Sudden cardiac death is a major cause of mortality in industrialized countries. Since now more than 15 years, it is known that dysfunction of ion channels, which are small proteins important for the electrical activity of the heart, may cause fatal cardiac rhythm disturbances (arrhythmias). These human diseases that are caused by malfunction of ion channels are called "channelopathies". In this project, we will investigate new candidate genes that may be mutated in patients with cardiac channelopathies. These patients show severe cardiac arrhythmias, so-called long QT syndrome and Brugada syndrome, at young age, and may die suddenly because of mutations found in genes important for the heart function. The patients will be recruited in Ukraine, Russia, and Switzerland. After informed consent from the patients and their families, several new genes important for the cardiac electric activity will be analysed by the Russian team. The new mutations that will be found will be analysed by the Swiss team. The results of this project will permit 1) to demonstrate the causal relationship between the genetic variants and the pathology of the patients, 2) to perform more precise genetic counselling of the patients and family members, and 3) to better understand the genetic and molecular mechanisms underlying these complex cardiac diseases.