What purpose does an artificial pacemaker serve?

A pacemaker is a medical device which uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system.
It takes over the function of the sino-atrial node, that is the natural pacemaker of the heart. A pacemaker gives impulses so that the heart contracts and the blood flows out