Genetic defects of cardiac ion channels. The hidden substrate for torsades de pointes.

The novel insights provided by the molecular genetic applied to the study of cardiac arrhythmias have just started to scratch the surface of the complex relationships between the genetic abnormalities of ion channel structure and the susceptibility to life threatening ventricular arrhythmias. These crucial pieces of information that are being gathered may have broader implications than those concerning the relatively restricted field of inherited arrhythmogenic diseases. An area of possible crucial application of the molecular genetic of cardiac ion channels, is the so-called drug-induced Torsade de Pointes (TdP) and acquired Long QT Syndrome. This condition is defined as an abnormal response to the administration of a variety of drugs which, in susceptible subjects, may induce an excessive QT interval prolongation and possibly lead to the onset of life-threatening ventricular tachyarrhythmias (drug-induced TdP). The "proof of concept" that sub-clinical variants of the inherited long QT syndrome may play a causative role has been recently brought to light. However, large population-based studies are still needed in order to quantify the epidemiological relevance of such findings. The future developments in this area of research will lead to the availability of pre-prescription genotyping for the identification of the susceptible subjects and to the development of safer drugs.