Source of rhythmic electrical impulses that trigger heart contractions. In the heart's electrical system, impulses generated at a natural pacemaker are conducted to the atria and ventricles. Heart surgery or certain diseases can interrupt conduction (heart block), requiring use of a temporary or permanent artificial pacemaker. A small electrode attached to an electric generator outside the body is threaded through a vein into the heart. The generator, inserted beneath the skin, produces regular pulses of electric charge to maintain the heartbeat. Permanent pacemakers can also be implanted on the heart's surface.
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