Pacemaker. Coloured X-ray of a pacemaker (right) implanted in the chest of a 66-year-old male patient to treat heart failure (cardiac insufficiency). A pacemaker is used to maintain a patient's heart rate. It does this by generating and delivering electrical impulses through electrodes (thin, white, lower left) to contract the heart muscles and regulate the electrical conduction system of the heart. Usually artificial pacemakers are used because the heart's natural pacemaker is not fast enough, or because there is a block in the heart's electrical conductive system.