The congenital long QT syndromes from genotype to phenotype: clinical implications.

The long QT syndrome (LQTS) is a genetic disorder responsible for many sudden deaths before age 20. The identification of several LQTS genes, all encoding cardiac ion channels, has had a major impact on the management strategy for both patients and family members. Genotype-guided therapy allows more effective individually tailored therapy. Therapeutic options, including beta-blockers, left cardiac sympathetic denervation, and implantable defibrillators are discussed for patients of known and of unknown genotype. The recent identification of modifier genes which amplify the effect of an LQTS mutation may change the approach to risk stratification.