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The first external pacemaker was designed and built by the Canadian electrical engineer John Hopps in 1950. A substantial external device, it was somewhat crude and painful to the patient in use. A number of inventors, including Paul Zoll, made smaller but still bulky external devices in the following years.
The first implantation into a human was made in 1958 by a Swedish team using a pacemaker designed by Rune Elmqvist and Åke Senning. The device failed after three hours. A second device was then implanted which lasted for two days. The worlds first implantable pacemaker patient, Arne Larsson, survived the first tests and died in 2001 after having received 22 different pacemakers during his lifetime. In February 1960, an improved model relying on better materials was implanted in Montevideo, Uruguay. That device lasted until the patient died of other ailments, 9 months later. The early Swedish designed devices used rechargeable batteries, which were charged by an induction coil from the outside.
Devices constructed by the American Wilson Greatbatch entered use in humans from April 1960 following extensive animal testing. The first patient lived for a further 18 months. The early devices suffered from battery problems - every patient required an additional operation every 24 months to replace the batteries.
The first pacemakers required wires (called leads) to be placed surgically on the outer surface of the heart. In the mid 1960s, the first transvenous leads were placed. This allowed the placement of pacemakers without opening the thoracic cavity and therefore without the use of general anaesthesia.
The first American-made nuclear-powered pacemaker was developed and implanted at Newark Beth Israel Medical Center in Newark, New Jersey.
In most cases, the indication for permanent pacemaker placement is a slow heart rate ( bradycardia) or a defect in the electrical conduction system of the heart (heart block) with associated symptoms. Typical symptoms of a slow heart rate include lightheadedness, poor exercise tolerance, and loss of consciousness. Individuals who have a slow heart rate but who are asymptomatic do not require a pacemaker. For instance, athletes typically have rest heart rates in the 40s without any deleterious effects.
If the slow heart rate is due to complete heart block, a pacemaker is indicated, since the heart rate can dramatically decrease without notice. Pacemakers can also be placed in patients at high risk for complete heart block.
Rarely, in people prone to ventricular fibrillation, a slow rhythm in the heart can lead to a ventricular fibrillation. In these people, preventing the slow rhythm can prevent ventricular fibrillation.
External pacemakers can be used for initial stabilization of a patient, but implantation of a permanent internal pacemaker is usually required for most conditions. External cardiac pacing is typically performed by placing two pacing pads on the chest wall. Usually one pad is placed on the upper portion of the sternum, while the other is placed along the left axilla, near the bottom of the rib cage. When an electrical impulse goes from one pad to the other, it will travel through the tissues between them and stimulate the muscles between them, including the cardiac muscle and the muscles of the chest wall. Electrically stimulating any muscle, including the heart muscle, will make it contract. The stimulation of the muscles of the chest wall will frequently make those muscles twitch at the same rate as the pacemaker is set.
Pacing the heart via external pacing pads should not be relied upon for an extended period of time. If the person is conscious, he or she may feel discomfort due to the frequent stimulation of the muscles of the chest wall. Also, stimulation of the chest wall muscles does not necessarily mean that the heart is being stimulated as well.