Bauer A, Klemm M, Rizas KD, et al. - Through a prespecified substudy of EUropean Comparative Effectiveness Research to Assess the Use of Primary ProphylacTic Implantable Cardioverter Defibrillators which is a prospective, investigator-initiated, non-randomized, controlled cohort study conducted at 44 centers in 15 EU countries on 1,371 patients aged 18 years or older with ischaemic or non-ischaemic cardiomyopathy and decreased left ventricular ejection fraction (≤ 35%), experts postulated that periodic repolarization dynamics, a novel marker of sympathetic-activity-associated repolarisation instability, could be employed to recognize electrically vulnerable patients who would profit from prophylactic implantation of implantable cardioverter defibrillators (ICDs) by way of a decrease in mortality. In contemporarily treated patients with ischaemic or non-ischaemic cardiomyopathy, periodic repolarisation dynamics prognosticated mortality decreases related to prophylactic implantation of ICDs. Moreover, periodic repolarization dynamics could aid in guiding treatment decisions about prophylactic ICD implantation.