This document discusses cardiac pacemakers. It defines a pacemaker as a medical device that provides support to the heart's pacemaking system when it is not functioning adequately. It explains that pacemakers are needed when the sinoatrial node or atrioventricular node cannot generate a sufficient heartbeat. The document outlines the components of a pacemaker including electrodes, a power source, pulse generator, timing control, output driver, and sensing amplifier. It describes the different types of pacemakers such as internal, external, fixed rate, demand, and atrial or ventricular triggered models. Complications from pacemakers like pacemaker syndrome and embolism are also mentioned.