Once limited to discussions of the Jervell and Lange-Nielsen syndrome and 
Romano-Ward syndrome, the long QT syndrome (LQTS) is now understood to be a 
collection of genetically distinct arrhythmogenic cardiovascular disorders 
resulting from mutations in fundamental cardiac ion channels that orchestrate 
the action potential of the human heart. Our understanding of this genetic 
"channelopathy" has increased dramatically from electrocardiographic depictions 
of marked QT interval prolongation and torsades de pointes and clinical 
descriptions of people experiencing syncope and sudden death to molecular 
revelations in the 1990s of perturbed ion channel genes. More than 35 mutations 
in four cardiac ion channel genes--KVLQT1 (voltage-gated K channel gene causing 
one of the autosomal dominant forms of LQTS) (LQT1), HERG (human ether-a-go-go 
related gene.) (LQT2), SCN5A (LQT3), and KCNE1 (minK, LQT5)--have been 
identified in LQTS. These genes encode ion channels responsible for three of the 
fundamental ionic currents in the cardiac action potential. These exciting 
molecular break-throughs have provided new opportunities for translational 
research with investigations into genotype-phenotype correlations and 
gene-targeted therapies.