Five Minute Primer on Defibrillation

A defibrillator is a device that sends electrical energy, or shock, to the heart. The aim of using a defibrillator is to treat cardiac arrest. The need for this generally arises when the patient has ventricular fibrillation or ventricular tachycardia, which are life-threatening arrhythmias that occur when contraction of the ventricles become abnormal. Defibrillators have electrocardiogram (ECG) leads and adhesive patches (or paddles). The adhesive electrodes are the patches placed on the patients chest that deliver the electric shock.

The History of Defibrillation

In 1899, two physiologists from the University of Geneva, Jean Louis Prevost and Frederic Batelli, discovered that small electric shocks could cause ventricular fibrillation in dogs. Later, in 1933, a device was invented to send an electric shock to the heart as a substitute for administering cardiac medications.

In 1947, the first defibrillation was carried out by Claude Beck who was a professor of surgery at Case Western Reserve University. The defibrillator he used had internal paddles that were placed on each side of the heart.

Before the end of the 1950s, defibrillation was successfully performed only when the chest cavity of the patient was open during the surgery. In this case, the defibrillator had electrodes in the shape of paddles so that flat ends could be placed on either side of the exposed heart.

As the 1950s gradually came to an end, the closed-chest defibrillator device was invented. One of the basic differences between the open and closed-chest devices was that the closed-chest defibrillators required more voltage for operation. It was invented by Dr. V. Eskin and A. Klomov.

Thus far, the defibrillators in existence used alternating current. In 1959, Bernard Lown began to develop new ideas to make the device more energy efficient. Lowns work led to the discovery of Direct Current (DC). Further development lead to the Biphase Truncated Exponential (BTE) waveform. With the BTE waveform, the defibrillators could use lower energy levels, which reduced the weight of the defibrillators that were later manufactured.

In the 1960s, Professor Frank Pantridge of Belfast began to introduce portable defibrillators for hospitals. This invention is now one of the most important tools that emergency medical services carry to resusitate people that suffer cardiac arrest. Portable units set forth the production of automatic defibrillatorsdevices with the ability to analyze heart rhythms.

The biphasic waveform did not completely replace the Lown waveform until the end of the 1980s. The waveform allowed defibrillators to work more quickly than the previous types. This in turn reduced the energy level needed for defibrillation. The success rate for treating cardiac arrest also improved.

In 1969, the research for making implantable cardioverter-defibrillator (ICD) began as a result of needing to provide adequate health care for victims of cardiac arrest. In 1980, the first implantable device was used at John Hopkins Hospital by Dr. Levi Watkins. Today, frequent victims of cardiac arrest are given the device for their aid at any time.

Types of Defibrillators

There are different kinds of defibrillators in use today. They include the manual external defibrillator, manual internal defibrillator, automated external defibrillator (AED), implantable cardioverter-defibrillator (ICD), and wearable cardiac defibrillator.

  • Manual external defibrillator: These defibrillators require more experience and training to effectively handle them. Hence, they are only common in hospitals and a few ambulances where capable hands are present. In conjuntion with an ECG, the trained provider determines the cardiac rhythm and then manually determines the voltage and timing of the shockthrough external paddlesto the patients chest.
  • Manual internal defibrillator: The manual internal defibrillators use internal paddles to send the electric shock directly to the heart. They are used on open chests, so they are only common in the operating room. It was invented after 1959.
  • Automated external defibrillator (AED): These are defibrillators that use computer technology, thereby making it easy to analyze the hearts rhythm and effectively determine if the rhythm is shockable. They can be found in medical facilities, government offices, airports, hotels, sports stadiums, and schools.
  • Implantable cardioverter-defibrillator: Another name for this is automatic internal cardiac defibrillator (AICD). They constantly monitor the patients heart, similar to a pacemaker, and can detect ventricular fibrillation, ventricular tachycardia, supraventricular tachycardia, and atrial fibrillation. When an abnormal rhythm is detected, the device automatically determines the voltage of the shock to restore cardiac function.
  • Wearable cardiac defibrillator: Further research was done on the AICD to bring forth the wearable cardiac defibrillator, which is a portable external defibrillator generally indicated for patients who are not in an immediate need for an AICD. This device is capable of monitoring the patient 24-hours-a-day. It is only functional when it is worn and sends a shock to the heart whenever it is needed. However, it is scarce in the market today.

When Not to Use a Defibrillator

Defibrillation is not indicated if the heart rhythm has completely stopped, as in asystole, or sometimes called flat line, or has pulseless electrical activity (PEA). Also, defibrillation is not indicated if the patient is conscious or has a pulse. Inappropriately given electrical shocks can cause dangerous arrhythmias, such as ventricular fibrillation.

Although defibrillators have specific indications and were initially exclusive to trained professionals, it is now possible to have one at home. Modern defibrillators are easy to use and do not require years of experience. In fact, a few tips from a health-care professional and a review of the the manual is all that may be needed to correctly intervene in a cardiac emergency. This development is helpful in reducing the number of death rates caused by sudden cardiac arrest and other heartbeat-related problems each year.


For more information on defibrillation and diseases that require a defibrillator, please visit the following websites:

Written by Sarah Gehrke, MSN, RN and last updated Aug 20, 2017 from Pacific Medical Training

For more information on defibrillators, visit Medical Device Depot.