Defibrillator electrodes deliver controlled electric shocks to return a heart to its normal rhythm. Early designs were ovoid metal discs that ran on alternating current, but later designs used direct current and relied on banks of capacitors. Portable defibrillators have revolutionized emergency response, and implantable cardioverter defibrillators can automatically issue a corrective charge. The placement of defibrillator pads is important for restoring normal rhythm.
Defibrillator electrodes, often referred to as paddles, are conductors that deliver a powerful but controlled electric shock designed to return a heart to its normal rhythm. They are connected via wires to a power source capable of providing an adequate charge for a given situation. Defibrillator pads come in a number of designs, including ones that attach directly to the heart muscle and others that attach to the outside of the chest.
The first defibrillators were invented in the early 20th century by Swiss scientists who realized that controlled electric shocks could stop and restart a heart. Until 20, defibrillator electrodes could only be used directly on the heart during surgery in which the chest cavity was open. These early electrodes were ovoid metal discs about the diameter of a hockey puck and ran on alternating current (AC) directly from a wall outlet.
Later, in the 1950s, defibrillators using direct current (DC) were developed. These designs relied on banks of capacitors that were charged and could deliver a more controlled shock of predictable length and power. DC-powered defibrillators are still the standard design, although refinements to the actual electronic pulses have greatly reduced power consumption as well as the risk of burns and other tissue damage when the shock passes through the defibrillator electrodes.
Such advances allowed defibrillators to be much less bulky, and the first portable models hit the market in the 1960s. They were quickly adopted as standard equipment by ambulances and first responders, and portable defibrillators have radically changed the outlook for people with heart problems. In the event of a cardiac arrest, modern defibrillator pads can restore a normal heartbeat 90% of the time on the first charge.
For individuals with a history of heart problems, an implantable cardioverter defibrillator (ICD) may be surgically inserted into the chest cavity. Similar in mechanism to the very first defibrillators, its electrodes are attached directly to the heart muscle. The complex electronics can detect irregular rhythms and cardiac arrests and also automatically issue a corrective charge.
Where the defibrillator pads are placed has a lot to do with how well the charge will restore the rhythm to normal. The two recommended arrangements are anterior-apical placement and anterior-posterior placement. Anterior-spical placement is preferred for external defibrillators and anterior-posterior placement is recommended for internal devices. For permanently implanted devices, precise measurements of the heart muscle are taken to ensure an optimal fit.
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