Since NCX plays a crucial role under physiological circumstances in the maintenance of Ca2+ flux balance and SN pacemaking as well as in pathological settings, e.g., in arrhythmia generation (delayed afterdepolarizations, Ca2+ overload), selective inhibition of the exchanger became one of the most intensive research areas demanding the development of properly selective agents. The gene discussed is TLX2; the disease is Arrhythmia.