An AED, automated external defibrillator, is a portable medical device used to deliver a controlled electrical shock (defibrillation) to assist the heart back into a normal rhythm during a Sudden Cardiac Arrest event. 

Automated = carried out by machines or computers without needing human control 

Defibrillator = a device that gives a high energy electric shock to the heart of someone who is in cardiac arrest 

The first external defibrillator was developed in 1930 at the Johns Hopkins University by electrical engineer, William Kouwenhoven, the father of CPR. After a three-decade span, the external defibrillator was fine-tuned by cardiologists, cardiac surgeons, engineers, and more. Eventually in the early 1960s, Professor Frank Pantridge developed the very first portable AED.  

Although this portable AED was in existence, it would still be many years before AEDs became available to the public. In 1978 the first commercially available AED was developed, designed for lay rescuers. 

Before we get into how exactly the AED works, let’s get a solid understanding of how the magnificent pumping machine within our chest actually works. 

The heart has a cardiac conduction system, an electrical system controlling the heart’s rate and rhythm of the beat. During each heartbeat, an electrical signal migrates from the top to the bottom of the heart, creating a systematic rhythm. The electrical signal causes the heart to contract and pump blood, supplying oxygen and nutrients to other systems in the body for optimal function. 

Fibrillation = an abnormal and erratic twitching of the heart muscle 

There are many causes for fibrillation to occur (See our previous post Are You At Risk?). The most common cause of Sudden Cardiac Arrest is an irregular heart rhythm called ventricular fibrillation. Rapid, erratic heart signals cause the lower heart chambers to quiver instead of pumping blood. In turn, this causes an erratic heartrate and loss of oxygen supply leading to the known collapse response during an SCA event. 

The AED can analyze the heart’s rhythm and, if necessary, deliver an electrical shock, or defibrillation, to allow for normal rhythm. Some symptoms of Sudden Cardiac Arrest are sudden collapse, no pulse, no breathing, and loss of consciousness. Some symptoms prior to SCA are chest discomfort, shortness of breath, weakness, (fast-beating, fluttering, or pounding heart) called palpitations, or nothing at all. 

Most AEDs are designed to guide bystanders, coworkers, and other lay rescuers through a rescue using voice, text or illustrations. When an emergency occurs and you observe any of the symptoms mentioned above, follow these steps: 

  1. Call 9-1-1 immediately and send another bystander to find the closest AED. 
  2. Check to see if the victim is struggling to breathe or responsive. If the victim is unresponsive, start performing CPR immediately to maintain blood flow to vital organs. 
  3. When the AED arrives, attach the electrode pads to the victim following the AED guidance. Once connected, the AED will automatically analyze the victim’s heart rhythm or ask you to push a button to start the analysis. Don’t touch the victim while the AED performs this analysis. Not all SCA victims require a shock immediately, and the AED will let you know what to do next. It may advise you to press a button to administer a shock, or it may automatically administer one. Be sure to follow the visual or audio prompts. 
  4. After a shock is delivered, the AED will instruct you to continue performing CPR. Some AEDs will measure the rate and depth of your compressions and will instruct you to adjust what you’re doing to deliver high-quality CPR. Follow the AED prompts to improve CPR quality. 
  5. Continue administering CPR and following the prompts on the AED until emergency personnel arrive. 
  6. If you notice obvious signs of life, discontinue CPR and monitor breathing for any changes in condition. 

Knowledge is empowering when it comes to helping a Sudden Cardiac Arrest victim. Subscribe to our blog to stay educated about SCA!