Reginald T. Ho et al. JACEP 2016;j.jacep.2016.08.006 Idiopathic Ventricular Fibrillation Arising From the Moderator Band (A) Multiple tightly coupled (280 ms) premature ventricular contractions (PVCs) triggering ventricular fibrillation (VF). (B) CARTOSOUND image of the right ventricle showing the PENTARAY catheter (Biosense Webster, Diamond Bar, California) on the moderator band–papillary muscle complex. Purkinje potentials (PPs) (white arrows) correspond to gold tags on the PENTARAY. (C) A high-frequency PP (second black arrow) precedes PVC onset by 103 ms prior to radiofrequency application. Reginald T. Ho et al. JACEP 2016;j.jacep.2016.08.006 American College of Cardiology Foundation