T wave abnormalities, 
sinus bradycardia, and polymorphous ventricular tachycardia (torsades de 
pointes). Recently, a gene responsible for causing long QT syndrome was 
localized (using molecular genetic methods) to the short arm of chromosome 11 
(11p15.5) in the region near the Harvey ras-1 locus. The purpose of this report 
is to describe the current molecular genetic understanding of long QT syndrome, 
including information regarding gene mapping, genetic heterogeneity, and 
prenatal or presymptomatic diagnosis.