A normal, healthy heart uses electrical impulses to pump oxygenated blood around the body where it is needed. Through a continuous rhythm of polarization and depolarization, the heart's natural pacemaker allows blood to be pumped throughout the body to the vital organs and tissues. Consequently, you can view these electrical impulses as the waves often seen on electrocardiogram (ECG) machines.
Cardiac issues like sudden cardiac arrest (SCA), also known as heart attacks, are a major global burden, contributing to 15-20% of all natural deaths in adults in the USA and Western Europe and 50% of all cardiovascular deaths. SCA happens in variety of ways, inherited or acquired. For example, someone may be born with a congenital heart defect or develop coronary heart disease later in life.
When heart attack occurs, a person's heart has a problem with its electrical signal, causing irregular heartbeats. When the heartbeat is erratic, the heart cannot pump blood effectively through the body. Noticeable symptoms manifest in several ways. When blood stops flowing to the brain and other vital organs, the person suddenly collapses and becomes unresponsive. Their pulse and breathing become undetectable. If not treated within minutes, the person may die.
Awareness of and quick access to an automatic external defibrillator (AED) could make a significant difference in survivorship of the affected. A defibrillator, which is a type of medical device named for its most common usage reason (treating ventricular fibrillation), works by delivering a controlled shock to the person's whole heart system. This is meant to momentarily disrupt the erratic electrical activity, allowing the heart to reboot on its own and reestablish its natural, proper rhythm.
AEDs are becoming more available in public spaces of countries with more modern infrastructure. An AED contains four main components.
· Electrode pads, which deliver the potentially lifesaving shock after attaching to the patient's chest
· A processor that analyzes and decides whether a patient requires a shock
· A battery which charges a capacitor
· The capacitor stores the voltage that releases energy to shock the patient
Public access AEDs can be easily spotted if you know what you're looking for. It is usually found in a wall-mounted AED cabinet or a wall-bracketed box. In the box, there will be the electrode pads and the AED machine itself. The machine will come with instructions, and depending on the sophistication of the AED, may even have audible instructions and guidance. You may also find a towel and razor to dry the skin and remove any body hair if necessary, before attaching the pads.
Once the pads are attached in the right places on the person's body, your involvement in delivering the shocks will be minimal. The AED will monitor the person's heartbeat and tells you whether a shock is needed or not. A semi-automatic defibrillator will require the bystander to press a button to deliver the shock. A full automatic defibrillator will deliver the shock on its own.
Not all arrhythmias benefit from an AED shock, and sometimes the person may require more than one shock. However, a common misconception is that defibrillators can restart a heart that has already stopped creating its own electrical pulse. This is not true - a heart in asystole, aka flat-lining, is unlikely to be revived.
Other common hesitations around AED usage include fear of using adult-sized electrode pads on small children and babies (the higher voltage did not cause more harm), and potential embarrassment of exposing and attaching electrode pads on people with breasts (AEDs work the same way on people with breasts and no one should delay this life-saving treatment).
Findings from recent studies suggest that the incidence of bystander intervention utilizing an AED is relatively low, meaning low survival rates as well. However, everyone can benefit from education and training on how to safely operate an AED, which is typically used in conjunction with high-quality cardiopulmonary resuscitation (CPR).
Sources:
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3. Defibrillator Voltage: How it Works - Avive AED. avive.life. Published November 9, 2023. https://avive.life/blog/defibrillator-voltage/
4. How Does a Defibrillator Work? | Steroplast Healthcare. www.steroplast.co.uk. https://www.steroplast.co.uk/knowledge-base/how-do-defibrillators-work.html
5. Partners C. A Brief Explanation of What a Defibrillator Really Does. Cardio Partners. https://www.aed.com/blog/a-brief-explanation-of-what-a-defibrillator-really-does/
6. Tejman-Yarden S, Katz U, Rubinstein M, et al. Inappropriate Shocks and Power Delivery Using Adult Automatic External Defibrillator Pads in a Pediatric Patient. Pediatr Emerg Care. 2021;37(12):e1708-e1710. doi:10.1097/PEC.0000000000001074
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