sentence: In addition to these widely investigated hereditary arrhythmia syndromes , there remain many other relatively less common arrhythmia syndromes , where researchers also have unraveled the genetic etiology , e.g ., short QT syndrome ( SQTS ) , sick sinus syndrome ( SSS ) , cardiac conduction defect ( CCD ) , idiopathic ventricular fibrillation ( IVF ) , early repolarization syndrome ( ERS ) .