Shocking Results: AEDs Change Outcomes
The normal heart is a strong, muscular pump a little larger than a fist. It pumps blood continuously through the circulatory system. Each day the average heart beats 100,000 times and pumps about 2,000 gallons of blood. In a 70-year lifetime, the average heart beats more than 2.5 billion times.
These heart beats are the result of electrical signals coming from within the heart itself. Sometimes the heart’s electrical system goes askew. As a result it may beat very fast (tachycardia), or very slow (bradycardia). And sometimes the electrical system just stops; this is called sudden cardiac arrest (SCA).
Typically SCA is caused by either the large chambers of the heart quivering instead of contracting (ventricular fibrillation), or a rapid heartbeat that does not allow enough time for the heart to fill with blood before it contracts (ventricular tachycardia). Regardless of the cause, blood does not get pumped to the body, and survival depends on getting the heart beating correctly again within minutes. That’s when an electric shock to the heart — called defibrillation — is necessary.
Developments in defibrillation
Experiments with shocking the heart date back to the late 18th century, but the first successful defibrillation occurred in 1947. Cardiac surgeon Claude Beck used an experimental defibrillator he was developing on a 14-year-old boy whose heart stopped during surgery. The patient was saved, and Beck’s action sparked research into defibrillators.
In 1961, alternating current (AC) was used to stop ventricular tachycardia for the first time. Later that decade, we learned that direct current (DC) was more effective and safer than AC for defibrillation.
SCA doesn’t always occur in a hospital setting. The ability to bring the machine to the patient was paramount, and the first portable defibrillator was produced in 1965. In 1969, emergency medical technicians (EMTs) performed defibrillation without a doctor present for the very first time.
Early defibrillators produced a severe shock of up to 400 joules, which placed the patient at risk for cardiac injury and intense burns from the shock pads. The machines needed to be refined in order to better save lives without serious risk to the patient.
During the 1970s, safer prototypes were developed and tested in the Portland area. In the early 1990s, training and use of automated external defibrillators (AEDs) by police officers and other first responders began, and the FDA approved AED use by non-medical personnel in the 1990s. AEDs are portable devices capable of diagnosing certain arrhythmias and recognizing a rhythm that requires a shock.
Given the confusion of emergency situations, people may be reluctant to help a stranger in need for fear of legal repercussions should they make some mistake. To remove this fear, and thereby reduce bystanders’ hesitation to assist, many states have passed Good Samaritan laws offering legal protection to people who give reasonable assistance to those who are injured, ill, in peril or otherwise incapacitated. Not all states have them, and who and what they cover varies from state to state.
In the first five years of the new millennium, New York became the first state to mandate AEDs in schools and the Federal Aviation Administration mandated that all large, passenger-carrying U.S. airlines carry AEDs and have personnel trained in the use of them.
How AEDs work
An AED system consists of an AED device, battery, pad electrode, and if applicable, an adapter. They are very accurate and easy to use. With a few hours of training, anyone can learn to operate an AED safely. But training is not necessary; AEDs are intended for use by the general public. Modern AEDs use voice prompts, lights and text messages to guide the user through the process.
A built-in computer checks a victim’s heart rhythm through adhesive electrodes. The computer calculates whether defibrillation (a shock) is needed. If it is, a recorded voice tells the rescuer to press the shock button on the AED. This shock momentarily stuns the heart and stops all activity. It gives the heart the chance to resume beating effectively.
Recognizing and responding to sudden cardiac arrest
Symptoms of SCA can include a loss of responsiveness, irregular or absent pulse and no normal breathing when the head is tilted up. It is a leading cause of death in the United States. But when ordinary laypeople, excluding healthcare providers, are equipped with the skills to perform CPR and use AEDs, the survival rate can double — or even triple. Increasing the number of people trained in CPR and AED usage, establishing medical emergency response plans in schools and expanding access to AEDs are all critically important ways that we can increase SCA survival rates.
It is critical to apply an AED to the patient within the first three minutes of cardiac arrest. After approximately three to five minutes without a pulse, irreversible brain damage may begin to occur. For every minute that passes without CPR and defibrillation, the chances of survival decrease by 7 percent to 10 percent.
If an AED is not available, CPR should be performed while another person calls emergency services and attempts to locate an AED. AEDs are common in public places like airports, community centers, schools, government buildings and other public locations.
According to guidelines from the American Heart Association, all emergency personnel should be trained and allowed to use a properly maintained defibrillator. This includes all first-responding emergency personnel, both hospital and non-hospital.
To make quick defibrillation possible, a defibrillator must be immediately available to EMTs responding to a cardiac arrest. All ambulances and other emergency vehicles that respond to or transport heart patients should have a defibrillator.
Make it a point to learn where the closest AED is in your workplace and places you frequent, such as the gym. Someday someone’s life may depend on it.
Chain of Survival for Adults
It’s essential to integrate early defibrillation into an effective emergency cardiovascular care system. This means employing the five-part “chain of survival” concept.
- Immediate recognition of cardiac arrest and activation of the emergency response system — quickly calling 911.
- Early CPR with an emphasis on chest compressions — promptly giving cardiopulmonary resuscitation when needed.
- Rapid defibrillation — using the AED for rapid defibrillation as soon as it is available.
- Effective advanced life support — including airway management, ventilation support and treatment of rhythm disorders.
- Integrated post-cardiac arrest care — a comprehensive, structured, integrated, multidisciplinarysystemofcareshould be implemented in a consistent manner.