fullcortex.net

(1997)

An internal pacemaker is one in which the electrodes into the heart, the electronic circuitry and power supply are all implanted within the body. There are different kinds of pacemakers, but fundamentally they’re all designed to treat a heart rate that’s too slow. Some function continuously and stimulate the heart either at a fixed rate or at an increased rate during exercise. The device can be programmed to detect too long a pause between heartbeats and to then stimulate the heart.

Another device often confused with a pacemaker is an implantable (internal) defibrillator. Although it resembles a pacemaker, it has an entirely different purpose. It senses extremely rapid (and ineffective) heart rhythms such as ventricular tachycardia (rapid regular beating) or fibrillation (rapid irregular beating) that pose an immediate threat to life. The implantable defibrillator corrects the rhythm by special electrical pacing sequences or by sending a shock that may restore a normal heartbeat. Strictly speaking, these devices don’t restart a stopped heart. Unless effective heartbeat is restored, there is loss of consciousness followed by loss of life. These devices are implanted in a procedure similar to that used to implant a pacemaker. Many studies have demonstrated their effectiveness in treating serious disturbances of heart rhythm (arrhythmias).