Pacemakers and implantable cardioverter/defibrillators (ICDs) are fascinating little machines.  They were first placed in survivors of sudden cardiac death in 1980, and over the past several decades have become more complex with increasing abilities to sense, pace and defibrillate.  As the population ages and the prevalence of cardiovascular disease increases, patients with pacemakers and ICDs will present more commonly to the emergency department.  It is imperative that the emergency provider have a framework for troubleshooting these devices.  This post will briefly review the use of the "donut" with an implantable pacemaker, as well as three pacemaker malfunctions the emergency provider may encounter.