The importance of in vitro data in such studies is, for example, underscored in the study of Erlenhardt et al. [96], who identified the V759I mutation in HCN4, which had previously been identified in cases of sudden infant death syndrome [97] and sudden unexpected death in epilepsy in a patient with severe sinus bradycardia [98]. The gene discussed is HCN4; the disease is Sinus bradycardia.