Defibrillation is commonly used to treat patients who have a severe and immediate heart condition within the following realms: arrhythmia; dysrhythmia; fibrillation (hence the name of both process and unit); and tachycardia. All of the above conditions are basic variants on the idea that the heart may beat in rhythms other than its natural one, or that it may have potentially fatal pauses to its normal rhythm. Defibrillation induces a return to natural rhythm, or attempts to do so.
The treatment is given by means of a number of processes. It works, when it works., by introducing a therapeutic electrical charge to the heart using a defibrillator. This machine may be applied either externally or internally.
The most common device, or at least the one most commonly encountered by non medical professionals, is the external machine. This consists of a charging pack, with a display that tells the operative how much voltage is being applied and whether the heart is beating, and a pair of paddles – electrical contacts, which are applied at strategic points on the torso to send the charge into the heart.
The paddles must first charge with the correct voltage, and are then applied – effectively giving the patient an electric shock, which it is hoped will stimulate the heart either to resume beating or to settle down into its normal rhythm of beat.
Rarely seen (because when in operation they are inside the body) are implantable defibrillators. These are used both to diagnose and to treat a number of life threatening changes to the heart’s rhythm. They are not pacemakers in and of themselves – although they can be used to perform the function of a pacemaker in addition to their normal duties.
An internal device may be indicated where a patient has a condition that will repeatedly cause arrhythmias to occur in the ventricles. It may also, however, constitute a threat to life in and of itself. If the device fires at the wrong time, having wrongly detected a change in heart rhythm, it can cause the heart to go into the shock or attack mode that it has been implanted to prevent.
The device has a long history – it was first used, or given in demonstration, in the late 19thcentury. The first commonly used machine, which was nothing like the one we use today, was invented in the 1930s, and consisted of a hollow needle that extruded a wire onto the heart, whereby the shock could be administered.
The “closed chest” defibrillator was invented and first used in what was then the USSR, in the 1950s. This machine was conceived as an alternative to open heart shocking, which was previously the only way to get electricity to the cardiac valves. The leap in technology was facilitated by the ability to create greater voltages in safety – to the operator as well as to the patient. In its modern form, this paddle device is still used (as noted) today.
Originally, the machine used an alternating current. In the late 1950s (1959), Bernard Lown proved that it was possible to create a single charge, using a direct current, of 1,000 volts, which could then be delivered in a single jolt through the body of the patient. This method supersede the use of AC and is still employed today. In the 1960s, such units were made portable and the modern machine was born.
Smith is a paramedic. He has written a book explaining how the defibrillator kicks the heart into action again.