BACKGROUND: both congenital and acquired factors may cause QT interval prolongation. Congenital factors include mutations in the human cardiac ether-a-go-go-related gene (hERG), which encode potassium channel proteins.  Activity of this ion channel is crucial for repolarization of cardiac muscle during every heartbeat.  Additionally a wide variety of drugs from diverse chemical scaffolds block the hERG channel. Among the drugs that can cause QT prolongation, the more common ones include antiarrhythmics (especially Class 1A and Class III), anti-psychotic agents, anti-histamine and certain antibiotics.

Such findings have lead to a recommendation from the ICH that all new drugs be tested in assays to assess hERG block liability/involvement before they are administered to humans. Among the assays, patch-clamp studies can provide valuable information regarding the effects of a test substance towards hERG, and ion channels that contribute to cardiac Action Potential. Patch-clamp assays frequently use powerfull heterologous expression system: the ion channel cell lines.