The natural pacemaker is the sinuatrial node, found at the base of the heart. The heart normally controls its rate and rhythm; heart block occurs when impulses cannot reach all parts of the heart. This may lead to ARRHYTHMIA, or even cause the heart to stop (see HEART, DISEASES OF). Artiﬁcial pacemakers may then be used; in the United Kingdom these are required for around one person in every 2,000 of the population. Usually powered by mercury or lithium batteries, and lasting up to 15 years, they are either ﬁxed to the outside of the chest or implanted in the armpit, and connected by a wire passing through a vein in the neck to the heart. Normally adjusted to deliver 65–75 impulses a minute, they also ensure a regular cardiac rhythm. Patients with pacemakers may be given a driving licence provided that their vehicle is not likely to be a source of danger to the public, and that they are receiving adequate and regular medical supervision from a cardiologist.
Although there are numerous possible sources of electrical interference with pacemakers, the overall risks are slight. Potential sources include anti-theft devices, airport weapon detectors, surgical diathermy, ultrasound, and short-wave heat treatment. Nevertheless, many pacemaker patients lead active and fulﬁlling lives.