[Present concepts of congenital long QT syndrome]

The congenital long QT syndrome is characterised by the presence of syncopes due to torsades de pointe which may degenerate to ventricular fibrillation and cause sudden death. These syncopes occur in young subjects with electrocardiographic abnormalities and prolongation of the QT interval. Patients with the autosomally dominant transmitted Romano-Ward syndrome with normal audition are classically opposed to those with the Jervell and Lange-Nielsen autosomally recessive syndrome who have bilateral total deafness. Our understanding of the congenital long QT syndrome has improved in recent years with respect to the physiopathology, diagnosis and treatment, due to research in the fields of genetics, electrocardiography and electrophysiology. The diagnosis is based on analysis of the phenotype and genotypes. A family enquiry is always necessary to detect unrecognised forms. Five culprit genes have been identified for the Romano-Ward syndrome. All code for subunits of sodium or potassium channels: two a subunits of the potassium channels (QVLQT1 for LQT1, HERG for LQT2), the a subunit of the sodium channel INa (SCN5A for LQT3), and two regulatory subunits of potassium channels (KCNE1 for LQT5 regulating the KvLQT1 channel and MiRP1 regulating HERG). The concept of genetic heterogeneity of the congenital long QT syndrome may thus be understood: different genes may be responsible for the same phenotype. Except for specific cases, the usual treatment is life-long betablocker therapy and the avoidance of a large number of drugs, the list of which is continually updated. A multicentre trial is underway to validate betablocker therapy for the prevention of cardiac events in a LQT1 genotype population. Prospective studies will be necessary to assess gene-specific treatments.