Many people benefit from the implantation of cardiac pacemakers for management of certain cardiac dysrhythmias. These patients are seen regularly in the Emergency Department with a variety of pacemaker complications and malfunctions. The presence of a pacemaker may also affect management of unrelated medical problems. This, the second of a two-part series, covers the causes, diagnosis, and management of pacemaker malfunction; the pacemaker syndrome; the pacemaker Twiddler's syndrome; and other considerations in the paced patient including diagnosis of acute myocardial infarction, ACLS protocols, trauma, and sources of interference.