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An implantable pacemaker, also known as an artificial pacemaker, is an internal medical device that regulates the beating of the heart to a sufficient rate that meets the body's needs. This type of pacemaker is used in patients whose heart rate is too fast, a condition called tachycardia; whose heart rate is too slow, which is called bradycardia; or who have a blockage that prevents the heart's electrical conduction system from working properly. An implantable pacemaker works by sending electrical impulses via electrodes to the heart, stimulating the heart to contract and thus regulating the heartbeat. An implantable defibrillator is often used in conjunction with an implantable pacemaker in order to prevent cardiac arrest.
Although external pacemakers had existed since 1950, Rune Elmqvist and Áke Senning invented the first internal pacemaker in 1958 at the Karolinska Institute of Solna, Sweden. Arne Larsson was the first recipient of their creation. This implanted pacemaker only lasted three hours, and Larsson went on to receive 25 more pacemakers before his death in 2001. Subsequent implantable pacemaker designs did not have lengthy lifespans because of technological barriers in power sourcing. Early pacemakers typically relied on a mercury battery, but Wilson Greatbatch's invention of the lithium-iodide cell greatly increased a pacemaker's life span and became the standard energy source for modern implantable pacemakers, which usually last five to 10 years.
There are three chief types of implantable pacemakers: single-chamber pacemakers, dual-chamber pacemakers and rate-responsive pacemakers. Single-chamber pacemakers, also known as ventricular demand pacemakers, have one lead wire, or pacing lead, that can connect to either the right atrium or right ventricle of the heart. These pacemakers send electrical impulses to the heart only as necessary, or on the heart's demand. Dual-chamber pacemakers have two pacing leads, one lead for the atrium and the other for the ventricle, in order to more closely mimic the natural pacing of the heart. Rate-responsive pacemakers, which might be either single-chambered or dual-chambered, use sensors to adjust pacing according to the user's activity level.
Recipients of implanted pacemakers should not notice a considerable change in their lifestyles, although there are a few things they should avoid. Pacemaker users must avoid strong magnetic fields that can interrupt pacemaker function, including magnetic resonance imaging (MRI) scans or arc welding. Full-contact sports are also not recommended, because contact with the area surrounding the pacemaker can cause severe discomfort. Most home appliances and cell phones, however, have been proved to be safe around pacemaker recipients. All pacemaker users should undergo periodic checkups to make sure that the devices function properly.