Inside a healthy heart, electrical signals travel in an orderly timed sequence to result in atrial contraction followed by a time delay and ventricular contraction. A surface or intracardiac electrocardiogram device can record these signals, and analysing the signals can identify healthy cardiac rhythms from irregular rhythms (cardiac diseases) caused by asynchrony of cardiac muscles.
An artificial pacemaker compromised of an electrical pulse generator, battery and lead can restore synchrony between cardiac muscles through delivering a rhythmic electrical stimulus to the heart muscle.
The first artificial pacemaker delivered 6 minutes of fixed-rate pacemaking using needle electrodes. The first modern pacemaker was fully implantable and operational